Jakob von UexkŸllÕs Concept of Umwelt as an Account of the Mental 

Chapter 1: Introduction 
1.1 The worlds of others 
In the Þrst decade of the 20th century, a horse named ÔClever HansÕ captured the international attention of scientists and the public alike (Kšchy 2020: 1-5, Crawford 2021: 1-4). Its owner Wilhelm von Osten had made remarkable claims about the horseÕs cognitive abilities, claiming to have trained it to be able to perform basic arithmetic, recognize people in photographs, and indicate the values of playing cards and coins. All of this, the horse allegedly indicated by tapping out the answers with its hoof (Kšchy 2020: 2). Clever Hans attained considerable international celebrity, with a New York Times headline calling him ÒBerlinÕs Wonderful Horse; He Can Do Almost EverythingÓ (Crawford 2021: 1). A Þrst commission of experts found no signs of scientiÞc deceit or circus tricks and could provide no alternative explanation for Clever HansÕ performance than the attribution of considerable cognitive abilities which so excited the public (Kšchy 2020: 3). A second, smaller committee made up of the renowned psychologist Carl Stumpf and his assistants Erich von Hornborstel and Oskar Pfungst was Þnally able to dispel the mystery scientiÞcally: Pfungst devised experiments in which the humans interacting with the horse did not know the correct answer themselves and Clever Hans was completely unable to answer questions correctly under these conditions (ibid. 3-4). The explanation that Pfungst provided for the impressive previous performances was that the horse was picking up on very subtle behavioral cues from its handler and adjusting its hoof-taps to those cues rather than to any question presented (ibid. 4). 
While less sensational than the original reports, the story of Clever Hans and the eventual debunking of his alleged intelligence has itself become a popular anecdote for illustrating the di.iculties we humans face when studying minds di.erent from ours, and our propensity to project anthropomorphic psychological categories on subjects or systems very di.erent from ourselves. This is the function the anecdote of Clever Hans plays e.g. as the opening section to two very di.erent books, Kristian KšchyÕs (2020) Beseelte Tiere: Umwelten und Netzwerke der Tierpsychologie [Ensouled Animals: Environments and Networks of Animal Psychology] and Kate CrawfordÕs (2021) Atlas of AI Power, Politics, and the Planetary Costs of ArtiÞcial Intelligence. In the case of AI, the name Clever Hans has been used to highlight a problem otherwise known as data leakage, where a machine learning (ML) system returns the outputs we want but for the wrong reasons (Crawford 2021: 4). For example, a classiÞer trained to identify which images from a CT scanner are likely to show the body of a patient with cancer can achieve high precision by simply classifying all images with a higher resolution and image quality as likely to indicate cancer. This works because patients only get scanned in the more expensive machines when their doctors have other reasons to believe that their chance of having cancer is particularly high. The ML classiÞer seems to perform well, but is actually generating no new information at all nor picking up on how a tumor looks on a CT scan. With the dramatic recent rise of ML in science, data leakage has become a widespread problem (Kapoor and Narayanan 2023). Both in the case of ML and in animal psychology, our scientiÞc interpretation of a system can be gravely mistaken if we fail to investigate carefully which parts of the information available to a system or subject actually guide its behavior. We often fail to do so because we project our own perceptions and evaluations of a task or situation onto those systems and subjects which are very di.erent from us. This insight, and a dissatisfaction with the anthropomorphic animal psychology of the turn of the century, drove Jakob von UexkŸll to develop a new conception of biological research centered around the term Umwelt. An Umwelt is the world experienced by an animal according to its physiology and its behavior in its habitat, and di.erent animals have di.erent Umwelten. This concept of Umwelt and its reception in philosophy and cognitive science is the topic of this dissertation. 

1.2 Jakob von UexkŸllÕs concept of Umwelt 
Jakob von UexkŸll (1864-1944) was a German biologist born in Estonia who began his career studying the physiology of marine animals and moved on to develop a comprehensive vision for a new kind of biology that would avoid two crucial mistakes UexkŸll attributed to his colleagues, many of whom: 
1. 
treated animals as complex machines. Instead, UexkŸll emphasized that they are living subjects and each experience a world of their own. 

2. 
used anthropomorphic terminology to describe the psychology of animals. Instead, UexkŸll thought that scientists should restrict themselves to what is externally observable about the behavior, environment, and physiology of an animal. 


UexkŸllÕs empirical and conceptual work had a signiÞcant inßuence on the development of ethology, his notion of a Ôfunctional circleÕ anticipated the feedback loops of cybernetics, but the biggest part of his inßuence on the history of thought is the concept of Umwelt. Philosophers in Germany and France eagerly picked up this notion and adapted it for their own purposes, especially in phenomenology and philosophical anthropology, and today the term Umwelt is used in a wide range of Þelds, from biological studies about the Umwelten of dolphins (Kremers 2013) to theatre studies (Beloborodova & Little 2022), neuroscience (Schiller et al. 2023), user experience design (Lagerstedt & Kolbeinsson 2021), and robotics (Ay & Lšhr 2015). Within the philosophy of cognitive science, Umwelt has long been present in footnotes or short references and recently the concept has taken on a more central role in debates within embodied cognitive science (see e.g. Brooks 1986, Clark 1997, Dennett 2015, Baggs and Chemero 2018, and Feiten 2020). 
In this dissertation, I argue that UexkŸll used the term Umwelt in two distinct senses which belong to di.erent perspectives and methodologies and are not generally interchangeable. Investigating the Umwelt of an animal in scientiÞc terms from the perspective of an external observer, as done e.g. in ethology, concerns what I call the e-Umwelt of an animal. Investigating the Umwelt that a subject itself experiences from the Þrst-person perspective, as done e.g. in phenomenology, concerns what I call the p-Umwelt of the subject. Distinguishing between these two senses of Umwelt is important because it allows us to reevaluate UexkŸllÕs reception both in French and German philosophy of the early and mid-20th century, and more recently in the philosophy of cognitive science. The same conceptual logic which I identify in UexkŸllÕs thought as the origin of the two di.erent senses of Umwelt also results in the view that each human being inhabits a p-Umwelt which is self-contained and does not intersect with the p-Umwelten of other subjects. An emphatic opposition to this claim is the strongest unifying feature among a large group of otherwise heterogeneous thinkers who all valued UexkŸllÕs concept of Umwelt but rejected the idea that each human lives in their own, private Umwelt. Making the distinction between e-Umwelt and p-Umwelt allows me to show that the most prominent arguments that have been developed against the idea of individual, closed human Umwelten fail to establish that UexkŸll is wrong about this because they equivocate between the two senses of Umwelt. Additionally, the distinction between e-Umwelt and p-Umwelt illuminates the gap between an external perspective on a subject and the experience of the subject itself, which can help us conceptualize the relationships between di.erent methodologies, such as cognitive science and phenomenology. Both perspectives are valuable and allow speciÞc kinds of inquiry, but they are not interchangeable and there is no guarantee that concepts or results from one perspective are translatable into the terms and methodological constraints of the other. When a technical term such as Umwelt is used in both perspectives, it is crucial to distinguish between the two uses and investigate their relationship, which is what this dissertation does. 
It should be noted that UexkŸll himself did not distinguish between these two senses of Umwelt; I derive the justiÞcation for my claim that the term is used in two di.erent senses from a careful reading of the most relevant passages in UexkŸllÕs major works. UexkŸll himself might well have disagreed with my claim, since his goal beyond theoretical biology was to develop a holistic Ôbiological worldviewÕ [Weltanschauung] inspired by organicist and romantic thought, and a single concept of Umwelt seems more naturally in tune with this project than an ambivalent term which refers to two di.erent concepts. In this hypothetical scenario, I would claim that UexkŸll himself is wrong about how he uses the term Umwelt. However, my analysis of UexkŸllÕs writings shows that the two senses of Umwelt together form a coherent conceptual system, which I believe best describes the ways in which subjective experience Þts inÑor fails to Þt inÑwith natural scientiÞc investigations of minds. 

1.3 Focus and exclusions 
In terms of the thinkers whose work I discuss, and the methods used, this analysis draws mostly on history and philosophy of science, the philosophy of cognitive science, and some continental philosophy (mostly phenomenology but also other French and German 20th century philosophy). In any research project, choices have to be made about how to draw the boundaries of discussion. Since the general subject matter of this project is of interest to a variety of di.erent disciplines, many more interesting connections and comparisons could have been included in principle, but not in practice. Two notable exclusions deserving a short explanation are biosemiotics and (analytic) philosophy of mind. 
Biosemiotics is a Þeld that claims UexkŸll as one of its founders and one of eight ÒTheses on BiosemioticsÓ outlined by leading thinkers in the Þeld focuses on Umwelt (Kull et al. 2009). Drawing amongst others on the pragmatist philosopher Charles Sanders Peirce, biosemiotics postulates that the notion of semiosis should be central to any biological theory. There is a rich literature on UexkŸllÕs thought in biosemiotics, so it might seem like an oversight not to discuss this body of work in a dissertation on UexkŸll. However, because of its emphasis on signs and its particular disciplinary position as a self-standing project with little connection to other Þelds, including the subÞelds of philosophy which I focus on, the literature in biosemiotics does not bear on the questions discussed here as strongly as one might have thought. Occasionally, biosemiotics is discussed in relation to embodied cognition (see e.g. Heras-Escribano and De Jesus 2018), but these discussions are not directly connected to the debates I address in this dissertation. 
Since UexkŸll conceived Umwelt as a method for the study of animal minds that was meant to supplant the anthropomorphic animal psychology of his colleagues, the Þeld of philosophy of mind seems prima facie relevant to my discussion. There are obvious points of connection between UexkŸllÕs (2010[1934]) account of the Umwelt of e.g. a tick and the questions raised in Thomas NagelÕs (1974) paper ÒWhat Is It Like to Be a Bat?Ó. This comparison may well be worth conducting in a separate text. The fate of subjective experience in analytic philosophy of mind in the last half-century has unfortunately produced a kind of conceptual gridlock that limits its value for the present analysis. The available positions are not just well-entrenched and insulated from the arguments of their opponents, but the support for each view is also typically framed in terms that are idiosyncratic to analytic philosophy of mind and do not carry over well either to a discussion of UexkŸll or to most of the other thinkers discussed in this project (with notable exceptions in chapter 5). In discussing subjective experience, I focus on phenomenology and related approaches, which might be considered part of philosophy of mind in a broad sense, but treat the topic very di.erently from the debates about ÔqualiaÕ that developed in the broadly analytic-anglophone style. I also do not develop a detailed and self-standing argument for the claim that there is such a thing as private subjective experience. The existing literature suggests that no side is capable of convincing the other: To some, private subjective experience is given to us so directly and obviously that it makes no sense to derive it from any other source, empirical or rational (see e.g. Strawson 2018). To others, the very concept of subjective experience (often in the form of ÔqualiaÕ) is unclear and ill-deÞned and should just be dropped from our philosophical vocabulary (see e.g. Dennett 1988). Even though I belong to the former camp, for the purposes of intervening in debates about the interpretation of UexkŸllÕs texts and their reception, developing my own account of the metaphysics of subjective experience and trying to convince others that this is the right one seems ine.icient. Instead, I focus on trying to make my reading of UexkŸll and my own views (to the degree that they intersect) as intelligible as possible and to outline the trade-o.s involved in holding di.erent possible views on subjective experience (mostly in chapters 4 and 6). 
The reasons for including those particular thinkers I discuss are both systematic and historical, following my primary interest in the use of Umwelt in present-day embodied cognition. Since a central question in these debates is whether the Umwelten of humans are open or closed, prior philosophical reception of UexkŸllÕs work that addresses this question is relevant. Simultaneously, some of the French and German philosophers who most prominently took up the concept of Umwelt, but disagreed with UexkŸll about the Umwelten of humans, are Maurice Merleau-Ponty and Martin Heidegger, both of whom played important roles in inspiring the embodied approach to cognition. Phenomenology in particular will be central to my discussion of embodied subjective experience in chapter 6. Tracing the concept of Umwelt from UexkŸllÕs own writings, through French and German philosophy, into current debates in embodied cognitive science, is thus an organic choice both in terms of the philosophical question I focus on and because they form a historical lineage of inßuence and reception. 

1.4 Roadmap for a foray into the worlds of scientists and philosophers 
Overall, this is what my project does: I show that UexkŸll employed the term Umwelt in two di.erent senses without making this di.erence explicit. The e-Umwelt describes the Umwelt of an animal from the perspective of an external scientiÞc observer and the p-Umwelt concerns the subjective experience of the animal itself. This distinction follows from UexkŸllÕs belief that all organisms have subjective experience, but that a scientist never has direct access to the subjective experience of the organism they are studying. Consider for example how psychologists rely on physiological measurements and verbal reports as proxies for the subjective experience of their experimental subjects. Neither a measurement of the levels of blood oxygenation in someoneÕs brain nor their verbal report of seeing a red triangle is the same thing as their phenomenal experience of seeing a red triangle. Both give us only indirect information about their experience, and we rely on them because we do not have direct access to their phenomenal experience in the way they themselves do. This view that subjective experience is fundamentally private can also be stated as the claim that all p-Umwelten are closed. The distinction allows for the most coherent reading of UexkŸllÕs main works, which would su.er from internal contradictions if Umwelt were always used in one single sense, and resolves two other prominent problems of interpretation in the literature. Importantly, this distinction also allows us to assess the reception of the term Umwelt in a systematic way. UexkŸllÕs claim that each individual human lives in a closed Umwelt has found almost unanimous disagreement in his philosophical reception. Distinguishing between the two senses of Umwelt allows us to see that most arguments advanced by French and German philosophers in the 20th century, as well as more recently by philosophers of embodied cognition, only show that e-Umwelten are open. Whether e-Umwelten are treated as open or closed is a methodological choice which is made in accordance with speciÞc scientiÞc goals. In contrast, the question of whether p-Umwelten are open or closed has important philosophical consequences, since it boils down whether two or more subjects can ever share the same token (phenomenal) experience and thus concerns the metaphysical nature of subjective experience. I point out problems with attempts to support the view that p-Umwelten are open by appeals to our personal experience of social encounters or phenomenological analyses of intersubjectivity and sketch an alternative account of the kinds of experiences of intersubjectivity which we have as occurring within separate and closed p-Umwelten. One advantage of the reading of UexkŸll I o.er is that this account of two senses of Umwelt allows us to take seriously that each subject has their own phenomenal experience while also respecting the epistemic constraints on any scientiÞc investigation of these subjects. 
Chapter 2 lays the groundwork for an interpretation of UexkŸllÕs concept of Umwelt. This involves primarily an outline of UexkŸllÕs life and works, with short summaries of major ideas as they are developed in his most important monographs. I chart his development from a university student of zoology into a researcher conducting his own physiological studies of marine animals and growing increasingly skeptical of a mechanistic view of organisms in the last decade of the 19th century. In the 20th century, I follow UexkŸllÕs bumpy career trajectory that eventually results in the creation of the Institut fŸr Umweltforschung [Institute for Umwelt Research] under UexkŸllÕs leadership in Hamburg. Two main components that develop in UexkŸllÕs thought are an account of animal subjects and the conditions of possibility of their experience, inspired by Immanuel Kant but transposed into a physiological account, and a holistic view of nature as structured by harmonies and melodies, inspired by Johann Wolfgang von GoetheÕs romantic thought. Against recent claims to the contrary in the secondary literature, I argue that these di.erent parts of UexkŸllÕs thought can be logically and conceptually separated from each other, as is also illustrated by copious research in biology that makes use of Umwelt without any reference to UexkŸllÕs holistic and organicist views of nature. This establishes the possibility of my own study, which likewise deals with Umwelt but excludes all other parts of UexkŸllÕs thought. 
In chapter 3, I present my view that UexkŸll uses Umwelt in two distinct senses and argue why this is the best interpretation of his writings. UexkŸll develops strict methodological principles for biologists which limit them to a description of the features and behaviors of an animal in its environment that they can observe as an external observer. This yields an ethological description of Umwelt, or e-Umwelt. Additionally, UexkŸll also invites us to imagine what it would be like to be not a human but a di.erent kind of animal subject. This description of an Umwelt takes on the Þrst-person perspective of a subject on its Umwelt as it is given to it in experience, yielding a phenomenal Umwelt or p-Umwelt. Distinguishing between these two senses of Umwelt can dispel the contradiction that arises when UexkŸll simultaneously describes Umwelt both as a something that biologists gain knowledge of through external observation of an animal and as something that is fundamentally private and accessible only to that particular animal whose Umwelt it is. For the biologist, only the e-Umwelt is knowable, while the p-Umwelt of the subject is fundamentally private. Additionally, this distinction also resolves existing disagreements in the literature about whether an Umwelt is selected or constructed and whether it belongs to a species or to an individual. At the same time, the fact that this distinction has not been drawn until now explains why the disagreements arose in the Þrst place. 
In chapter 4, I focus on the question of whether Umwelten are open or closed. Even though this has been the main point on which philosophers who valued UexkŸllÕs thought have disagreed with him, no systematic discussion of what these disagreements entail has yet been conducted. Such a discussion is important because the terminology of open or closed Umwelten is still central to debates about UexkŸll in embodied cognitive science. I Þrst give an overview of this issue by surveying some of the di.erent ways in which philosophers have disagreed with UexkŸllÕs view that individual humans each live in a closed Umwelt and showing some shortcomings of how these arguments are treated in existing secondary literature. Next, I use the di.erence between e-Umwelt and p-Umwelt to create a more Þne-grained distinction between di.erent claims that have been made about the openness or closure of Umwelt. This yields Þve di.erent kinds of claims, for each of which I specify the kind of evidence or argument that would be required to support it. It turns out that there is a strong case for treating e-Umwelten as open for methodological reasons, but that the question of whether p-Umwelten are open or closed is a question about the metaphysics of subjective experience and thus requires more speciÞc philosophical arguments. 
Chapter 5 discusses how the term Umwelt has been used in the philosophy of cognitive science. First, I show that Andy Clark and Daniel Dennett use the term Umwelt in a sense that is agnostic as to whether the system that is said to have an Umwelt has subjective experience or not. I argue that this is likely to distort the general perception of UexkŸllÕs thought and his conception of Umwelt. Next, I argue against Ed Baggs and Anthony Chemero that the term Umwelt cannot bridge the gap between an external perspective on an organism (as adopted by ecological psychology) and the subjective experience of the organism itself (as emphasized by phenomenology and enactivism). I show how the distinction between e-Umwelt and p-Umwelt dispels the false impression that these two perspectives can be merge in this way. Lastly, I criticize a view that adopts UexkŸllÕs musical metaphors of nature as grand symphony Þlled with melodies and harmonies between all organisms for ecological psychology but argues against the concept of Umwelt. I argue that the arguments against Umwelt can be countered by distinguishing between e-Umwelt and p-Umwelt and suggest reasons against adopting UexkŸllÕs musical metaphors of nature as a harmonious whole. 
In chapter 6, I pursue the question of whether humans share subjective experience in a strong sense, by which I mean that they sometimes undergo numerically, rather than merely qualitatively, identical experiences. If it could be demonstrated that strong sharing occurs, this would mean that human p-Umwelten are open. I discuss Thomas Fuchs and Hanne de JaegherÕs enactive account of intersubjectivity as one candidate view that seems to advocate for strong sharing. I argue that we cannot know from our own experience whether strong sharing occurs even when it feels to us as if it does, and that accounts without strong sharing are compatible with canonical views of intersubjectivity in the history of phenomenology. SpeciÞcally, I show that even though characterizations in the secondary literature sometimes suggest the contrary, HusserlÕs phenomenological account of intersubjectivity does not involve strong sharing. I Þnish with a brief sketch of how social encounters that feel as if they involve strong sharing can be accounted for without assuming that strong sharing really occurs. My claim is not that Fuchs and De Jaegher fail to describe intersubjectivity in terms of strong sharing, but rather that the same phenomena can be accounted for without strong sharing, and that since we have no conclusive way of knowing whether strong sharing really occurs, we should not posit that it does. 
Chapter 7 concludes this dissertation with a brief summary of what has been achieved and suggests three directions for further research that builds on this work. First, I hypothesize that there are two senses of ÔembodimentÕ in use within the philosophy of cognitive science, an ÔexternalÕ sense derived from robotics and an ÔinternalÕ sense derived from phenomenology, and that their di.erence corresponds to the di.erence between e-Umwelt and p-Umwelt. Second, I sketch how the distinction between e-Umwelt and p-Umwelt might allow us to reassess the reactions to UexkŸllÕs thought in French and Germany philosophy in more detail. Lastly, I argue that the analysis in chapter 6 can be used to specify epistemic limits for the kinds of questions that can be answered by a strictly phenomenological investigation and that these constraints for the possibility of a Ôphenomenology from the outsideÕ signiÞcantly limit the scope of what a Ôphenomenology of artiÞcial intelligenceÕ could be. 
Chapter 2: UexkŸllÕs Ideas 
2.1 Reading UexkŸll 
The aim of my project as a whole is to identify and distinguish the two main ways in which UexkŸll uses the term Umwelt and apply this distinction to current debates in the philosophy of embodied cognitive science. For this distinction to be relevant and applicable to ongoing debates, it has to be partially independent both from the historical context in which UexkŸll wrote and from other parts of UexkŸllÕs thought. By this I mean that the two senses of Umwelt I identify have to be intelligible in current conversations in which neither the historical context nor the full breadth of UexkŸllÕs thought is known to most participants. Most of the scholars working today who draw on UexkŸllÕs concept of Umwelt in a wide range of disciplines including theatre studies (Beloborodova & Little 2022), neuroscience (Schiller et al. 2023), user experience design (Lagerstedt & Kolbeinsson 2021), and robotics (Ay & Lšhr 2015), likewise treat Umwelt as an isolated concept that functions on its own. This method stands in contrast to a view recently advanced by Gottfried Schnšdl and Florian Sprenger (2021), who argue that UexkŸllÕs thought, including his biological research, his philosophical borrowings from Kant and Goethe, and his reactionary political vision of a totalitarian state modeled on the concept of an organism, forms one coherent whole and that no part of it, explicitly not the concept of Umwelt, can be taken from it without the danger of importing totalitarian thinking along with it. If their claim were true, this would be disastrous not just for my own project, but also for the current literature drawing on the concept of Umwelt across a wide range of disciplines. 
In the following section I give an overview of UexkŸllÕs broader oeuvre and his historical context from which I will isolate the two central senses in which Umwelt is used. The next section will summarize Schnšdl and SprengerÕs claim and argue that it lacks both argumentative and evidential support. Contrary to their position, UexkŸllÕs thought is not a monolithic whole permeated by a single conceptual logic, but a historically contingent set of texts that interweaves a variety of intellectual inßuences. By giving an overview of the main threads, I set the stage for the next chapter, in which I disentangle UexkŸllÕs thought and identify two distinct senses in which he uses the term Umwelt. 

2.2 UexkŸllÕs life and work 
UexkŸllÕs published work contains a small number of central ideas that are repeated in di.erent works over multiple decades. Just like his own vision of nature as one single overarching whole that is organized according to an inner principle, his thought may sometimes appear as if a single idea or intellectual conviction is continuously unfolding and blossoming into individual concepts and views. However, UexkŸllÕs intellectual biography reveals a number of di.erent inßuences that he strove to integrate into his thought in various ways and at di.erent points in time. The development of his thought is not so much the necessary trajectory of a single idea logically pursued, but a historically contingent process in which a set of biological ideas grew over time into a philosophy of nature and an organicist worldview shaped by both political and personal events. This chapter gives an overview of this development that is not meant to be exhaustive but attempts to provide enough context to ground a historically informed analysis of his key concept of Umwelt in the next chapter. 
UexkŸll was a proliÞc writer, publishing Òmore than a dozen books and well over twelve dozen papersÓ over the course of his lifetime (Winthrop-Young 2010: 209). This biographical sketch will not mention all of UexkŸllÕs publications, nor discuss their content in comprehensive detail. Instead, I will give brief topical summaries of UexkŸllÕs most important ideas as they appear in major works, and merely mention the publication of some minor works not commonly discussed, to provide a relatively well-rounded impression of the kind of writing UexkŸll published in book form. Beyond his monographs, UexkŸll authored many academic papers and newspaper articles, but most of that work goes beyond the scope of this investigation. UexkŸll repeated the same ideas many times over, and the following presentation is the result of a trade-o. between the need for a concise overview of UexkŸllÕs thought and the wealth of material published over the course of his career. 
Jakob von UexkŸll was born on September 8th of 1864 in Keblas, in present-day Estonia, Òthe Þfth child of an aristocratic German Baltic familyÓ (Harrington 1996: 35, see Brentari 2015: 22 and Schnšdl & Sprenger 2021: 235). His ancestors had arrived in the region along with Òthe Þrst arrivals of German knights in the Baltic landsÓ (Brentari 2015: 21). He grew up Þrst on the family estate, then attended school in Coburg and Reval. During his school years, he Òread KantÕs Critique of Pure Reason, from which he drew strong intellectual stimulationÓ (Brentari 2015: 22). In 1884, he enrolled in the university at Dorpat (now Tartu) and started studying zoology. Although he was convinced as a child that Òthere are miracles in natureÓ, by the time he started his university studies, UexkŸll had already Òbecome a convinced determinist and materialist and had turned his back on ChristianityÓ (Harrington 1996: 38). Already in his Þrst year at university, he Òset o. for the Dalmatian island of Lesina (now Hvar) with Alexander Braun Ð his zoology teacher, who held a vitalist positionÓ, beginning his decades-long work in the direct empirical observation of marine animals that would shape his scientiÞc career (Brentari 2015: 23). From the 1890s onwards, he would traverse this trajectory back in the opposite direction. Studying zoology in Dorpat, he Þrst became disillusioned with Darwinism and switched his research interests towards physiology (Harrington 1996: 38-39). UexkŸllÕs negative reception of Darwinism may have been inßuenced by Karl von Baer, then a widely renowned biologist. ÒAccording to von Baer, the weakness of the Darwinian theory of evolution consists in its being focused solely on antecedent mechanical causes and on random variations, and that it actually ignores the teleological character of every organic processÓ (Brentari 2015: 24). 
In 1888 UexkŸll moved to Heidelberg in Germany, where he studied physiology with Wilhelm KŸhne. He Ògraduated in 1890 with a thesis on the parietal organ in the frogÓ (Brentari 2015: 26). In 1890, he also started doing research at the zoological station in Naples, where he met the embryologist Hans Driesch in 1891 (Harrington 1996: 39). While UexkŸll was researching the physiology of Eledone moschata, Driesch studied the development of sea urchins (Mildenberger & Herrmann 2014a: 5, Mildenberger & Herrmann 2014b: 274Ð276). Out of this research came DrieschÕs most famous discovery that the embryo of a sea urchin will develop into two separate, complete adult organisms if cut in half early enough in its development. UexkŸll took this to be a conclusive demonstration that organisms are not mere machines (von UexkŸll 2010: 194). DrieschÕs discovery seems to have played a big role in driving the development of UexkŸllÕs views away from the materialism of his youth towards the vitalism-friendly position he would occupy for the coming decades. In a trio with Rudolf Magnus, another physiologist, UexkŸll and Driesch Òworked together aggressively at scientiÞc meetings to undermine mechanistic principles in the life sciencesÓ (Harrington 1996: 39). 
UexkŸll studied marine invertebrates Òadapting methods of preparation and stimulation developed by KŸhne for frogsÓ, but also Òwent to Paris to learn the techniques of serial cinematography developed by the French physiologist Etienne Jules Marey for the purposes of studying body movementÓ and applied them to Òwhole-organism studies of locomotion in both the seaworm Sipunculus and the sea urchinÓ (Harrington 1996: 39). Impressed by the ability of animals without a central nervous systemÑmere Òrepublics of reßexesÓ, as UexkŸll called themÑto achieve coordinated movement, he developed the concept of a ÒBauplan, or ÔblueprintÕ to express his early impression of preestablished teleological coordination in marine animalsÓ (Harrington 1996: 39, 40). Harrington describes this as the ÒÞrst step in [É] a long journey of metaphor transmutation and expansionÓ leading up to Bauplan becoming Òthe cornerstone of a comprehensive world view operating at once as a biological, political, and spiritual principleÓ (40). Despite UexkŸllÕs anti-mechanistic theoretical views, his own method for investigating and explaining physiological phenomena was basically mechanistic. ÒThis coexistence of a mechanistically oriented research practice and a teleological-vitalist philosophy of life was a characteristic of the UexkŸllian approachÓ (Brentari 2015: 27). 
In Heidelberg, UexkŸll studied Kant Òsystematically with a small reading group that included [É] future historian Alfred von Domaszewski, and his physiologist friend Rudolf MagnusÓ (Harrington 1996: 41). UexkŸll developed a psychologized reading of KantÕs philosophy, where the structures that constitute the condition of possibility of our experience are not Òof a transcendent or logical natureÓ as Kant intended, but Òconstraints imposed by an organismÕs sensory organs and biological constitutionÓ (41). These ideas would be expressed in UexkŸllÕs publications for decades to come, but they already played a part in the development of his thought at this early stage. Recalling his time in Heidelberg, UexkŸll describes an experience in the forest: 
ÒThis is not a beech tree, but rather my beech tree, something that I, with my sensations, have constructed in all its details. Everything that I see, hear, smell, or feel are not qualities that exclusively belong to the beech, but rather are characteristics of my sense organs that I project outside of myselfÓ (unpublished autobiographical notes, quoted in Harrington 1996:  41). 
We see how UexkŸll already at this early stage adopts key features of KantÕs account of subjectivity into a form of constructivism while also deviating from KantÕs system in such a way that both the nature of the conditions of our experience and the way in which we can know them are changed signiÞcantly. Instead of categories known a priori, the physiological features that enable and shape our experiences of the world are known and knowable through empirical science. The idea that the objects we encounter in our experience and their features are not independently existing real entities, but instead the results of a complex physiological process which gives rise to phenomenal consciousness and structures it into three dimensional space and a temporal sequence led UexkŸll to conclude that each living organism, since they each have their own physiology, must live in a private universe of experiential objects, constructed by its own biological activity. References to KantÕs philosophy in the rest of this chapter and the dissertation as a whole should always be read in light of UexkŸllÕs own interpretation of them, which is not that of a professional philosopher, but a biologist who enthusiastically picks up philosophical ideas for his own thought. 
From 1899 to 1900, UexkŸll studied in Dar es Salam, present-day Tanzania (Schnšdl & Sprenger 2021: 235). In 1899, UexkŸll published a paper co-authored with Albrecht Bethe and Theodor Beer attacking Òthe use of anthropomorphic ÔsubjectiveÕ terminology in animal sensory physiologyÓ (Harrington 1996: 42; Beer, Bethe & UexkŸll 1899). For UexkŸll this view followed from his conviction that animals can only be studied from the outside, but their subjective experience is in principle inaccessible to other subjects and thus closed o. from scientiÞc study. The paper, however, Òwas to have a broad impact on the rise of behaviorism in the United States and of Pavlovian reßexology in RussiaÓ, which led the Òantimechanistic UexkŸllÓ to distance himself from the early paper later in life (Harrington 1996: 42). In contrast to this inßuence on psychology, the paper had largely Òbeen ignored in physiological and biological discussionsÓ (Mildenberger 2006: 175). 
Following KŸhneÕs death in 1902, UexkŸll had lost access to the laboratory in Heidelberg, and then also to the Zoological Station in Naples (Brentari 2015: 28). Although he was able to Þnance some research trips himselfÑBrentari (2015: 28) lists Beaulieu, Rosco., Berck sur-Mer and BiarritzÑ UexkŸll increasingly turned from empirical observation towards theoretical reßection, publishing the short monograph Im Kampfe um die Tierseele [Battle over the Animal Soul] in 1902. This book describes the Òbattle to the endÓ between the two Þelds of comparative psychology and physiology (von UexkŸll 1902: 3). While comparative psychologists assumed that the nervous system of other animals must produce sensations just as it does in humans, physiologists limited themselves strictly to studying the observable e.ects of observable processes. UexkŸll describes the justiÞcation o.ered by comparative psychologists for believing in the existence of an unobservable Òanimal soulÓ through a comparison: If we found the skeleton of an extinct species of crab, we would be justiÞed in thinking that its legs were for walking, even though it would be impossible to make any empirical observations of this stipulated activity or to conÞrm it experimentally (von UexkŸll 1902: 3). In contrast to the psychological view, physiologists understood the nervous system as a complex network in which di.erent waves of excitation get received from sensory organs and transmitted to the muscles. This led to the disappearance of the Òsensations, memory, and thoughts of the animalsÓ from science, replaced by the Òiron chain of objective changesÓ (von UexkŸll 1902: 4). Based on this view, physiology declared comparative psychology to be not a natural science but mere superstition (ibid.). The stand-o. between physiologists and comparative psychologists comes down to the question: ÒWhat is the relationship between our sensations and the processes in our brain?Ó (von UexkŸll 1902: 5). 
UexkŸll strives to elucidate this epistemological question by appealing to KantÕs philosophy. He Þrst emphasizes that Òeverything we know is known to us only because it is the content of our consciousnessÓ (von UexkŸll 1902: 6). Hence, Òthe world exists for each individual only in that form in which it is presented by oneÕs own consciousnessÓ (ibid.). UexkŸll declares KantÕs demonstration of the fundamental status of time and space for our experience to be the Òfoundation of all psychological research for all timeÓ (von UexkŸll 1902: 7). UexkŸll sees KantÕs account of the process of apperception as the basis for our understanding of how humans and other animals generally perceive their environments. He combines KantÕs account of the role that concepts play in apperception with his own work on sensory physiology and compares this perspective to Newton, Mach, Fechner, and Helmholtz (17). Returning to the problem faced by comparative psychologists, UexkŸll concludes that Òknowledge of anotherÕs soul is permanently closed o. to us, since there is no direct tra.ic from soul to soulÓ (von UexkŸll 1902: 19). UexkŸll emphasizes that he is not claiming that animals have no psyche, just that it is not possible to have any experience that could answer this question (ibid.). 
From this limitation, UexkŸll moves on to sketch the task of biology. He points out that too little attention has been paid to the ÒmilieuÓ in which an animal lives. Only by properly taking into account the environment in which the animal pursues nutrition and reproduction can we understand how the physiology of an animal contributes to it achieving its goals (von UexkŸll 1920: 21). In discussing how the di.erences in sensory apparatus and nervous system correspond to di.erent milieus of various species, UexkŸll is here anticipating the idea he will later discuss under the name Umwelt, but without using that term (von UexkŸll 1902: 23). 
In 1903 UexkŸll married Gudrun von Schwerin and in 1905 he published Leitfaden in das Studium der experimentellen Biologie der Wassertiere [Guideline for the experimental study of marine animals] (see Schnšdl & Sprenger 2021: 235). UexkŸllÕs chances for an academic career at this time were not good, since he was Òknown as a theorist of biology with a vitalist and anti-Darwinian credo, as well as a staunch supporter of the applicability of the Kantian transcendental philosophy in biologyÓ and the intellectual climate at the institutions did not favor his views (Brenati 2015: 29). In 1905, the couple moved to Heidelberg. Also in 1905, UexkŸll met the poet Rainer Maria Rilke Òon the estate of Luise von Schwerin, UexkŸllÕs mother-in-lawÓ, and the two men Òwent for long walksÓ and Òtogether studied KantÕs Critique of Pure ReasonÓ (Winthrop-Young 2010: 230). In 1907 UexkŸll received an honorary doctorate in medicine from the University of Heidelberg for his experiments on the Òprinciples underlying muscular and nervous processes in invertebrate marine animalsÓ (Harrington 1996: 39). 
From 1907 on, UexkŸll used the term Umwelt to describe the worlds of di.erent animals as they perceive them. Until then, ÒUmweltÓ had been used to refer Òto the milieu or environment and was used primarily in sociological analysesÓ (Harrington 1996: 41). Within biology, the surroundings of animals had been referred to as ÒenvironmentsÓ or ÒmilieusÓ. In French biological writing, Òthe term ÔmilieuÕ (medium) as the counterpart of ÔorganismeÕ was an innovation of the 1830sÓ, and the term ÒenvironmentÓ was Þrst used in Òa biological context by the social thinker Harriet Martineau as her preferred translation of ComteÕs Ômilieu.ÕÓ (Pearce 2014: 15, 17; for a chronological listing of relevant examples of the terms ÒUmweltÓ, ÒmilieuÓ and ÒenvironmentÓ occurring in the literature between the 18th and 21st century, see also Toepfer 2023). The word ÒUmweltÓ had Þrst been used in German by Jens Immanuel Baggesen in his poem ÒTo NapoleonÓ, and UexkŸllÕs use of the term was a ÒscientiÞc semantic neologism, that is, an attempt to redeÞne the meaning of a widely used word in accordance with a scientiÞc theoryÓ (Winthrop-Young 2010: 215, 216). UexkŸll was unsuccessful in this attempt insofar as German speakers today understand the term in the sense of the ÒenvironmentÓ in ÒenvironmentalismÓ, but he also failed to make the meaning of his own usage as a term of art clear in a way that will become the focus of the next chapter. 
The term Umwelt Þrst takes on its central role in UexkŸllÕs writings with the publication of Umwelt und Innenwelt der Tiere in 1909. By far most of the book is taken up with descriptions of di.erent animals, their physiology, and the way they live in their habitats. From the unicellular Paramecium and Amoeba terricola, over Aneonia sulcata, medusae, various sea urchins, serpent stars, Sipunculus, earthworms, leeches, scallops, Carcinus maenas, cephalopods, to dragonßies, UexkŸll presents a dazzling array of animals, with a clear focus on the sea creatures his own empirical research dealt with. In addition to the chapters on speciÞc animals, the book also contains several theoretical chapters, starting with Òthe protoplasm problemÓ, in which UexkŸll argues that animals cannot be understood as machines. In particular, the powers of morphogenesis and regeneration seem to him to be ÒsupermachinicÓ and he emphasizes that they follow some rule or plan which we do not have knowledge of, citing DrieschÕs adoption of the Aristotelian term ÒentelechyÓ to explain the direction of morphogenesis towards an adult state and von BaerÕs references to Ògoal directednessÓ (von UexkŸll 2014[1921]: 10). The other theoretical chapters deal with the Òreßex arcÓ, the ÒUmweltÓ, the ÒGegenwelt [counter world]Ó, and the ÒobserverÓ. The latter of these contains a clear and concise statement of some of UexkŸllÕs core methodological commitments. He states our general inability to gain access to the conscious experience of any living animal but ourselves and highlights the importance of this fact for the role of the researcher as a strictly external observer of biological processes (ibid. 215). UexkŸll ends the book with a list of 21 foundational rules for biologists, some of which give a very explicit account of the epistemic status of di.erent Umwelten and of the methodological consequences that follow: 
Ò1. Every creature constitutes the center of its Umwelt, which it encounters as an 
autonomous subject [...]. 
3. In the Umwelt of each animal, there exist only things which belong exclusively to this animal. [É] 
14. 
The observer can only perceive the features acting on the animal as traits of his own world of appearances. The sensations of the animal remain forever hidden to him. 

15. 
Every animal carries its Umwelt around with it for all its life like an impenetrable shell. 

16. 
The same is true of the observerÕs world of appearances, which closes him o. completely from the universe, since it constitutes his Umwelt. [É] 


19. The world of appearances of each human being likewise resembles a hard shell, which constantly encloses them from birth until death.Ó (von UexkŸll 2014[1921]: 236.237, my translation) 
A broader reception of Umwelt und Innenwelt der Tiere only started with its second edition in 1921 (Hermann & Mildenberger 2014: 7). Apart from changes in the introduction and the Þnal chapter ÒThe ObserverÓ, the second edition importantly substitutes a new chapter called ÒThe Functional CircleÓ for the former ÒThe ReßexÓ (Mildenberger & Hermann 2014: 7). In less than Þve pages, UexkŸll gives an exposition of his notion of the functional circle, a short account of which follows below in the discussion of the book Theoretische Biologie, in which UexkŸll had introduced the term in 1920. 
In 1913, F. Bruckmann A.G. in Munich published Bausteine zu einer biologischen Weltanschauung [Building blocks for a biological worldview], a collection of UexkŸllÕs essays. The book was dedicated to the racist, antisemitic philosopher Houston Stewart Chamberlain, and collects 18 essays organized into four sections, titled ÔThe New ProblemsÕ, ÔThe New StandpointÕ, ÔThe New WorldviewÕ, and ÔSpecial QuestionsÕ. UexkŸll situates his own views as explicitly and aggressively anti-Darwinian, opening his Þrst essay like this: 

Fig. 1: Opening sentences of Bausteine zu einer biologischen Weltanschauung, p. 17. 
or: 
We are standing on the eve of a scientiÞc bankruptcy, the consequences of which are 
yet inestimable. Darwinism is to be stricken from the range of scientiÞc theories. (von 
UexkŸll 1913: 17, translations from Bausteine are all my own). 
UexkŸll argues that Darwinism does not need to be disproven anymore, because it has collapsed in on itself. Even though the broader public will continue to believe the dogmas of this Òteaching that has grown into a kind of religionÓ for years to come, UexkŸll claims that experimental biologists have left Darwinism behind for several reasons (17). The Þrst reason is DarwinismÕs claim that Ònew species originate from old ones through continuous changeÓ, also known as the doctrine ÒNatura non facit saltusÓ (17). After negatively discussing some work that suggests gradual species change, UexkŸll appeals to the work of Òde VriesÓ as Òreliable experimentsÓ which have Òdelivered proofÓ that Ònew species can emerge through sudden, unmediated transitionsÓ and states that Darwin himself already provided an example of this (18). He does not specify which example of DarwinÕs he is referring to, but we can assume that the other reference is to Hugo de VriesÕ work on Oenothera lamarckiana (see Nei and Nozawa 2011). De Vries conducted experimental work on the evening primrose for 13 years which provided the empirical foundation for his Òmutation theory of evolutionÓ (Nei and Nozawa 2011: 812). Nei and Nozawa argue that, although Òde VriesÕ work is now often regarded as a failed attempt to modify DarwinÕs theory of origin of speciesÓ, based on discoveries by Thomas Morgan in the 1910s and 20s, Òrecent [21st century] genomic data abundantly support [de VriesÕ] theory of origin of species by chromosomal changesÓ and he was Òright in his proposal of mutation theoryÓ (812, 813). Beyond UexkŸllÕs pugnacious rhetoric, it is worth noting that at least some of the reasons he had for rejecting the view he referred to as ÔDarwinismÕ were plausible then and are arguably still plausible. Otherwise, there is a danger of forming an overly negative picture of UexkŸll as merely a biologist who rejected Darwin and was proven wrong by posterity, which might lead to a hasty rejection of UexkŸllÕs thought in general. 
But UexkŸll quickly moves on from empirical arguments to more general di.erences in theoretical outlook. According to him, Darwin relied primarily on a comparison between selective breeding, or artiÞcial selection, and the processes that give rise to new species in nature, as well as the potential for wide variations in the appearance of many animal species (von UexkŸll 1913: 18). UexkŸll claims that DarwinÕs ÒassumptionÓ that Ònew species originate from variationÓ has turned out to be ÒerroneousÓ (19). Instead, he claims, variations within a species, both those induced through selective breeding and those due to di.erences in habitat, revert back to the stem species within a few generations when left to the forces of nature (19). 
UexkŸll contrasts the ÒDarwinianÓ and the ÒAnti-DarwinianÓ view of biological organisms, describing this opposition as a disagreement over ÒvariationÓ versus ÒmutationÓ as the source of speciation. The Darwinian proponents of variation treat an organism as a Òconglomerate of various substancesÓ whose Òstructure is merely the result of a kind of inner fermentationÓ (19). This fermentation causes Òone or another part to vary, and if all the parts of an individual have been varied, it therefore belongs to a new speciesÓ (19). In contrast, UexkŸll maintains that Òfollowers of mutationÓ see organisms as paintings, which may take on some ÒvarietyÓ through Òoccasional changes in colorationÓ, but without thereby changing the Òoverall composition of the paintingÓ (19). A central claim of the Òthe new biologyÓ maintains that the parts of every organism are Òassembled according to a Þxed planÓ, and the organism is not Òan aimlessly fermenting heap of matter that only obeys physical and chemical lawsÓ (19). Accordingly, Òevery new species is characterized by a new planÓ (20). 
UexkŸll doubts that Òselection of the most ÞttingÓ can be the main principle of species change, because he thinks that direct competition between individuals is relatively rare (20). He reverses the notion of a Òselection of the ÞttingÓ from Herbert SpencerÕs account of Ònature selecting the organisms that Þt itÓ to his own view that Òeach organism selects the nature that Þts itÓ (20). What he means by this is that individual organisms do not all inhabit Òone general chaos of material point in space, in which only physico-chemical forces are at playÓ, but instead Òevery organism, according to its design, only relates to a small part of the external worldÓ (19-20, 20). ÒEvery individual creature creates for itself via this relationship an Umwelt unique to itself, in which its life plays outÓ (20, emphasis added). Eyes and ears select only certain wavelengths out of those occurring in the physical environment. Because each animal is striving to organize a di.erent part of the external world and turn it into its Umwelt, Òdirect competitionÓ between them is the exception, rather than the rule (20). This argument is not convincing, and we will come back to what exactly is wrong with it in the next chapter. 
Another aspect of UexkŸllÕs later views that is already present in this early collection of essays is adaptation of a quasi-Kantian view of perception. He develops this view as part of his account of Umwelt, and it is deeply intertwined with his methodological views about the tasks and limits of biology. We encounter this Kantian inßuence Þrst in the essay Ò†ber das Unsichtbare in der NaturÓ (ÒOn the Invisible in NatureÓ), which opens section two of Bausteine, titled ÒThe New StandpointÓ (55). Inspired by KantÕs account of the subject, UexkŸll states that a Òspace schemaÓ and a Òtime schemaÓ combine into the Òsca.olding of objectsÓ (58). Such a schema is the Òinvisible connectorÓ that allows us to experience e.g. a chair as a chair across the di.erent circumstances and visual appearances (angles, lighting, etc.) in which we encounter it (56). UexkŸll takes these schemata to depend closely on each individualÕs past experience, which causes each human being to be encompassed by a world which is ÒadequateÓ or ÒÞttedÓ to them, their ÒUmweltÓ (58). The ÒUmweltÓ here is the world that shows up to an individual human in their subjective experience, while the schemata are the Òinvisible connectorsÓ for each kind of object (e.g. chair, tree, cloud) in this world. Further, he claims that members of particular professions have similar Umwelten that di.er systematically from the Umwelten of those in other professions, and that these di.erences show up in the vocabulary they use to draw distinctions in the world (58-59). UexkŸll highlights the importance of these quasi-Kantian meditations for biological methodology: ÒWhy is it necessary to belabor the fact that all the objects surrounding us are comprised of sensory perceptions which are ordered by spatial and temporal schemata? Ñ Because without this knowledge, there would be no comparative biologyÓ (60). While physicists and chemists only deal with the human Umwelt, once we start investigating the relationships of other animals to objects, we leave our own Umwelt and Òstep into the Umwelt of a di.erent, strange subjectÓ (60, my translation). We could Òeasily orient ourselves in this new worldÓ if we had Òknowledge of the soul of this other subjectÓ, but Òall attempts at this have failed completelyÓ (60, my translation). Furthermore, the Òtheories of parallelism or identity of brain processes and the life of the soul remain empty claims and lead, when applied to the animal soul, only to crude self-deceptionÓ (60, my translation). 
Both his inspiration by Kant and his departure from the conceptual and methodological structure of the account of subjectivity given in the Critique of Pure Reason become obvious in UexkŸllÕs ÒGedanken Ÿber die Entstehung des Raumes [Thoughts on the Origin of Space]Ó in the Þnal section of the book. UexkŸll starts out with the peculiar claim that a contemporary biologist would have to summarize KantÕs philosophy like this: ÒKant taught us that our soul is an organismÓ (284, my translation). Although a di.erent kind of Òimmaterial organismÓ, UexkŸll maintains that KantÕs account of subjectivity matches the deÞnition of an organism because both consist of three essential parts: Òstructural partsÓ, Òactive powersÓ, and Òexternal impressionsÓ (284, my translation). Our power of Òproduktive Einbildungskraft [productive imagination]Ó has the Òability to synthesize many varied parts into a new, uniÞed wholeÓ (284, my translation). With Kant, UexkŸll maintains that Òspace precedes any production of objectsÓ, but unlike Kant, UexkŸll takes it to be an active achievement of our physiology (286, my translation). The three semicircular canals in our inner ear are an organ specialized for the perception of spatial movement in the sagittal, transversal, and horizontal plane, and thus equip us with the foundation for experiencing spatiality in general. He explicitly introduces these semicircular canals as an update to the Kantian account of the three spatial dimensions. On UexkŸllÕ reading, Kant claims that the three dimensions of space are a Òstructural element of our soulÓ which exists preformed in our ÒsoulÓ without the need for any external cause. UexkŸll considers this claim to be outdated: the discovery of the role played by the semicircular canals has provided us with a physiological substitute for KantÕs idealist subjectivity (286, 287, my translation). 
In the same year that Bausteine (1913) was published, UexkŸll was Òa top contender for the directorship of the new Berlin-based Kaiser Wilhelm Institute for BiologyÓ, but the post was not o.ered to him due to concerns about his ÒÔwild and unsoundÕ theorizingÓ (Harrington 1996: 34, citing Horder and Weindling 1986: 216). 
UexkŸllÕs chances of establishing his own research laboratory were slim. Although the Kaiser.Wilhelm-Gesellschaft had rejected his request for funding a larger research project, they granted him funds which allowed him to go on research trips to ÒBeaulieu, Rapallo and BiarritzÓ between 1911 and 1914 (Brentari 2015: 29-30). With the outbreak for the First World War preventing him from doing empirical research, ÒUexku.
ll dedicated himself during the war years to expanding his theoretical concepts in new directions, launching a line of study that led him to publish a large number of writings on politics, morality and spiritualityÓ (Brentari 2015: 31). This included the 1915 Òessay Volk und Staat [People and State], in which the state is seen as a natural creation of the vital power of the peopleÓ (ibid.). UexkŸll uses his biological theory as a framework for a conservative critique of modernity and theory of the state, in which Òthe original element, the ÔcellÕ of the state, is not the individual but the family. When the family falls apart, the people and the state collapse too; and from this process emerges the typically modern phenomenon of the crowd [ÒMasseÓ]. In mass society, both socially and politically, the organic value and the purposefulness that family and people had in common with the rest of nature are missingÓ (ibid.). 
UexkŸllÕs conservative political views were likely reinforced by his experience of historical events. In 1917, UexkŸllÕs family lost all their property in Estonia when it was seized by the communist state, and the Russian State bonds comprising most of their other assets became worthless (Schnšdl & Sprenger 2021: 235, Brentari 2015: 31). The outbreak of the war found UexkŸll and his wife Gudrun von Schwerin on her property in Mecklenburg, and they only moved back to Heidelberg in 1917 (Brentari 2015: 30, 32). Here, the poet Rainer Maria Rilke, who had been a friend of UexkŸllÕs since 1904, Òasked the biologist for biology lessonsÓ (Brentari 2015: 32). From UexkŸllÕs view, the Russian Revolution had led to the Òdisappearance of the country UexkŸll had known in his youth, in which Russians, Estonians and Germans cohabitated relatively peacefullyÓ (ibid.). For economic reasons, the family moved to the village of Londorf, where he Òas well as his wifeÕs family were attacked by the Londorf community for false reasons and accused of being, as they were aristocrats, Ôparasites [and] thieves of the peopleÕs landÕ (ibid., quoting von UexkŸll 1964: 118). Through these events, ÒUexkŸll began to understand the full extent of the historical upheavals triggered by the end of the war and by the Russian RevolutionÓ and saw his views on the corrosive e.ects of overthrowing established social and political hierarchies conÞrmed (ibid.). UexkŸll thought that Òdemocracy is contrary to the natural structure of the stateÓ and Òcompared the fall of the Tsarist Empire to the dissolution of a giant amoeba in a protoplasmic decomposing massÓ (ibid.). 
In 1918, UexkŸll acquired German citizenship and in 1919 his Biologische Briefe an eine Dame [Biological letters to a lady] was published, in which he expounded his views in a more accessible language he had developed for answering questions that his wife would strategically ask him from the audience at his public talks (Schnšdl & Sprenger 2021: 235, Brentari 2015: 32). Among the theoretical output that resulted in part from his inability to conduct empirical research since the beginning of the war, by far the most signiÞcant monograph is Theoretische Biologie [Theoretical Biology], published in 1920. In this text, UexkŸll synthesized the views he had developed so far in a systematic manner and emphasized the Kantian inspiration for his account of biological subjectivity. An English translation appeared in 1926, which Brentari credits as Òresponsible for the entry of the term Umwelt in the international biology lexiconÓ (2015: 33). 
The account of how an animal gets to experience a particular world as spatial and temporal, Þlled with objects and processes that present themselves as opportunities for meaningful action, is the core concern of the Theoretische Biologie. UexkŸllÕs account of this process, informed by his empirical work on the behaviors and physiologies of marine animals but presented here as a general theory, culminates in the concept of Umwelt, as the phenomenal world experienced by an individual living subject. The sequence of chapters builds up from space and time, through sensory qualities, to objects, and Þnally to the worlds of living organisms, followed by chapters on organismic development, species, and each organismÕs conformity with its Bauplan. 
In its full sense, the Umwelt refers to the phenomenal world which an individual organism constructs for itself by turning physical stimuli into patterns of neuronal excitation which constitute signs. The Umwelt constitutes the sum total of the subjectÕs experience, but the process in which the organism constructs its own Umwelt is not conscious and is not accessible to the subject in its experience. Instead, the meaningful objects and the space in which we encounter them appear to us as objective reality. This reading captures UexkŸllÕs central concern for the animal as subject in an explicitly Kantian sense: 
ÒThe task of biology consists in expanding in two directions the results of KantÕs investigations:Ñ(1) by considering the part played by our body, and especially by our sense-organs and central nervous system, and (2) by studying the relations of other subjects (animals) to objectsÓ (von UexkŸll, 1926: 15). 
UexkŸll conceives this account in explicit reliance on KantÕs conception of the subject as Òapperceptive activityÓ, but transposed into the domain of physiological explanation (von UexkŸll 1926: 16). For the construction of subjective space, UexkŸll highlights the importance of eyes and eye muscles, movements of the head, and especially of the three semicircular canals and their correspondence to the three spatial dimensions of the sagittal, transversal, and horizontal planes (ibid. 17-19). Thus UexkŸll suggests that Òwith Kant, we make the constructive activity of the subject the very center of our considerationÓ and understands Òspace as the means whereby we construct external experienceÓ (ibid. 19). ÒIn constructing the world, mental sensations become properties of things, or, in other words, the subjective qualities build up the objective worldÓ (ibid. 77). Much of the Theoretical Biology is devoted to the di.erent steps of this process, which Carlo Brentari summarizes neatly: Òthe transcendental construction of the Umwelt is a semiotic process[...], the stimuli coming from the outside reality are translated into signs by the nervous system, then the physiologically produced signs are transposed outwards and, Þnally, they are experienced as objective qualities of the worldÓ (Brentari 2013: 17). 
Because it is the result of this active construction by the organism itself, the perceived or ÒintuitedÓ space of the Umwelt is not identical with physical space: Ò[s]pace as we think of it is the space with which the physicist deals, while intuited space as we look at it is the space of the biologist. 
The two are fundamentally di.erent from one anotherÓ (von UexkŸll, 1926: 42). This also means that each Umwelt belongs to the individual organism whose physiological processes give rise to it, so that there are Òas many worlds as there are subjectsÓ (von UexkŸll 1926: 70). The Þfth chapter titled ÒThe world of living organismsÓ introduces the notion of the functional circle, or Òfunction-circleÓ, a chapter on which was also added to the second edition of Umwelt und Innenwelt der Tiere the year after Theoretische Biologie was published. UexkŸll proposes the notion of the function-circle as a replacement for the too-linear idea of a reßex arc and deÞnes it thus: 
ÒEvery animal is a subject, which, in virtue of the structure peculiar to it, selects stimuli from the general inßuences of the outer world, and to these it responds in a certain way. These responses, in their turn, consist of certain e.ects on the outer world, and these again inßuence the stimuli. In this way there arises a self-contained periodic cycle, which we may call the function-circle of the animal.Ó (von UexkŸll 1926: 126). 
Within the function-circle, stimuli are registered as ÒindicationsÓ, and UexkŸll calls Òthe sum of the indications the world-as-sensed [Merkwelt]Ó (ibid.). The actions which the animal undertakes constitute the Òworld of actionÓ and together the world-as-sensed and world of action form the Òsurrounding-world [Umwelt]Ó (von UexkŸll 1926: 127). 
In the same year as Theoretische Biologie, UexkŸllÕs Staatsbiologie (1920) [Biology of the State] was published. In this book, UexkŸll uses his account of the organism as a whole structure according to a Þxed and pre-given Bauplan as a template to develop a deeply reactionary, hierarchical, and totalitarian conception of the state, which itself is likened to a biological organism. Organicism as a school of biological thought had many notable proponents in the Þrst half of the 20th century, UexkŸll is listed by Nicholson and Gawne (2015: 347) as one of them alongside Ludwig von Bertalan.y, Joseph Henry Woodger, Julius Schaxel, Emil Ungerer, Friedrich Alverdes, Kurt Goldstein, and Adolf Meyer. Nicholson and Gawne contrast organicism with both logical empiricism and vitalism, and the emphasis on the organization of the whole animal is widely seen as a middle way between a mechanistic reduction of the animal to its parts and the vitalist appeal to a separate life force in addition to the physical forces that act on non-living things. Organicism in German language biology and psychology was frequently extended into more general holistic worldviews that include culture and politics, where they take on a totalitarian character, culminating in the notion that ÒNational Socialism is politically applied biologyÓ (Harrington 1996: 175; Harrington clariÞes that the phrase is commonly attributed to the leader of the National Socialist Union of teachers Hans Schemm, even though no conclusive evidence for this attribution exists). Both UexkŸllÕs organicist approach to biology and his extension of a holistic view into a totalitarian politics expressed in biologistic tropes are part of broader tendencies in the discussions that formed the historical context he worked in. 
In 1924, UexkŸll was entrusted with Òa laboratory and an aquarium supplied by the Hamburg Zoological GardenÓ as an Òassistant scientiÞc collaboratorÓ at the University of Hamburg, Òa position almost comically beneath a man of his years and experienceÓ, and in 1926 he Òwas Þnally made an honorary professorÓ (Harrington 1996: 35). UexkŸll gradually developed the limited infrastructure into a budding research laboratory and in 1926 the Institut fŸr Umweltforschung [Institute for Umwelt Research] was founded at the University of Hamburg, of which UexkŸll was the director until 1940 (Harrington 1996: 35; Schnšdl & Sprenger 2021: 235 date the start of UexkŸllÕs tenure as director to 1925, while Brentari 2015: 34-35 dates the naming of the institute to 1927 and reports UexkŸll being the head of the institute only until 1936). This was the Þrst time he gained a secure Òinstitutional base for his researchÓ, at more than 60 years old (Harrington 1996: 35). ÒBetween 1926 and 1934 the Institute also published more than 70 scientiÞc works under the direct supervision of UexkŸllÓ (Brentari 2015: 35). In 1930, UexkŸllÕs Die Lebenslehre [The Theory of Life] was published. Even though UexkŸllÕs career situation had drastically improved only a few years prior, Ò[w]ith the beginning of the 1930s, o.icial German zoology grew even more hostile toward UexkŸll. The University of Hamburg stopped accepting as doctoral theses scientiÞc works that fell within the Þeld of research of the Umweltforschung, thus preventing their authors, often belonging to the institute founded by UexkŸll, from sitting the doctoral examination and obtaining the corresponding title.Ó (Brentari 2015: 37). Brentari links this negative perception of UexkŸllÕs research to the Nazi regimeÕs political motivations in funding biological research. Whereas genetics was heavily funded, UexkŸllÕs research was categorized as physiology and received little Þnancial support, since ÒUexkŸllÕs antidarwinism made his theories of little use to the Nazi regimeÓ (Brentari 2015: 37). 
In 1933 UexkŸll signed the Bekenntnis der deutschen Professoren zu Adolf Hitler, a declaration of support for Hitler penned and signed by German academics. The same year, UexkŸll incurred the scorn of Joseph Goebbels by holding a conference called ÒDas Duftfeld des Hundes [The dogÕs olfactory Þeld]Ó (Brentari 2015: 39). ÒGoebbels, the newly appointed Minister of Propaganda [É] wrote an articleÓ in which he complained that UexkŸll exempliÞed the tendency of academics to engage in useless intellectual endeavors instead of fulÞlling their duties imposed by societyÕs needs (ibid.). In the same year, the second edition of Staatsbiologie included a partially rewritten section on Òthe diseases of the state [Die Krankheiten des Staates],Ó which identiÞes members of foreign races who are detrimental to the state as ÒparasitesÓ (von UexkŸll, 1933: 59, 72). After GermanyÕs defeat in the First World War, UexkŸll had become increasingly antisemitic and began channeling this conviction in his academic writing (Mildenberger and Herrmann, 2014b: 294, 295). UexkŸll concludes the book by praising the Òingenious doctorÓ into whose care Germany has delivered itself as a Òdeeply sick patientÓÑa reference to Adolf Hitler (von UexkŸll, 1933: 79; Winthrop-Young, 2010: 226, 227). 
In 1934, UexkŸll received an honorary doctorate from the university of Kiel. In the same year, UexkŸll participated in two meetings of the Ausschuss fŸr Rechtsphilosophie der Akademie fŸr Deutsches Recht [Committee for Legal Philosophy of the Academy for German Law], a group of 17 scholars that includes Hans Frank and Alfred Rosenberg, who would both be sentenced to death in the Nuremberg trials for their involvement in Nazi crimes, and also Martin Heidegger and Carl Schmitt (Schnšdl & Sprenger 2019: 69). UexkŸllÕs totalitarian vision of an organismic state seems to have appealed to the conveners of the committee, who wanted to Òmake the concept of the organism fruitful for lawÓ, but UexkŸllÕs attendance is only documented for their Þrst two meetings, both in 1934 (ibid. 75). 
In the same year, StreifzŸge durch die Umwelten von Tieren und Menschen [A Foray into the Worlds of Animals and Humans] was published. This book would become UexkŸllÕs most popular and widely read work. It recapitulates many of the central themes of his thought until this point, often in simpler language or using more accessible comparisons, including his rejection of a machine theory of the organism and his notions of Umwelt and the functional circle. UexkŸll begins the work with his view that the Òmachine theory of living beingsÓ is fundamentally ßawed (von UexkŸll, 2010[1934]: 41). The Òmachine theoristsÓ hold that Òall living things are only machinesÓ and treat them as Òpure objectsÓ (von UexkŸll, 2010[1934]: 41, 42). Instead, biology can only understand the nature of organisms by treating them as subjects experiencing and inhabiting their own worlds (von UexkŸll, 2010[1934]: 41). UexkŸll advanced a model of how perception and action link the organismÕs nervous system with its environment in a functional cycle: Òeverything a subject perceives belongs to its perception world [Merkwelt], and everything it produces, to its e.ect world [Wirkwelt]. These two worlds, of perception and production of e.ects, form one closed unit, the environment [Umwelt]Ó (von UexkŸll, 2010[1934]: 42). He continues with an imaginative, metaphorical description of what the Umwelten of other subjects are: 
ÒWe begin such a stroll on a sunny day before a ßowering meadow in which insects buzz and butterßies ßutter, and we make a bubble around each of the animals living 
in the meadow. The bubble represents each animal's environment and contains all the features accessible to the subject. As soon as we enter into one such bubble, the previous surroundings of the subject are completely reconÞgured. [...] A new world arises in each bubble.Ó (von UexkŸll 2010[1934]: 43) 
This image of the Umwelt as soap bubble became one of the most popular bits of UexkŸllÕs writing, along with the example of the tick that he uses to show how di.erent other animalsÕ Umwelten are from ours. UexkŸll describes the very limited sensory and action-capacities of the tick and how they enable the completion of all the activities that constitute its life, while explaining the di.erence between a reßex arc and a functional circle along the way (44-52). StreifzŸge lays out UexkŸllÕs thought on the lives and environments of animals in the clearest and most accessible version, while still arraying many interesting ethological and physiological details, often accompanied by illustrative drawings. It progresses from the tick, over sea urchins, to mammals and humans, and concludes with an application of Umwelt to scientists, whose worlds are shaped by their theories and instruments much in the same way that the tickÕs world is shaped by its sensory and e.ector organs (133-135). 
In 1936, UexkŸll published an (auto)biographical work on the lives of his friends, Nie geschaute Welten [Worlds Never Seen]. In the same year, he followed an Òinvitation of the Academy of German lawÓ to speak at an event Òon philosophy of law at the Nietzsche-Haus in WeimarÓ (Brentari 2015: 41). When UexkŸll spoke out to defend the academic freedom of the university system and the need for research and teaching to proceed without interference from outside, Òthe audience interrupted UexkŸllÕs presentation and he leftÓ (Brentari 2015: 42). UexkŸllÕs thought was increasingly rejected, he was Òaccused of professing a Marx-inspired theory of environmentÓ and his autobiographical work Nie geschaute Welten Òwas o.icially banned from being displayed in the windows of bookshopsÓ (ibid.). In 1936, ÒUexkŸll was dismissed on account of his age with a very small pensionÓ (ibid.). In 1938, one of UexkŸllÕs last written works, the book Der Unsterbliche Geist in der Natur [The Immortal Spirit in Nature], appeared in print. In this book, UexkŸll recounts familiar themes of his thought through a Þctionalized narrative between di.erent characters, ending the book with a call for resurrecting the thought of the medieval mystic Meister Eckhart and an argument for why the human mind survives the death of the cerebrum. In 1940, the same year that his Bedeutungslehre [A Theory of Meaning] was published, he moved to Capri for health reasons (ibid.). 
Bedeutungslehre, which was published in English translation together with the slightly earlier StreifzŸge durch die Umwelten von Tieren und Menschen, develops an account of why the structures of living organisms Þt so perfectly into their environment of other organisms and the inorganic world. UexkŸll saw the Darwinist appeal to natural selection as an insu.icient explanation and instead regarded the harmonious composition of the natural world as evidence of a greater plan that orders the realm of the living into one overarching symphony of meaning, composed of countless melodies, harmonies, and counterpoints. As the concept of Umwelt grows out of UexkŸllÕs reading of Kant, so his musical theory of meaning grows out of romanticist holism and the neovitalism of Hans Driesch. UexkŸll and Driesch had met in Naples in the 1890s, where UexkŸll was researching the physiology of Eledone moschata while Driesch studied the development of sea urchins (Mildenberger and Herrmann, 2014a: 5, 2014b: 274Ð276). Driesch demonstrated that Òa sea urchin germ cell cut in half became not two half, but two whole sea urchins of half the size,Ó which to UexkŸll demonstrated that nature is not exhausted by mechanical explanation and warranted far-reaching conclusions: ÒEverything physical can be cut with a knifeÑbut not a melodyÓ (von UexkŸll, 2010[1934]: 194). UexkŸll agrees with Karl von Baer that there is a Ògoal-pursuing quality in the emergence of living beingsÓ and identiÞes musical harmony as the driving force of this teleological embryogenesis: 
Òplanned embryonic development [: : :] beings with the three beats of a simple melody: morula, blastula, and gastrula. Then, as we know, the development of the buds of the organs begins, which is Þxed in advance for every animal species. This proves to us that the sequence of formal development has a musical score which, if not sensorily recognizable, still determines the world of the senses. This score also controls the spatial and temporal extension of its cell material, just as it controls its propertiesÓ (von Uexku.
ll, 2010[1934]: 159, 160). 
To todayÕs reader, the role of the melody in this account of embryogenesis is at best a poetic placeholder that has to be replaced by scientiÞc explanations and at worst a kind of vital life force. The latter option is unfortunately very plausible, as Driesch was a leading proponent of neovitalism (Mildenberger and Herrmann, 2014a: 5, 6). The second philosophical source from which UexkŸllÕs musical theory of meaning draws its strength is a romanticist holism. The melodies, harmonies, and counterpoints are an explanation rather than a description of the organization of the biological realm only if we accept a holistic worldview in which wholes determine their parts in accordance to an overarching and preexisting schema, rule, or Òprimal image [Urbild]Ó (von UexkŸll, 2010[1934]: 159). This principle, which we saw in action in the embryogenic formation of a sea urchin in accordance to its Òprimal score,Ó goes back to GoetheÕs famous Urpßanze (160). Frederick Amrine has outlined UexkŸllÕs deep debt to Goethe, with whom he sides against Newton in the question of color perception (Amrine, 2015: 50). Amrine explains UexkŸllÕs musical theory of meaning as an instance of Goethean ecology, and his arguments are convincing: A central refrain in the Bedeutungslehre is developed from Goethe: 
ÒIf the ßower were not bee-like, If the bee were not ßower-like, The harmony would never succeed.Ó (von UexkŸll, 2010[1934]: 198) 
This is inspired by GoetheÕs lines, whichÑfollowing PlatoÕs allegory of the sun in Republic, Book VII in which Socrates calls the eye the Òmost sunlike of the sense organsÓ (Plato 2004: 203/508b4)Ñclaim that: 
ÒWere the eye not sunlike 
It could never gaze upon the sunÓ (von UexkŸll, 2010[1934]: 190). 
The vision of nature that UexkŸll expresses in musical terms is deeply grounded in romanticist holism, and the Òmeaning planÓ which guarantees that its parts, developing in accordance to their Òprimal imagesÓ and Òprimal melodies,Ó Þt into the overarching harmony is guaranteed by GoetheÕs Spinozist ÒGod-NatureÓ (von UexkŸll, 2010[1934]: 192). For UexkŸll, Ò[m]eaning is the pole star by which biology must orient itself, not the impoverished rules of causalityÓ (von UexkŸll, 2010[1934]: 160). 
In 1944, Òhis eightieth year, his reputation in Germany was of such a high nature that the University of Hamburg decided to nominate him for one of GermanyÕs most prestigious national awards, the Goethe Prize for Art and ScienceÓ (Harrington 1996: 71). Due to disruptions caused by the war, the prize was not awarded that year, and UexkŸll died in Capri in July of 1944 (see Harrington 1996: 71). 

2.3 UexkŸllÕs thought in parts and as a whole 
UexkŸllÕs thought has had a signiÞcant inßuence on a remarkable number of di.erent Þelds. Kalevi Kull (2001) lists philosophy, mathematics, linguistics, anthropology, literature, art, ethology, physiology, medicine, ecology, theoretical biology, and semiotics (Kull 2001: 12), while Frederick Amrine even considers him the Òfounder of two separate disciplines, ecology and semioticsÓ (Amrine, 2015: 47). Additionally, UexkŸll is considered a predecessor of cybernetics and today his work, especially his concept of Umwelt, is taken up in a variety of scientiÞc and technical Þelds, from psychology and cognitive science, over robotics and AI research to user experience design. 
UexkŸll inßuenced many well-known philosophers, especially in France and Germany, including Maurice Merleau-Ponty, Georges Canguilhem, Gilles Deleuze, Jacques Lacan, Helmuth Plessner, Max Scheler, Martin Heidegger, and Ernst Cassirer. Throughout the 20th century, UexkŸllÕs position in the history of ideas was somewhat ambivalent. Despite the real inßuence his thought had on many important thinkers, UexkŸll himself was never really read broadly or considered a major intellectual Þgure. Since the 1990s, and especially in the 21st century, something like a renaissance of interest in UexkŸllÕs thought has taken place (Kull 2020). Since 2001, there have been Þve monographs speciÞcally on UexkŸllÕs work, sixteen books that contain detailed discussions of his thought, three edited volumes, two special issues of journals, and Òmore than a hundred and sixty important research articles and essays that interpret UexkŸllÕs workÓ (Kull 2020: 484). The concept of Umwelt has thus moved from the footnotes and margins of cognitive science towards a central role in debates about the subjective experience of animal subjects, in particular in the embodied and enactive approaches to cognition. Since the later chapters of this dissertation deal with UexkŸllÕs reception in philosophy and cognitive science in detail, these topics will not be discussed here. Generally, aspects of UexkŸllÕs reception that are relevant to my arguments will be discussed in the speciÞc sections to which they pertain. In this section, I will focus on one speciÞc interpretation of UexkŸllÕs thought that draws into question the methodological viability of my entire project: 
Schnšdl and SprengerÕs UexkŸllÕs Surroundings: Umwelt Theory and Right-Wing Thought (2021) brings to light important new details about UexkŸllÕs involvement with the Nazi state, centrally his appointment in 1934 to the NazisÕ ÒCommittee for Legal PhilosophyÓ alongside thinkers like Heidegger and Carl Schmitt (70). This new discovery matches what was already knownÑUexkŸllÕs Staatsbiologie (1920) describes a totalitarian vision of the nation state conceived as an organism, and the second edition in 1933 praises Hitler, comparing him to a doctor with Germany as his sick patient. 
Additionally, Schnšdl and Sprenger discuss UexkŸllÕs reception by right-wing thinkers past and present, including Oswald Spengler, and identify the tension in his thought between individual autonomy and conformity to a larger plan as a central trope in the Conservative Revolution in Germany. This work is careful, novel, and clearly important. 
However, the overarching claims they make about UexkŸllÕs thought as a whole and what can and should be done with it are both very strong and, in my view, not su.iciently supported by the arguments and evidence they present. Broadly, these claims are Þrst that all of UexkŸllÕs thought forms one coherent and indivisible whole and second that this whole and all its parts have a totalitarian logic or essence. They are certainly right that some of UexkŸllÕs personal views and published thoughts are totalitarian, and that this goes beyond his bio-fascist Staatsbiologie. However, they claim that ÒUexkŸllÕs biology is always political, his Umwelt theory always a worldviewÓ and that if Òone side is split away and carried forward, the other side does not simply wither from neglect but is implicitly carried along as wellÓ (14, 230). If this were true, the wide-ranging use of Umwelt in biological research would have to bear traces of totalitarianism. The authors do not attempt to show such traces, nor do they make explicit what they might look like. This is problematic: When claiming that a whole area of scholarship is unknowingly importing totalitarian politics into their thought, the minimal due diligence would be to include a careful analysis of this research in your study to substantiate this claim. Conversely, if a study of contemporary papers employing the concept of Umwelt in biology or cognitive science found that they do not contain any noticeable totalitarian politics, this would show that Schnšdl and Sprenger are wrong, because these papers have successfully separated the concept of Umwelt from UexkŸllÕs totalitarianism, his biology from his politics, etc. Not only is the burden of proof plausibly borne by those making a positive claim, but it is also generally more di.icult to demonstrate the absence of something than its presence, since there is no concrete evidence to point at. On the other hand, since Schnšdl and SprengerÕs claim is that using the concept of Umwelt always unwittingly imports totalitarian thought, a single counterexample would technically su.ice to prove them wrong. It is at least di.icult to imagine which aspect of e.g. the algebraic formalization of Umwelt using Markov kernels in Lšhr and Ay (2015) could be considered totalitarian. 
The central link between biology and politics in the Staatsbiologie relies on interpreting the nation state as a biological organism. This is an ancient trope that goes back at least to the Roman consul Agrippa Menenius Lanatus, but importantly it does not follow from UexkŸllÕs concept of Umwelt or his biological research. It is not a part of UexkŸllÕs biological views, but a totalitarian belief which he also held and chose to combine with them in his theory of the state. If we reject the comparison between state and organism, the main link between UexkŸllÕs account of nature and any speciÞc political thought is gone. It is true that UexkŸll also talked about groups of humans as if they were species Þt by the Plan of Nature into di.erent environments, but nothing forces us to follow him in this point. Contrary to Schnšdl and SprengerÕs suggestions, UexkŸllÕs thought is not one organic whole, but a loose and shifting combination of di.erent ideas and inßuences that changes over time. They are adamant that no part can be simply removed from his work as a whole and used by itself, but they never make a convincing argument for why this should be so (and indeed the history of UexkŸllÕs reception seems to consist largely of examples of just this). They further claim that ÒUexkŸllÕs Umwelt theory cannot be separated from the problematic premises of its underlying holistic metaphysicsÓ (229). UexkŸllÕs metaphysical commitments are not easy to pin down, and itÕs not at all clear why they should be inseparable from the concept of Umwelt and how it functions as an account of animal experience and behavior. In general, the concept of Umwelt, inßuenced by Kant, can easily be separated from UexkŸllÕs holistic vision of Nature as a grand harmony, inßuenced by Goethe. UexkŸll needed the latter as an account for the complex relationships between all the di.erent parts of nature, because he rejected Darwinian evolution as an explanation. This conceptual separation between two roughly ÔKantianÕ and ÔGoetheanÕ parts of UexkŸllÕs thought is part of my reading of the term Umwelt developed in the next chapter. Contrary to Schnšdl and SprengerÕs claims, the two central senses in which UexkŸll uses the term Umwelt have nothing to do with politics and are conceptually independent from UexkŸllÕs own forays into totalitarian thought. 
Schnšdl and SprengerÕs account of UexkŸllÕs thought sometimes seems tailored to their own ends in ways that hinder clarity. They refer to his thought as a whole as ÒUmwelt theoryÓ, which makes it harder to di.erentiate between UexkŸllÕs (di.erent uses of the) term Umwelt and his many other ideas. Especially in the German edition, their choices of phrase often suggest that a strong connection between UexkŸll and environmentalism is an original part of his biological thinking, rather than a historical connection drawn later and by others (ÒUmweltÓ in current vernacular German primarily means ÒenvironmentÓ, and has strong associations with environmentalism). Another case in which the terminology is potentially misleading occurs when they attribute to the ÒUmwelt theoryÓ an Òidentitarian logicÓ (229). The term ÒidentitarianÓ has risen to prominence in the 21st century as the name of a racist, far-right political movement in Europe, and although they no doubt share some views that UexkŸll also held, ascribing an Òidentitarian logicÓ to his thought as a whole is anachronistic and characterizes it as political and reactionary in a way that is not plausible for large parts of his theoretical biology. There is a long, meandering, and somewhat vague line that leads from the Umwelt of a tick to a bio-fascist account of the state in UexkŸllÕs intellectual biography, but there is no ÔlogicÕ embedded in the concept of Umwelt that implies it, nor a ÔgermÕ contained within the idea of a functional cycle that inevitably buds into totalitarian thinking. 
Schnšdl and Sprenger are right to emphasize UexkŸllÕs totalitarian political views and their work on its historical context is immensely useful. However, their claim that UexkŸllÕs thought as a whole is irredeemably totalitarian and that no part of it can be separated from the whole and made use of in a di.erent system of ideas without importing also UexkŸllÕs reactionary political organicism is neither convincing as an interpretation of UexkŸll as a thinker, nor does it seem to be borne out by the reality of existing appropriations of the concept of Umwelt in the life sciences. 
It makes sense that UexkŸll himself would have wanted to perceive his own thought as an organic whole, but that does not mean that we as scholars can assume that each detail of his work can be explained as the unfolding of a single principle of thought. We can think of this as an overly internalist approach to historiography of science: When giving an account of the development of a particular idea or system of thought, two opposed methodological poles are ÔinternalismÕ and ÔexternalismÕ1. Internalism tries to explain the changes in a scientiÞc view by appealing to factors internal to the conduct of science and the development of scientiÞc concepts. An example of this would be explaining UexkŸllÕs move away from a mechanistic view and his increasing sympathy for DrieschÕs neo-vitalism as the result of both DrieschÕs and his own empirical work on embryology and physiology of sea creatures, respectively. In contrast, an externalist explanation of a position held by a scientist invokes factors that fall outside the strict boundaries of scientiÞc theory and practice, such as social, cultural, and historical context. An externalist explanation of why UexkŸll extended the view of nature as a coherent, meaningful whole arranged according to di.erent BauplŠne for its parts into a reactionary theory of the state might appeal to his biographical situation: From growing up in an aristocratic family in Czarist Russia to an impoverished researcher without a stable academic career in the democratic Weimar Republic, UexkŸllÕs personal fate explains why an organicist conception of state as a hierarchical and authoritarian Ôsocial organismÕ would be appealing to him personally. Extending his organicist, neo-Romantic view of Nature as a whole to the political sphere would have helped him make sense of his personal misfortunes. Such an externalist explanation seeks to explain 
e.g. why UexkŸll wrote Staatsbiologie without attempting to present this book as the logical consequence of the ideas he had developed until that point. 
1 These are distinct from other conceptual pairs called Òinternalism and externalismÓ, such as the opposing views on semantics. 
Schnšdl and SprengerÕs approach is strictly internalist in that it treats everything UexkŸll did and wrote as the result of a single inner logic of his thought, which they call Umwelt theory. However, states are not organisms, and there is nothing within UexkŸllÕs biological thought that implies that it should be possible to extend it to an analysis of human social relations. It is not surprising that UexkŸll did so, and Anne Harrington discusses UexkŸll as one of her case studies in a work on the links between holism in science and reactionary politics leading up to the Second World War (Harrington 1996). When Schnšdl and Sprenger treat UexkŸllÕs entire publication record as a complex whole structured only in accordance with a single inner principle, they are simply taking his commitment to organicism at face values, as if his mere support for the idea automatically established it as the design principle behind all of his writings. Instead, UexkŸllÕs writings at times resemble more a loose grouping of diverse inßuences. To understand how UexkŸll uses the term Umwelt and how it is later taken up by other thinkers, we have to distinguish between internal and external factors. In the next chapter, I show that UexkŸll uses the term Umwelt in two distinct senses when referring to the worlds inhabited by various animals and use this conceptual distinction to give an internalist explanation for some of the main disagreements about Umwelt in the literature. In contrast, UexkŸllÕs extension of his biological holism into a totalitarian politics should be explained largely through the historical context, which Harrington (1996) has already done. 

2.4Untangling Umwelt 
We have seen that UexkŸll combined his biological research with philosophical inspirations drawn primarily from Kant and Goethe to develop a theory of the worlds in individual animal subjects as Umwelten and of the complex relationships between all the di.erent organisms on earth as a system of melodies and harmonies arranged into one grand symphony. Responding to the historical circumstances of his time, he further extended his thought into a biologistic worldview which includes a totalitarian, organismic view of the state. My project focuses on the roughly ÔKantianÕ part of UexkŸllÕs thought and the term Umwelt at its center, which makes up the core of his major works and his inßuence on later thinkers. 
In contrast to Schnšdl and Sprenger, I do not think that we can develop an accurate understanding of UexkŸllÕs thought if we start with the assumption that everything he writes is part of one monolithic logical system unfolding over time. This is not just a far too optimistic view of the human mindÕs ability for logical coherence in general, but speciÞcally for UexkŸll this reading reproduces his own organicist views uncritically within the hermeneutic practice. Instead, I propose that we compare the various passages of UexkŸllÕs writings in which he discusses the same concepts carefully and take disagreements in the history of his receptionÑsuch as the question of whether Umwelt is constructed or selected, and whether an Umwelt belongs to an individual or to a speciesÑas signs that UexkŸllÕs thinking may be guided by two di.erent cognitive or conceptual frameworks at di.erent times, which leads him to use the term Umwelt in two importantly di.erent ways. This is the argument that I will spell out in the following chapter. 
Chapter 3: Two senses of Umwelt 
3.1 Interpreting Umwelt 
At the core of UexkŸllÕs achievement as a thinker at the interface between biology and philosophy lies the term Umwelt, which he uses to describe the worlds experience by di.erent animals according to the interplay between their physiologies and their habitats. This concept unites his own physiological research with the inßuence of KantÕs philosophy on his thought and functions as a point of departure for UexkŸllÕs reception by scientists and philosophers. In this chapter, I argue that UexkŸll uses the term Umwelt in two very di.erent senses, where one adopts the perspective of an external observer who has no access to the subjective experience of an animal and the other refers to the perspective which this animal itself has on the world that is given to it in subjective experience. This distinction has so far been neglected in the reception of UexkŸllÕs thought, but it has important consequences for how we evaluate his claims and how we can use the concept of to inform our perspective on animal minds and their subjective experience, which will be explored in detail in chapters 4 and 5. In brief, the two senses of Umwelt reconÞgure the question of whether Umwelt is open or closedÑa central concern of UexkŸllÕs commentators in 20th century French and German philosophyÑand shows that the term Umwelt cannot bridge the gap between the perspective of an external observer and the subjective experience of the animal itself. After some brief comments on UexkŸllÕs use of Umwelt in general, the next section will identify a central contradiction in UexkŸllÕs usage of the term Umwelt. The last section will introduce my distinction between two main senses of Umwelt as a solution to this contradiction and also demonstrate how this distinction helps resolve longstanding disagreements in the history of UexkŸllÕs reception. 
Throughout UexkŸllÕs writings, the word Umwelt emerges as the frontrunner from among a host of other neologisms for di.erent kinds of worlds, including Aussenwelt, Innenwelt, Merkwelt, Wirkwelt, Spiegelwelt, Gegenwelt, and Eigenwelt (von UexkŸll 2014[1921]: 63, 186). Many of these terms are slight variations of the same concept, or occur in di.erent contexts, and this terminological proliferation illustrates UexkŸllÕs attempts to construct a precise theoretical apparatus for expressing his views. Mildenberger and Hermann comment that Ò[u]nfortunately, UexkŸll himself never explained his use of the concept [Umwelt] in terms of a precise terminological deÞnition, as is usual in the natural sciences, but only indirectly in various passagesÓ (Mildenberger & Hermann 2014a: 4, my translation). They also emphasize how often UexkŸll describes and explains the concept of Umwelt in various publications, from its Þrst major occurrence in the Þrst edition of Umwelt und Innenwelt der Tiere in 1909 into the 1930s, with works like A Foray into the Worlds of Animals and Humans (Mildenberger & Hermann 2014b: 263). My claim is that the word Umwelt is made to serve di.erent functions throughout these di.erent passages, with some marginal uses but two distinct main senses. 
UexkŸll himself does not explicitly distinguish between two (or more) di.erent senses of Umwelt. His overall sympathies for holism, together with the centrality of Umwelt for his biological worldview, might also suggest that he was aiming for a single uniÞed concept of Umwelt that could connect and integrate the di.erent parts of his intellectual output. Whatever his own intentions and feelings about the matter may have been, I argue that the way he used the term Umwelt in his writings follows two main distinct senses. This interpretation is necessary in order to resolve a central contradiction I identify in UexkŸllÕs use of the term Umwelt, and also helps resolve existing disagreements about the precise meaning of Umwelt that have persisted throughout the history of UexkŸllÕs reception. 
Although UexkŸllÕs focus as a biologist is on a wide range of non-human animals, he also takes the concept of Umwelt to apply to humans qua animals, and he also extends the use of Umwelt in ways that are speciÞc to humans only. Geo.rey Winthrop-Young points out that Òhuman Umwelten are frequently located on interim levels between species and individualÓ, listing nations, regions, gender, and professions (Winthrop-Young 2010: 223-4). These uses of Umwelt as speciÞc to human social, cultural, and political groupings are marginal when seen in the context of UexkŸllÕs total literary production, and among the di.erent uses of Umwelt, they are also the furthest removed from the biological core of his thought. Unlike the main textual functions of Umwelt, its application to nations or professions is not grounded in UexkŸllÕs account of the biology of action and perception in a speciÞc environment or his physiologized Kantianism. If we consider UexkŸllÕs inßuence on science and philosophy, it is also the use of Umwelt to describe di.erent non-human animals or humans qua animals, not di.erent groups of humans, that is at the core of UexkŸllÕs reception. For these reasons, I focus on demonstrating the existence of two distinct main senses of Umwelt in UexkŸllÕs biological writings, without special attention to these other marginal uses of Umwelt. 

3.2 UexkŸllÕs Umwelt: a contradiction? 
If we look closely at the way that UexkŸll used the term Umwelt in his writings, we arrive at a contradiction: On the one hand, Umwelt is the sum of the possible perceptions (Merkwelt) and possible actions (Wirkwelt) of an organism, linked by its functional cycles, and the task of the biologist is to identify all these cycles of action-perception to form a complete picture of the organismÕs Umwelt. This conception lies at the heart of UexkŸllÕs methodological vision for biology, and the knowledge we can gain of other organismsÕ Umwelten is central to our scientiÞc knowledge of living nature. On the other hand, the Umwelt of an organism is the sum of its subjective experience, and UexkŸll is very explicit that these Umwelten are strictly private, and that any living subject can only ever know the contents of its own Umwelt. In this sense, our own Umwelt is a hard epistemic limit on our own knowledge, and UexkŸll repeatedly and explicitly emphasizes that no one can access the Umwelt of another subject. This creates a conundrum: Are Umwelten at the core of biological knowledge, or are they fundamentally unknowable? If one of these options is correct and the other one wrong, how can we make sense of the fact that UexkŸll makes both claims at various points? In this section, I will outline each of UexkŸllÕs two contradictory characterizations of Umwelt with relevant textual evidence to set the stage for my own solution to this dilemma of interpretation in the following section. [I begin 
UexkŸll assigns a central role to the concept of Umwelt in his account of biology, both in terms of its goals and how the researcher is to pursue them. For UexkŸll, a complete description of the Umwelt of an animal constitutes the culmination of all physiological and ethological studies of this creature. A comprehensive example of this process opens A Foray into the Worlds of Animals and Humans. Already in the foreword, UexkŸll gives a concise sketch of how biologists are to gain knowledge of animals by studying how perception and action link the organismÕs nervous system with its environment in a functional cycle: Òeverything a subject perceives belongs to its perception world [Merkwelt], and everything it produces, to its e.ect world [Wirkwelt]. These two worlds, of perception and production of e.ects, form one closed unit, the environment [Umwelt]Ó (von UexkŸll, 2010[1934]: 42). UexkŸll begins the introduction to the book by building up an account of the concept of Umwelt through a detailed discussion of the tick, which proceeds from a basic description of the animalÕs life and appearance to a critical engagement with physiology and the kind of knowledge it generates of ticks and other animals: 
ÒFor the physiologist, every living thing is an object that is located in his human world. He investigates the organs of living things and the way they work together just as a technician would examine an unfamiliar machine. The biologist, on the other hand, takes into account that each and every living thing is a subject that lives in its own world, of which it is the centerÓ (von UexkŸll 2010[1934]: 45). 
The contrast that UexkŸll draws here between the physiologist and the biologist is remarkable, given that much of his own empirical research falls squarely within the domain of physiology. Kristian 
KšchyÕs account is helpful here, as he describes a ÒCopernican RevolutionÓ in UexkŸllÕs thought in which the animals under study turn Òfrom objects into subjectsÓ of research (Kšchy 2022: 133, 134). He illustrates this through a comparison of UexkŸllÕs (1899) paper ÒVorschlŠge zu einer objectivierenden Nomenklatur in der Physiologie des NervensystemsÓ [Suggestions for an objectivating nomenclature in the physiology of the nervous system] co-authored with Theodor Beer and Albrecht Bethe and the ÒVorschlŠge zu einer subjektbezogenen Nomenklatur in der BiologieÓ [Suggestions for a subject-oriented nomenclature in biology], co-authored with Friedrich Brock in (1935). Kšchy highlights the parallel titles as well as the change of perspective from ÒobjectivatingÓ to Òsubject-orientedÓ terminology over the course of three and a half decades. Although UexkŸllÕs mature perspective on Umwelt and his own vision for a subject-oriented biology integrate physiological knowledge generated by other researchers and by himself, a fundamental shift in epistemic perspective seems to have taken place. 
UexkŸll describes the physiological process of how a stimulus gets transformed into a sensory experience by reference to Òperception cellsÓ that make up Òperception organsÓ, by which he means groups of neurons that make up areas of the brain responsible for processing speciÞc kinds of sensory information (von UexkŸll 2010[1934]: 47). Central to this account is the notion of the functional cycle: 

Fig. 2, the functional cycle, A Foray into the Worlds of Animals and Humans, p. 49. 
ÒThe connection of subject to object can be most clearly explained by the schema of the functional cycle [É]. The schema shows how subject and object are interconnected with each other and form an orderly whole. If one further imagines that subjects are linked to the same object or di.erent ones by multiple functional cycles, one can thereby gain insight into the fundamental principle of the science of the environment [Umwelt]: All animal subjects, from the simplest to the most complex, are inserted into their environments to the same degree of perfection.Ó (von UexkŸll 
2010[1934]: 49-50) 
For UexkŸll, the fact that each animal is perfectly Þtted into its Umwelt via its functional cycles follows from the relationship between e.ect world and perception world. Everything an animal can perceive Þnds its correlate in a meaningful action that is connected to this perception by a functional cycle. Since all the contents of the two worlds are linked in this fashion by functional cycles, and since the two worlds together make up the Umwelt (according to the deÞnition given in the foreword to A Foray), everything that exists in any animalÕs Umwelt is meaningful to its goals and a.ords purposeful behavior, rendering it perfectly Þtted into its Umwelt in this speciÞc sense. 
That UexkŸll considers our knowledge of an animalÕs Umwelt as the culmination of physiological and behavioral research into the animalÕs reactions to environmental stimuli also becomes clear in the Þnal section of Umwelt und Innenwelt der Tiere, where UexkŸll outlines 21 rules for biologists: 
Ò2. The Umwelt of any animal can be separated into a perception world and an e.ect 
world, which are united into a whole by the inner world of the body. [É] 
5. 
The functional cycles of animals begin with the perceivable features of objects, extend through the inner world of the body, and reapproach the object with the e.ectors [of the animal]. 

6. 
Thereby the object becomes the carrier of perceptual features on the one hand and the carrier of actions for the animal on the other. [É] 


12. The Umwelt is only indexed fully when all functional cycles (of the medium, the prey, the enemy, and the sexes) have been circumscribed.Ó (von UexkŸll 2014[1921]: 236, my translation) 
To recapitulate the context for the role of Umwelt in UexkŸllÕs thought from the previous chapter: UexkŸllÕs aim was to develop the conceptual foundations for a new biology that would be able to understand organisms as subjects acting in their own worlds, rather than just very complex objects in ours. To do so, biologists must identify which features in the environment can be perceived by the organism (Merkwelt) and what actions are a.orded to it (Wirkwelt). Further, the biologist identiÞes meaningful cycles of behavior called Ôfunctional circlesÕ which connect the two according to speciÞc needs of the organism. This yields e.g. a function circle for prey, one for shelter, one for procreation, and so on. In di.erent passages, UexkŸll refers to both the sum of Merkwelt and Wirkwelt and to the complete set of all functional circles of an organism as its Umwelt. In both cases, the Umwelt comprises the complete description of an animalÕs relationships to its environment which a biologist arrives at after an exhaustive study of this animal. In this account, Umwelt is not merely knowable, but it constitutes the goal of biological research and the pinnacle of our scientiÞc knowledge of animals. 
In stark contrast to its centrality for gaining biological knowledge, UexkŸll also maintains that the Umwelten of other subjects are fundamentally unknowable. He makes this explicit in his most popular work, A Foray into the Worlds of Animals and Humans. From the way UexkŸll characterizes Umwelt in this text, it is clear that this is no mere subset of the physical universe, but an individual and private world of phenomenal experience constructed by each organism. We can make inferences about the structure of an organismÕs Umwelt from its physiology and material surroundings, but the Umwelt of the animal can only be envisioned in our imagination (von UexkŸll 2010[1934]: 42). When UexkŸll takes us on Òa walk into unknown worlds,Ó he clariÞes that they Òare not only unknown; they are also invisibleÓ (2010[1934]: 41). UexkŸll uses the metaphor of a bubble to describe these worlds: 
We begin [...] before a ßowering meadow in which insects buzz and butterßies ßutter, and we make a bubble around each of the animals living in the meadow. The bubble represents each animal's environment and contains all the features accessible to the subject. As soon as we enter into one such bubble, the previous surroundings of the subject are completely reconÞgured. [...] A new world arises in each bubble. (2010[1934]: 43) 
We should note here that the image UexkŸll conjures is entirely Þgurative and Þctional: No subject will ever see a scene in which the Umwelten of other subjects are visible, as soap bubbles or in any other form. The Umwelt of each subject is made up of its phenomenal experience, and the experience of another subject is never a piece of phenomenal content or a perceptual object in this Þrst Umwelt, but always part of a di.erent Umwelt altogether, which belongs only to this other subject: 
ÒWe must therefore imagine all the animals that animate Nature around us, be they beetles, butterßies, gnats, or dragonßies who populate a meadow, as having a soap bubble around them, closed on all sides, which closes o. their visual space and in which everything visible for the subject is also enclosed. [É] [70] Only when we can vividly imagine this fact will we recognize in our own world the bubble that encloses each and every one of us on all sides.Ó (von UexkŸll 2010[1934]: 69-70) 
Already in Umwelt und Innenwelt der Tiere, UexkŸll is very explicit about the fact that the Umwelt of any living subject belongs only to this one organism and that Umwelten are private in both directions: no other subject can access this subjectÕs Umwelt, and this subject can never access any Umwelt other than its own. UexkŸll communicates this status of Umwelt as private and unknowable not just to his broader lay audience, but also accords it a central place in his account of biological methodology, devoting several of his 21 foundational rules for biologists to this issue: 
Ò3. In the Umwelt of each animal, there exist only things which belong exclusively to 
this animal. [É] 
14. 
The observer can only perceive the features acting on the animal as traits of his own world of appearances. The sensations of the animal remain forever hidden to him. 

15. 
Every animal carries its Umwelt around with it for all its life like an impenetrable shell. 

16. 
The same is true of the observerÕs world of appearances, which closes him o. completely from the universe, since it constitutes his Umwelt. [É] 


19. The world of appearances of each human being likewise resembles a hard shell, which constantly encloses them from birth until death.Ó (von UexkŸll 2014[1921]: 236.237, my translation) 
The image of the soap bubble is here replaced with the image of an impenetrable shell. While both of these Þgurative descriptions illustrate the idea of something enclosing the subject on all sides, there are important di.erences in their further connotations: The Ôimpenetrable shellÕ is not a barrier to the physical movement of objects, but a barrier to epistemic and phenomenal access. Any sensory experience we have is our own, so we can never see (or hear, or smell) someone elseÕs visual experience. Because it is in principle empirically inaccessible to us, the experience of others is not something we can gain empirical knowledge of. In contrast, the transparency of the soap bubbles indicates a kind of access. For a literal soap bubble, this accessibility is visual in an empirical sense, but the Umwelt-as-soap-bubble is open only to a speculative sort of vision: By using our poetic imagination, informed by scientiÞc knowledge, we can imagine what the Umwelt of a di.erent subject might look like. Importantly, this is an aesthetic activity that does not generate additional scientiÞc information beyond the physiological and ethological knowledge that informs it. 
The claim that everything a single living subject has access to is their own experience and never the experience of another may be plausible on the basis of personal experience or conceptual analysis, but UexkŸll also has more speciÞc reasons for making this claim. The privacy of subjective experience follows from his physiologized version of KantÕs account of the subject in Theoretical Biology. The process of how a living subject constructs its own phenomenal experience from stimulations to its nervous system was summarized in the preceding chapter. In brief, Òstimuli coming from the outside reality are translated into signs by the nervous system, then the physiologically produced signs are transposed outwards and, Þnally, they are experienced as objective qualities of the worldÓ (Brentari 2013: 17)Ó. Because both Òintuited space as we look atÓ and the objects we Þnd in it are the result of the Òpower of the subject that exercises this apperceptive activityÓ through the means of its own physiology, this space and theses objects belong only to this subject (ibid. 42, 16). On this view, two subjects encountering the same material object experience two numerically distinct (even if possibly qualitatively similar) phenomenal objects. As UexkŸll puts it: ÒThis is not a beech tree, but rather my beech tree, something that I, with my sensations, have constructed in all its details. Everything that I see, hear, smell, or feel are not qualities that exclusively belong to the beech, but rather are characteristics of my sense organs that I project outside of myselfÓ (unpublished autobiographical notes, quoted in Harrington 1996: 41). Your experience is yours because youÑnot meÑactively constructed it through an achievement of yourÑnot mineÑnervous system. UexkŸll links his own use of the term ÔconstructionÕ for the relationship that an organism has to its own Umwelt to Kant, explaining that Òwith Kant, we make the constructive activity of the subject the very center of our considerationÓ and identifying Òspace as the means whereby we construct external experienceÓ (von UexkŸll 1926: 19). Similarly, UexkŸllÕs belief that he experiences not the beech in itself but his beech follows from this Kantian account of construction: ÒIn constructing the world, mental sensations become properties of things, or, in other words, the subjective qualities build up the objective worldÓ (ibid. 77). The privacy of subjective experience a.ects the scientiÞc process of studying the minds of animals: 
ÒIn every instance where the qualities are known to usÑi.e. strictly speaking, only in our own caseÑwe may construct the world-picture directly from the objectivated sensations of the subject. Here the subject faces his appearance-world directly. Where we are denied a glimpse into the qualities [86] of the subject, we should not speak of an appearance-world, but only of a surrounding-world built up from our own qualities. Since our knowledge of the other subjectsÕ Ômark-signsÕ is denied us also, we are conÞned to determining what properties of our appearance-world have value as ÔindicationsÕ in the surrounding-world of an animal. These indications (which must become mark-signs for us, if we are to experience anything of them at all), we shall 
treat like our own qualities, so far as possible, and arrange them in the forms given us a priori. We see a justiÞcation for this proceeding in the fact that the anatomical structure of the sense-organs of animals brings together as a unity those indications that our attention also treats as uniÞed quality-circle. Nevertheless, we should never forget that, so long as we are concerned with biology, we must not for an instant desert our posts as observers from the outsideÓ (ibid. 85.86). 
UexkŸll emphasizes that this fundamental privacy of an individual Umwelt applies also to humans, and that each human person occupies a Ôcenter-stageÕ position in their own life insofar as each of us as a Òcreature constitutes the center of its UmweltÓ (von UexkŸll 2014[1921]: 236). This passage connects the epistemic limitations encountered by the biologist to the more general way in which we encounter other human beings: 
Ò[É] Our whole memory is like the rigging-loft of a theatre with wings Þlled with schemata, which from time to time appear on the stage of our consciousness, not in their own character, but dressed up in the content-qualities of our mind. It is most unfortunate that we can never behold the consciousness-stage of another living being; nothing would be more instructive than to see the world through the schemata of another. But at least let us never forget, as we watch our fellow-men going to and fro around us, that they are treading the boards of our stage, and we theirs. The stages are never identical; in most cases, indeed, they are fundamentally di.erent. And we can never hope to play on the stage of others the role that we play on our own.Ó (ibid. 96-97). 
At this point we are facing a seeming contradiction: On the one hand, UexkŸll develops his own vision and methodological guidelines for a biology that focuses on animals as living subjects. In this account, the Umwelten of di.erent animals are the primary targets of scientiÞc research, and the progress of biological knowledge about any particular animal can be measured by our increasingly comprehensive knowledge of its Umwelt. On the other hand, UexkŸll describes the Umwelten of other subjectsÑprimarily the non-human animals studied by biologists, but ultimately all animals, including humansÑas fundamentally private, empirically inaccessible and ultimately unknowable to others. How can this contradiction be resolved? 
One possible hypothesis would be that UexkŸllÕs use of the term Umwelt underwent a historical development in which its meaning changed from one of these versions to the other. Indeed, there are interpretations of UexkŸllÕs thought in the literature that describe such a change and partly map onto the di.erences in the two use-patterns of Umwelt just described. First, the development in UexkŸllÕs thought described by Kšchy as a move from Òthe physiological UexkŸllÓ to the Ò(umwelt-)biological UexkŸllÓ outlined above resonates with some aspects of this problem of interpretation (Kšchy 2022: 117). Is this seeming contradiction perhaps just a move from an earlier, physiological view of Òliving beings as objectsÓ to a later, biological view of Òliving beings as subjectsÓ (Kšchy 2022: 117)? Similarly, Brentari divides UexkŸllÕs thought into Òa Þrst ÔendosemioticÕ phase, whereby the construction of the Umwelt is mainly seen as being based upon physiological processes, and a second, ÔexosemioticÕ one, which is more directly centred on the role of signs and meanings in animal behaviourÓ (Brentari 2013: 8). However, such a historical periodization cannot dispel the apparent contradiction in our case, because both Umwelt-as-knowable and Umwelt-as-unknowable are distinctly present in the same phases of UexkŸllÕs career, and indeed in the same texts. The above accounts of the two use-patterns of Umwelt both draw on important sections from Umwelt und Innenwelt der Tiere as well as A Foray into the Worlds of Animals and Humans. The two incompatible uses of Umwelt were present in a single book together in 1909 and again in 1934, so their incongruity cannot be explained as a change in UexkŸllÕs views. Instead, I argue that UexkŸll, throughout his major works and across the span of his writing career, uses the term Umwelt mainly in two distinct and di.erent senses. Once we di.erentiate between the two, the passages cited above are no longer in contradiction, but instead o.er complementary accounts of the environments of animals that employ two very di.erent senses of the word Umwelt. 

3.3 The solution: two di.erent senses of Umwelt 
In his account of HeideggerÕs UexkŸll-reception, Carlo Brentari outlines the basic coordinates of any investigation into animals and their environments: 
ÒIn general, the problem of the relationship between the animal and what surrounds it can be dealt with from two perspectives. In the Þrst, one can investigate how much the animal perceives from the environment; it is the line of investigation followed by all the researchers that are dedicated to the quantitative measuring of the wavelengths heard by an animal, or the color spectrum that it can see. In the second perspective, which is much more complex, one tries to understand how the animal experiences what it perceives, how it categorizes the perceived; even though some of the interpreters believe the opposite, this is the line of investigation that UexkŸll follows, which sees in it a fecund application of Kantian transcendental philosophy to biology.Ó (Brentari 2015: 199) 
The italics in this passage are important, as they mark the crucial di.erence between the two perspectives which Brentari goes on to describe as Òquantitative and qualitativeÓ (2015: 199). The two main senses in which UexkŸll uses the term Umwelt, and which give rise to the contradictory accounts of Umwelt as somehow both the aim and pinnacle of biological knowledge about animals, as well as a fundamentally unknowable private world of subjective experience belonging to each living creature, correspond to these two perspectives. UexkŸllÕs thought is so fascinating because he adopts both of these perspectives at various points, but it is di.icult to parse because he uses the term Umwelt in both cases, without making it explicit which perspective is being adopted in any particular passage of text. 
From the perspective of an external observer, such as a scientist, the experience of an animal is invisible, and only its behavior can be observed. When adopting this perspective, the Umwelt of the animal under study refers to a conceptual construction that holds together our knowledge about the individual elements of the animalÕs environment, its physiology, and its behaviors that connect the two through functional cycles. Umwelt here is a higher-order piece of scientiÞc knowledge that is assembled from the results of empirical research. Since this is the perspective from which UexkŸll developed his methodological principles for what would become the Þeld of ethology, I call this sense of the word Umwelt the ethological Umwelt, or e-Umwelt for short. 
From the perspective of the animal itself, its Umwelt is just what it knows as the world. This is the world each of us sees when we open our eyes, or touch when we reach out our hands, etc. We might call this a Þrst-person perspective, as long as we do not confuse it with the category of grammatical person. Almost no animals have language, but all animals have an Umwelt. This perspective emphasizes the status of the world as experienced by a particular subject. Whereas I would normally describe the objects I see before me in a way that treats my perceptual experience as if it were universal and neutral (Ôthe book is blueÕ, rather than ÔI experience the book as blueÕ), this Þrst-person perspective emphasizes that all perception is subjective experience, and the world insofar as we can perceive it is always the world of our own subjective experience, our Umwelt. Since this focus on the experiential character of the world as it presents itself to a single living subject is also at the core of phenomenology, I call this second sense of Umwelt the phenomenological Umwelt, or p-Umwelt. 
There is one point at which this analysis deviates from the Brentari quote above: In BrentariÕs account, it sounds as if UexkŸll fully adopts the second perspective for his conception of biology. We would then expect his descriptions of how biologists are to proceed in their work to concern p-Umwelt. Importantly, this is not the case. Despite his contrasts between physiologists and biologists, or physicists and biologists, in which the biologists are characterized as concerned with subjects where their colleagues see only objects, when it comes down to the methodological and conceptual structure of biology itself, UexkŸll is explicit that p-Umwelt is beyond the limits of scientiÞc knowledge and only e-Umwelt is what scientists are concerned with: 
ÒIt is completely impossible for us to get an immediate insight into the conscious experience of any living being other than ourselves. This much will be readily admitted. In contrast, the comparative psychologists endeavor to make assertions about the consciousness of animals indirectly through analogical conclusion. They appeal to the fact that in our conduct with our fellow humans, we constantly make inferences about their conscious experience based on their utterances and conclude that we are allowed to apply the same procedure to animals with some criticism. This conclusion is not proper for biology. The biologists deals only with the objective changes in the animal kingdom, because only these are accessible to the external observer. [...] Therefore only the body of animals is the sole research object accessible to us and not their consciousness.Ó (von UexkŸll 2014[1921]: 233-234) 
According to this judgment, UexkŸll-the-biologist only writes about e-Umwelt. Whenever the subjective experience of an animal is thematized directly, we are reading UexkŸll-the-popular-author, such as in the passage about soap bubbles. The di.erence between e-Umwelt and p-Umwelt can be illustrated helpfully by contrasting UexkŸllÕs own diagram of a functional cycle with a drawing by Ernst Mach. The e-Umwelt is a scientiÞc concept made up of the various functional cycles connecting perception world and e.ect world, which in turn can usefully be represented via a diagram: 

Fig. 3, a functional cycle as depicted in Theoretical Biology (1926), p. 155 
In contrast, the p-Umwelt of an animal is the sum or totality of its subjective experience. Because we tend to focus on our visual sense to the detriment of hearing, smell, etc., the p-Umwelt can be illustrated via the drawing of the Þrst-person perspective: 

Fig. 4, Ernst MachÕs Innenperspektive, Wikimedia Commons 
With the distinction between e-Umwelt and p-Umwelt, the seeming contradiction is resolved: e-Umwelt occupies a central place in UexkŸllÕs account of how biologists should study the world, while p-Umwelt is fundamentally private and therefore not accessible to scientiÞc investigation by external observers. But this distinction between two senses of Umwelt solves other problems, too. Throughout the reception of UexkŸllÕs thought, there have been di.ering interpretations of Umwelt along two axes: 
1.
 ÒDo Umwelten exist for individual animals or whole species?Ó and 

2. 
ÒAre Umwelten sets of elements selected from an objective material world, or are they mental constructions?Ó (Feiten, Holland, and Chemero 2020: 4). 


These questions have given rise to controversy. Brentari argues that Òa chief hermeneutic line has overcome the othersÓ which holds that the Òthe constitution of a species-speciÞc Umwelt is a selective processÓ and has Òunderestimated, if not completely neglectedÓ the Kantian aspect of UexkŸllÕs theory and its emphasis on the construction of the Umwelt by the subject itself (Brentari 2013: 16, 17). Similarly, Hermann and Mildenberger report that: 
ÒUntil today, the history of the reception of UexkŸllÕs idea moves between two extreme views: between an ÔUmweltÕ which is a production of the animal and ultimately comes close to a subjective worldview-construction of this animal, or an ÔUmweltÕ which is merely the container of all the environmental elements of an animal. UexkŸll would doubtlessly orient himself towards the former view.Ó (2014b: 264) 
These commentators are right that UexkŸllÕs thought accords a central place to the idea that each animal subject constructs its own Umwelt. Because the material involved in this construction-process undergoes a total transformationÑfrom features of the physical environment, over stimuli a.ecting sensory organs, into nervous excitation, transformed into signs, and Þnally transposed outwards as phenomenal qualitiesÑthis achievement cannot be described as a mere ÔselectionÕ. Brentari emphasizes that Òinterpreters who see the environment as [purely] the result of the perceptive selection that sense organs exercise on external realityÓ fail to appreciate that Òthe meaning of the Umwelt does not derive from objective pre-existing connections, but is established by the animal subjectÓ (Brentari 2015: 234). And yet, UexkŸll himself frequently describes Umwelt as the result of a selection. His chapter on sea urchins in Umwelt und Innenwelt der Tiere contains a section titled ÒUmweltÓ, which follows a section on the combination of stimuli and begins by asserting that Òthe treatment of the combinations of stimuli by the sea urchins is so important because it answers the question of the constitution of the UmweltÓ (von UexkŸll 2014[1921]: 112). According to UexkŸll the morphology of the sea urchin is Ògoverned by a uniform plan, which draws the whole surroundings of the sea urchin into its organizationÓ (ibid. 113). This plan Òselects among the useful and inimical items in the surroundings those e.ects, which are suitable as stimuli for the sea urchinÓ (ibid. 113). Here UexkŸll is clearly describing Umwelt as the result of a selection process. Likewise in A Foray, UexkŸll writes that Ò[t]he animal's environment, which we want to investigate now, is only a piece cut out of its surroundings, which we see stretching out on all sides around the animalÓ (von UexkŸll 2010[1934]: 53). 
With regards to the question of whether an Umwelt belongs to a species or an individual, Mildenberger and Hermann state that it Òwas not entirely clear, whether [UexkŸllÕs concept of Umwelt] referred to an individual or a genusÓ (2014b: 247). They themselves ascribe the latter view to UexkŸll: ÒAccording to his theory, every animal species inhabits a particular Umwelt which is made up only of things that the animal in question can detect with its sensory organsÓ (Mildenberger & Hermann 2014a: 5, my translation). This sentence contains a curious shift from Òanimal speciesÓ to Òthe animal in questionÓ, echoing UexkŸllÕs habit of using a generic singular such as Òthe tickÓ to describe ticks in general rather than a particular concrete individual. 
The distinction between two senses of Umwelt is helpful for these two questions of interpretation because all uses of Umwelt found in UexkŸll can be given a meaningful interpretation, whereas any attempt to choose just one answer to either questionÑUmwelt concerns only selection, only construction, only species, or only individualsÑwould inevitably have to contend with conßicting textual evidence from UexkŸllÕs writings. Instead, we can assign e-Umwelt and p-Umwelt to the di.erent options: Whenever an Umwelt is selected from the elements of the animalÕs surroundings, we are talking about e-Umwelt. Talking about a larger set of elements from which only a subset is selected only makes sense if we adopt the position of an external observer. From the perspective of the animal itself, there are only objects of experience, i.e. only objects which are part of its p-Umwelt. Additionally, the larger set from which only some items are selected is comprised of objects in the observerÕs p-Umwelt (or physical objects in physical space, if we speak from an imagined neutral perspective), so selecting a subset of them is not enough to constitute the p-Umwelt of the organism under study. Instead, this p-Umwelt has to be constructed. References to the construction of Umwelt then most likely refer to p-Umwelt, as UexkŸllÕs physiologized Kantianism tells a story of how it is that an individual subject gets to have experiences. Whenever we talk about p-Umwelt, we are talking about an individual animal (concrete or hypothetical), because only individuals, not species, have experience (at least according to UexkŸllÕs writings). Therefore, any reference to the Umwelt of a species should be interpreted as e-Umwelt, potentially as a kind of abstraction over the actual e-Umwelten of all actual members of the species, or an idealized e-Umwelt derived from a conception of the species which belongs to no concrete individual. The di.erent positions on these two questions that are taken up throughout the history of UexkŸllÕs reception only appear to be in direct contradiction so long as we fail to distinguish between e-Umwelt and p-Umwelt. My view that the term Umwelt is used equivocally in two importantly distinct senses thus helps explain the persistence of this hermeneutic controversy in the literature and also resolves the dilemma. 
Chapter 4: Are Umwelten open or closed? 
4.1 A central question, so far neglected 
In the preceding chapter, I introduced a distinction between two senses of Umwelt, an ethological and a phenomenological one, which has important consequences for how we read UexkŸll, for the conceptual foundations of embodied cognitive science, and for how we think about minds in general. Crucially, this distinction depends on UexkŸllÕs conviction that an individual can never have direct access to the subjective experience of another living subject. This experience of the other constitutes their p-Umwelt, while the external description to which a scientist must limit themselves constitutes its e-Umwelt. P-Umwelt and e-Umwelt of a single individual are not just numerically non.identical, they are also fundamentally di.erent kinds of entities. The scientist relies on this external construction of an e-Umwelt, because the p-Umwelt of the living subject under study is in principle inaccessible to them. If the scientist had direct access to the p-Umwelt of another subject, the distinction between the two senses of Umwelt would be unnecessary and the scientist would simply study and describe the p-Umwelten, or Umwelten simpliciter, of various animals. It is only because the p-Umwelten of individual subjects are closed o. to each other that this distinction, on which my entire argument is based, makes sense. 
UexkŸll believed that the Umwelt of each individual animal, human or non-human, is closed. However, from the time of his earliest impact on French and German philosophy to the current debates in the philosophy of cognitive science, thinkers who are inspired by UexkŸllÕs thought and seek to use the concept of Umwelt for their own work are almost unanimously united in their rejection of the idea that each individualÕs Umwelt is closed and separate from those of every other subject, at least in the case of humans (see Feiten, Holland, and Chemero 2020, Brentari 2015: 175-217). Since there is such wide-spread agreement on this question, it would be tempting to assume that UexkŸll must simply be wrong on this point. The function of this chapter is to show that the issue is not as simple as that once we distinguish between e-Umwelt and p-Umwelt. The various claims made about Umwelt being open or closed turn out to concern two di.erent questions: Is e-Umwelt open or closed? And is p-Umwelt open or closed? Additionally, there are also thinkers who use Umwelt in an way that is so di.erent from UexkŸllÕs use that their diverging assessment is not truly in conßict with UexkŸllÕs, they are instead addressing other questions that function according to the structure of their own philosophical systems. When evaluating what exactly is being claimed about e-Umwelt and p-Umwelt when they are said to be open or closed, and what kind of arguments would be necessary to support these claims, a stark di.erence appears: Whereas there are many good arguments readily available for treating e-Umwelt as open, claiming that p-Umwelten are open requires speciÞc philosophical commitments about the metaphysics of subjective experience. It will turn out that treating e-Umwelt as open or closed is a methodological choice that depends on whether a study is interested in a diachronic or only in a synchronic view of an organism. In contrast, the question of whether p-Umwelten are open or closed concerns whether subjective experience is fundamentally private, or whether there are instances where a single subjective experience is shared by two or more subjects. What this means is that the many good arguments for studying open e-Umwelten do not show that p-Umwelten are open. 
These distinctions will also form the backdrop for my discussion of embodied cognitive science in chapters 5 and 6. In chapter 5, the focus lies on separating arguments for the openness of e-Umwelt from those that could support the openness of p-Umwelt. In chapter 6, I discuss a view that endorses the openness of p-Umwelt and draw into question the argumentative role that an analysis of our own subjective experience can play for demonstrating the openness of p-Umwelt. Before I develop my own way of distinguishing between di.erent claims in this chapter, I consider four of the most famous views endorsing open Umwelten held by Maurice Merleau-Ponty and Gilles Deleuze in France, and Martin Heidegger and Ernst Cassirer in Germany. 
In Merleau-PontyÕs late work, focused on an ontological treatment of the same questions he had addressed in terms of human subjectivity in the Phenomenology of Perception (2002), UexkŸllÕs concept of Umwelt plays a central role, but crucially always characterized as open (see Feiten, Holland, and Chemero 2020: 8-10). From the Òtype of being which our experience of the earth and the body reveals to us,Ó Merleau-Ponty derives a Òphilosophy of the world as O.enheit der UmweltÓ, he characterizes the Òopenness of the UmweltÓ as a Òmilitant ÞnitudeÓ and it even Þgures in his investigation of the relationship between subject and object as Ò[t]he true solution: O.enheit of the Umwelt, Horizonhaftigkeit. [sic]Ó (Merleau-Ponty 1988: 190-191; Merleau-Ponty 1968: 251, 196). 
Gilles Deleuze mentions UexkŸllÕs thought on several occasions but draws on it at length in his (1988) Spinoza: Practical Philosophy to give an account of SpinozaÕs ethics not as a moral philosophy but as a philosophical ethology (see Feiten, Holland, and Chemero 2020: 10-16, Deleuze 1988: 125). After asserting that UexkŸllÕs Òapproach is no less valid for us, for human beings, than for animals,Ó Deleuze goes on to characterize this approach in a way that is antithetical to UexkŸllÕs actual work (Deleuze 1988: 125). For Deleuze, a Òbody can be anything; it can be an animal, a body of sounds, a mind or an idea; it can be a linguistic corpus, a social body, a collectivityÓ, and the philosophical ethology appropriate to such a proliferation of bodies involves Òthe laying out of a common plane of immanence on which all bodies, all minds, and all individuals are situatedÓ, such that there is Òno longer a subject, but only individuating a.ective states of an anonymous forceÓ (Deleuze 1988: 127, 122, 128). This departs signiÞcantly from UexkŸllÕs approach, on which Umwelten Þrst and foremost belong to animal bodies (and to social bodies only by an ill-advised metonymic extension, as I have argued in chapter 2), and each subject together with its mind is cordoned o. in its own Umwelt, instead of inhabiting one shared plane of immanence. 
In Germany, as in France, UexkŸllÕs most well-known philosophical readers were enthusiastic about his thought and drew on the concept of Umwelt for their own work, but parted ways with UexkŸll on the question of whether Umwelten are open or closed. Both Heidegger and Cassirer argued that among all animals, humans alone are not locked into individual private Umwelten, but instead share access to one common world (see Brentari 2015: 198-204 and 188-194). Heidegger maintained that UexkŸllÕs Òinvestigations are very highly valued today, but they have not yet acquired the fundamental signiÞcance they could have if a more radical interpretation of the organism were developed on their basisÓ (Heidegger 1995: 263, quoted in Buchanan 2008: 53). On the basis of his own investigation of Dasein, Heidegger concluded that Òthe stone (material object) is worldless; the animal is poor in world; man is world-formingÓ (Heidegger 1995: 177, quoted in Buchanan 2008: 43). 
Cassirer likewise assigned a special status to humans. He discussed UexkŸll at two di.erent points in his work, positively drawing on UexkŸllÕs thought for his discussion of epistemological questions in biology and again in the development of his own philosophical anthropology (Stjernfelt 2011, Brentari 2015: 188-194). In the planned fourth volume of his Philosophie der symbolischen Formen, drafted in 1928 but only recently published, Cassirer emphasized the di.erence between animals and humans as the Òanimal symbolicumÓ (Stjernfelt 2011: 172). Cassirer draws on UexkŸllÕs account of animal Umwelten, but sharply contrasts it with his own philosophical anthropology: Òanimals are deÞned as living beings that, contrary to man, are conÞned to closed UmweltenÓ (Stjernfelt 2011: 180). On CassirerÕs view, playing on a popular refrain in philosophical anthropology according to which the human is unique among animals as a Mangelwesen, a Ôcreature of lackÕ, we are forced to construct the human social world through cultural and technological means because we are not successfully Þtted into our environment via our instinctual behaviors in the way animals are: 
ÒWhile the animal is locked, in direct perception-action chains, to certain aspects of reality, aspects functioning as ÔsignalsÕ only, never as objects, man is able to step back 
and contemplateÑand indeed constituteÑworldly objects at a creative distance. Man is so to speak driven out of the paradise of Umwelt with its close-knit perception-action circuits and he is thus condemned to build his own Umwelt, which he may do because he is Ôder Form fŠhigÕ, he is Ôcapable of formÕ. (Cassirer 1995: 46, 1996: 44, as quoted in Stjernfelt 2011: 173). 
This leads Cassirer to the view that animal Umwelten, but not human ones, are closed: Òthe animal Umwelt forms an impenetrable shell around the animal, quite unlike the plastic and malleable human Umwelt, subject to ongoing further elaboration, investigation, and constructionÓ (Stjernfelt 2011: 173). In StjernfeltÕs account, it sounds as if Cassirer is in agreement with UexkŸll on this point, indeed he writes that the former Òinherit[s] the same sharp distinction between animal closure and human opennessÓ from the latter (Stjernfelt 2011: 174). This is surprising, since UexkŸll repeatedly states that individual humans are closed in their private Umwelten in the same way that other animals are. The source of this confusion lies in a distinction between di.erent senses of openness, which will be discussed below, but also in two di.erent kinds of Kantianism: On CassirerÕs view, Òthe Umwelt of man can not be constructed on the basis of the Bauplan of human anatomy, unlike the case in animals whose Umwelten are exactly so deÞnedÓÑbut this is exactly what UexkŸll does for humans and other animals. In his own account, UexkŸll freely moves back and forth between humans and ticks, explains the constitution of human perceptual space as three-dimensional via the three semi-circular canals in our inner ear, and describes the kinds of Umwelten that belong to natural scientists as separate, in contrast to CassirerÕs view of a common culturally constructed world (von UexkŸll 2010[1934]: 52, 56, 133-135). Whereas for Cassirer, a Neo-Kantian of the Marburg school, the role of forms for human cognition is the crucial element that distinguishes our Umwelten categorically from those other animals, UexkŸll, who likewise presents his own views as grounded in KantÕs account of the subject, moves away from Kant precisely when he replaces the function that time and space serve as pure form of sensible intuition with the functional anatomy of our cochleaÑat most a sort of Ôphysiologized KantianismÕ (see Stjernfelt 2011: 171, see von UexkŸll 2010[1934]: 52, see also Feiten, Holland & Chemero 2020: 5). 
Despite the substantial di.erences between their fundamental philosophical perspectives and commitments, these four philosophers in France and Germany are united not just by their enthusiasm for UexkŸllÕs ideas as fruitful material for philosophical development, but also by their conviction that human individuals do not inhabit private, closed Umwelten. If they are right that the Umwelten of humans, or of all animals, are open to each other, UexkŸllÕs theory of Umwelt, in the interpretation I have proposed in the preceding chapter, requires at least substantial philosophical revision. Worse, the very distinction between p-Umwelt and e-Umwelt, the central piece of my overall position, would be in danger of breaking down: If the scientist could study the p-Umwelt of another subject directly, there would be no need to develop an account of an e-Umwelt. Therefore, the question of whether Umwelt is open or closed is of crucial importance for my project. Adjudicating these issues requires not just determining whether these thinkers are right to disagree with UexkŸll, but Þrst to determine more precisely what that disagreement consists of in each case. 
The question of whether Umwelt is open or closed is not just important for my own project, it is also one of the central questions in UexkŸllÕs overall reception. In his magisterial monograph on UexkŸllÕs thought, Carlo Brentari (2015) identiÞes two main debates within the reception of the biologistÕs work, about whether an Umwelt is selected or constructed, and whether it belongs to a species or to an individual organism. In the last chapter, we have seen that my distinction between two di.erent senses of Umwelt reconÞgures the discursive constellations of these debates in helpful ways. It became clear that both sides of each debate can be right, if they are interpreted as referring to the two di.erent senses of Umwelt. The historical failure of these debates to produce agreement on a single position makes sense in this light: Since some characterizations are true of e-Umwelt but false of p-Umwelt, and vice versa, scholars who think they are locked in a debate about a single concept called Umwelt while they are actually making claims about the two di.erent concepts of e-Umwelt and p-Umwelt are bound to talk past each other. But there is a third major source of disagreement in the reception of UexkŸllÕs thought, perhaps of even higher philosophical signiÞcance than the other two. This is the question of whether Umwelt is open or closed. In this chapter, I argue that this question has not been discussed in a satisfactory manner either in UexkŸllÕs reception or in the secondary literature on it, in part because the distinction I have pointed out between two di.erent senses of Umwelt was not recognized. Because there are two di.erent senses of Umwelt, there are also two di.erent senses it which it can be claimed to be open, and two senses in which it can be said to be closed. Only by di.erentiating between them can we start to unravel the original question. 
The sheer volume of di.erent accounts that proclaim the openness of (human) Umwelt can make it seem as if the matter has been settled conclusively. Additionally, secondary literature on UexkŸllÕs reception unfortunately often limits itself to recounting these critiques of his claim about the closure of Umwelt, without really evaluating their theoretical strength. By distinguishing the di.erent ways in which an ethological and a phenomenal Umwelt can be said to be open or closed, I provide the missing framework for distinguishing more clearly between the scope and content of the di.erent claims present in the literature and assessing which of these convincingly argue against UexkŸllÕs view that Umwelt is both ethologically and phenomenally closed. On this analysis, it turns out that ethological Umwelten are open, but phenomenal Umwelten appear prima facie closed and can only be Ôopened upÕ by taking onboard metaphysical commitments that are both strong and somewhat unclear. 
In section 4.2, I give a brief critical overview of how the topic of openness and closure of Umwelten is represented in contemporary scholarship on UexkŸllÕs thought and its reception, motivating the need for a more systematic discussion. Section 4.3 breaks down Þve di.erent claims that can be made about the openness or closure of Umwelt, depending on which sense of ÔUmweltÕ is used and provide some examples from the literature to illustrate the di.erent claims about openness and closure. Section 4.5 summarizes the analysis in this chapter and its signiÞcance for my own argument and for UexkŸll studies in general moving forward. 

4.2 Unsatisfying engagements 
The question of whether Umwelt is open or closed plays an important role both in UexkŸllÕs reception and in contemporary UexkŸll studies, but I claim that these engagements are ultimately unsatisfying. In this section, I highlight this problem through two examples, one from the 20th century philosophical reception of UexkŸllÕs thought and contemporary secondary literature commenting on it, and another example from 21st century UexkŸll studies. In the 20th century history of UexkŸllÕs reception in philosophy, we Þnd a number of thinkers disagreeing with UexkŸllÕs claim that the Umwelten of individual humans are closed, but these views are typically framed in each commentatorÕs own vocabulary or viewpoint in such a way that it is di.icult to assess whether they have demonstrated some internal ßaw or inconsistency in UexkŸllÕs thought, or whether they are simply proceeding from di.erent starting points, or engaging in di.erent intellectual projects than the Baltic biologist. As an illustration of this state of a.airs, I focus on a recent collection of essays edited by Kristian Kšchy and Francesca Michelini (2019), representative of the state-of-the-art of scholarship on UexkŸll and his reception within philosophy. The Þrst part of the book deals with the historical context of UexkŸllÕs thought and its inßuence on biological science, while the second focuses on his reception in philosophy. It is the second part which is relevant for this chapter, since it tracks the inßuence of UexkŸllÕs thought on Max Scheler, Helmuth Plessner, Ernst Cassirer, Martin Heidegger, Maurice Merleau-Ponty, Georges Canguilhem and Kurt Goldstein, Gilles Deleuze and FŽlix Guattari, Hans Blumenberg, and Giorgio Agamben. Since the question of whether Umwelten are open or closed crops up throughout these accounts, the volume can function as an overview both of how these philosophers disagreed with UexkŸll on this question and how these disagreements are treated in the current literature. 
Even though the French and German thinkers listed above all consider UexkŸll to be an important thinker and make productive use of his ideas in some way, the philosophers discussed here are united in also rejecting core aspects of UexkŸllÕs thought. The most obvious unifying factor is the rejection of UexkŸllÕs claim that each animalÑincluding each human beingÑlives in a private Umwelt, inaccessible to others. Whether through an appeal to some categorical di.erence between humans and animalsÑa popular route in Germany, often focusing on symbolic cultureÑor through a shift in thinking about subjective experience for all animals, the main task that philosophical readers of UexkŸll have taken on seems to be that of proving him wrong on the point of individual Umwelten. This concern persists today in the Þeld of cognitive science, with Ezequiel Di Paolo calling for a reception of UexkŸll that is not afraid to adapt and change his ideas to suit our own conceptual needs. Like so many philosophers before him, but unlike UexkŸll, he maintains that ÒUmwelten have open horizonsÓ (254). 
Although the essays collected here provide an immense wealth of detail and critical commentary, itÕs not always clear how exactly UexkŸllÕs ideas interact with those of his interlocutors. For the sciences of mind and life yet to come, this much is to be expected. But even for the history of UexkŸllÕs 20th century commentators, itÕs often not entirely clear whether their critiques really engage with the structure of UexkŸllÕs thought or rather evade his conclusions through subtle shifts in the conceptual landscape that allow them to ultimately avoid a direct encounter with his concept of Umwelt. As one example of this problem, consider Hans BlumenbergÕs engagement with UexkŸllÕs thought and its discussion in the secondary literature: 
In his chapter in the book, Cornelius Borck draws attention to UexkŸllÕs inßuence on Hans Blumenberg and traces the critical trajectory of this relationship. Drawing amongst others on UexkŸll and Karl von Baer, ÒBlumenberg develops anthropology as a phenomenological projectÓ and contrasts UexkŸllÕs conception of Umwelt with the notion of a Lifeworld as developed by Husserl and other phenomenologists (Borck 188). Even though Blumenberg ÒridiculesÓ UexkŸll in a chapter of his (1986) Weltzeit und Lebenszeit [Lifetime and Worldtime], he also uses his biological thought, alongside that of Karl von Baer, to pursue Òthe phenomenological project beyond HusserlÕs limitationsÓ (Borck 189). Especially the treatment of time by the two Estonian biologists is fruitful for Blumenberg, and Borck sees an inßuence of the concept of Umwelt even where Blumenberg does not make it explicit. Ultimately, however, Blumenberg concludes that Òthe life-world is no UmweltÓ (Borck 200). 
What is most relevant to us is the point at which Blumenberg parts ways with UexkŸll: He takes on board the basic concept of Umwelt and the idea that Òeach organism lives strictly in its own world-as-perceived and world-as-acted-uponÓ, but makes a special exception for human beings, to whom he ascribes Òthe ability to recognize this speciÞcity and to construct an objective worldÓ (Borck 190). Borck emphasizes UexkŸllÕs notion of the ÒUmwelttunnelÓ, basically an Umwelt extended through time, a sort of four-dimensional extension of the image of the ÒbubbleÓ discussed above (190). Blumenberg rejects this account of Umwelt because Òit contradicts his idea of intersubjectivity as the basis of objectivity and consciousnessÓ (Borck 190). Borck recounts Blumenberg ridiculing UexkŸllÕs conception as a Òbundle of macaroniÓ because Òthe misleading analogy to a tunnel would immediately run into absurdityÓ (192). Unfortunately, Borck does not relay any actual argument from Blumenberg to substantiate this point. It is worth noting that UexkŸllÕs ÒUmwelttunnelÓ bears a striking resemblance to the Òego tunnelÓ which Thomas Metzinger (2009) uses as a central term in scientiÞcally oriented philosophy of mind. Even if the idea seemed ridiculous to a phenomenologically trained German philosopher in the Þrst half of the 20th century, it seems like a serious option for 21st century analytic philosophy of mind. This is an example of a dissatisfying treatment in the secondary literature of a thinker who is positively inßuenced by UexkŸllÕs thought disagreeing with the latterÕs view that the Umwelten on individual humans are closed. It is dissatisfying because we are not in a position to assess either what speciÞc arguments Blumenberg could (or did) muster against UexkŸllÕs view or whether we Þnd those arguments convincing. To be fair, this problem is not unique to the secondary literature but inherited from Blumenberg (and other thinkers, for many parallel cases) himself. 
BlumenbergÕs disagreement with UexkŸllÕs view of closed Umwelten occurs in Worldtime and Lifetime in a section that traces the development of a conception of time as relative to any given biological subject experiencing it, speciÞcally in the thought of Karl Ernst von Baer and UexkŸll. Blumenberg credits von Baer with developing the concept of a subjective time [Subjektszeit] which would condition the appearance of the world to any given subject in accordance with its physiological makeup (Blumenberg 1986: 268). Blumenberg saw this as a biological extension of ProtagorasÕ dictum of the human as the measure of all things, with the added proviso that every other living creature is equally its own measure of all things (ibid.). Whereas he sees von Baer as engaging in Òspeculation about speciÞc measures of time and the conditions of possibility of experience depending on themÓ, he credits UexkŸll with ÒreÞning [this conception] through his distinction between Merkwelt and WirkweltÓ (Blumenberg 1986: 282). The precise structure of a creatureÕs subjective time and its smallest element, the moment, can be studied by experimentally varying the frequency at which a repeated stimulus occurs to determine the precise rate at which it is perceived as continuous, rather than a discreet series of stimulations (see Blumenberg 1986: 283-284). UexkŸll himself applied this technique for measuring the length of a ÔmomentÕ for the scallop (see Blumenberg 1986: 285). 
Where things go wrong, in BlumenbergÕs view, is when UexkŸll applies the same conception of subjective time to humans: ÒThe life of the individual is no longer the one-dimensional chain of impressions, but the three-dimensional tunnel of lifetime, formed by two-dimensional and individually closed discs of Merkwelt.Ó (Blumenberg 1986: 285, my translation). This tunnel is expanded to an Umwelttunnel by including the Wirkmale (roughly: a.ordances) in the picture (ibid.). It is at this point, while describing the consequences of this conception, that Blumenberg draws the comparison to a Òpackage of macaroniÓ which Borck interprets as Blumenberg ridiculing UexkŸll. It is not as clear to me how the tone of this passage should be read, but it is obvious that Blumenberg rejects the consequences of UexkŸllÕs view: ÒWorldtime, conceived as that of the totality of organisms, turns into a system of tubes of lifetimes, that might resemble, say, a package of macaroniÓ (Blumenberg 1986: 285, my translation). It is clear that Blumenberg rejects this, not just because it compromises his titular conception of worldtime, but because he goes on to describe it as a Òformidable degeneration of this initially practicable metaphorÓ (285, my translation). He sees this as the result of UexkŸllÕs Òattempt to assign its own world to each organismÓ and traces its failure back to the fact that UexkŸll was writing what appears like a work of phenomenology in 1922 without availing himself to the Òachievements and disappointmentsÓ of phenomenological philosophy (285, my translation). What is crucial here for us is that Blumenberg jumps straight to an explanation of why UexkŸll made the mistake of describing human Umwelten as private and closed, without Þrst establishing that this is indeed a mistake. The mere fact that it conßicts with BlumenbergÕs own view cannot establish this. It is important to be clear here about what I am claiming and why it matters: I am not claiming that there are no possible arguments against UexkŸllÕs view that p-Umwelten are private. Nor am I claiming that anyone who holds a view di.erent from UexkŸllÕs has a burden of demonstrating that UexkŸllÕs view is wrong. However, I am claiming that someone who directly asserts that UexkŸllÕs view is wrong thereby acquires the burden of substantiating this assertion with arguments, and that Blumenberg does not su.iciently do so. Secondarily, and more importantly for this project, Borck does not raise the question of whether BlumenbergÕs criticism of UexkŸllÕs views on the closedness of Umwelt stands on solid footing. This shows that the question of whether Umwelt is open or closed is not given su.icient attention in the current literature, reinforcing the need for an analysis of the kind I provide below. 
Of course, Blumenberg is just one example, but this case illustrates a wider problem in the philosophical responses to UexkŸll and the current state of secondary literature on it, speciÞcally in relation to the question of whether human Umwelten are open or closed. In the rest of this section, I show that this problem also persists in recent scholarly work that deals with UexkŸllÕs own thought, rather than his reception by 20th century philosophers. One of the few 21st century monographs devoted to UexkŸllÕs thought is Brett BuchananÕs (2008) Onto-Ethologies: The Animal Environments of UexkŸll, Heidegger, Merleau-Ponty, and Deleuze. It describes the question of openness and closure like this: 
ÒThe biological world of animals and their environments consists of an artful play of interconnections, to the degree that one organism is necessary for understanding an other. The Umwelten of organisms are therefore not simply closed spheres, as if locking the organism within a self-concealed and isolated container. The animal is not an object or entity, but a symphony underscored by rhythms and melodies reaching outward for greater accompaniment. Individual Umwelten are necessarily enmeshed with one another through a variety of relationships that create a harmonious whole.Ó (Buchanan 2008: 28). 
Buchanan claims that UexkŸll conceives of Umwelten not as strictly separated, self-contained worlds, but as intersecting, interlocking, and enmeshed. What we see play out here is a contrast between two di.erent metaphors employed by UexkŸll throughout his writing, Òthat of the soap bubble and the musical compositionÓ (Buchanan 28). On BuchananÕs reading, the image of the soap bubble constructs Umwelten as closed, private, isolated worlds of experience, but the metaphor of nature as a musical composition emphasizes that Umwelten are open towards each other and necessarily connected. This is the case because Òthe interrelations in terms of Ôcounterpoint,Õ Ôduets,Õ and Ôharmonies,ÕÓ which UexkŸll identiÞes in the grand symphony of nature all require at least two elements (Buchanan 29). No single Umwelt can exist by itself because the structure of the natural world is essentially relational, and because UexkŸllÕs thought Òemphasizes the need for at least two tones to create a meaningful pictureÓ, Òit is clear that an intersubjective model is at its centerÓ (Buchanan 29, 28-29). 
This assessment of UexkŸllÕs concept of Umwelt is incorrect, as UexkŸll repeatedly makes it clear that Umwelten are closed. At the end of Umwelt und Innenwelt der Tiere, the Þrst monograph in which he presents the concept, UexkŸll lists a set of rules for biologists in which he makes this explicit: 
Ò1. Every creature constitutes the center of its Umwelt, which it encounters as an autonomous subject [...]. 
3. In the Umwelt of each animal, there exist only things which belong exclusively to this animal. 
14. 
The observer can only perceive the features acting on the animal as traits of his own world of appearances. The sensations of the animal remain forever hidden to him. 

15. 
Every animal carries its Umwelt around with it for all its life like an impenetrable shell. 

16. 
The same is true of the observerÕs world of appearances, which closes him o. completely from the universe, since it constitutes his Umwelt. 


19. The world of appearances of each human being likewise resembles a hard shell, which constantly encloses them from birth until death.Ó (von UexkŸll 2014[1921]: 236.237, my translation) 
From this list of core tenets, it is clear that UexkŸll considers the Umwelten of both human and non-human individuals to be closed. Then where does BuchananÕs claim that UexkŸllÕs Umwelten are Ònecessarily enmeshed with one anotherÓ, i.e. open, originate? It is based in BuchananÕs interpretation of UexkŸllÕs view of Nature as a musical symphony. Besides the account of individual living subjects inspired by Kant, UexkŸll also developed a holistic view of nature as a meaningful totality that was strongly inßuenced by Goethe. Based on a musical metaphor, he developed a vision of nature as a grand meaningful whole consisting of melodies, harmonies, and counterpoints between the morphologies and behaviors of, say, predator and prey. This view has clear overtones of Romanticism, organicism, and even pantheism. It is this musical metaphor that Buchanan draws on for his reading of Umwelt as open. However, his take on the issue seems overly optimistic and paints UexkŸll in a far more liberal light than is plausible given his biography: 
Ò[T]o say that natureÕs plan is similar to a musical composition can conjure up many images of nature: is it a Vivaldian plan, with plenty of baroque orchestration? Or is nature more comparable to SchšnbergÕs minimalist twelve-tone pieces? Or the o.-tempered plays of a John Coltrane score? [É] More than likely, UexkŸll would respond that natureÕs compositional plan includes all of these scores, and many more.Ó (Buchanan: 27) 
UexkŸllÕs vision of a compositional plan of nature did not include improvisation, modernism, or innovation. Instead, his conception was staunchly static and conservative. When he extended his 
account of Nature into a view of human social and political order (itself a deeply reactionary maneuver), he used the idea of a symphony to oppose equality, which according to him would ultimately result in the Òempty clanging of bellsÓ (Mildenberger & Herrmann 2014: 295-296). UexkŸll was not thinking of music in general, but envisioned one single symphony of Nature. He wrote of the biological world as organized according to a single unchanging Plan, not according to multiple plans, possibly changing and interacting. UexkŸll used the musical metaphor to describe how an individual animal stands in a Òcontrapuntal relationÓ to its Umwelt and how di.erent animals and their behaviors together form a harmonious whole, but this does not imply that their Umwelten are open, nor does UexkŸll claim this (UexkŸll 2010: 171). The importance of BuchananÕs misreading lies not just in the false impression that UexkŸllÕs account describes Umwelten as open, but it also shows that in order to get a reliable grasp on the question, we have to pay more attention to the di.erent senses of Umwelt and the corresponding criteria for openness or closure that go along with them. 

4.3 Five di.erent claims and what they entail 
The question of whether human Umwelten are open or closed has been the central point at which philosophical commentators disagree with UexkŸll throughout the 20th century, and it is still a core concern today both in UexkŸll studies and for those researchers who seek to make use of Umwelt for their own project. Given this centrality, it is peculiar that so far no dedicated discussion has taken place of what it would mean for Umwelt to be open or closed. The ways in which individual thinkers disagreed with UexkŸll have been noted, but as of yet there has been no systematic discussion of what is at stake in these agreements that would allow us to compare and evaluate di.erent claims. This section will provide such a discussion and categorize Þve possible positions that can be occupied in the debates about the openness or closure of Umwelt. The motivation for this course of action is the following: Before we can try to answer the question of whether Umwelt is open or closed, we have to clarify the meaning of the question. As it turns out, we are really dealing not with one question, but with several di.erent questions that appear as one, because they all use the word Umwelt to designate a variety of concepts. As I have already shown, UexkŸll himself uses Umwelt in two di.erent senses. In the following, I will demonstrate that what it means for Umwelt to be open or closed also di.ers between these two senses. Ideally, we would then hope to Þnd claims in the literature that can be categorized as pertaining to one of these two senses of Umwelt. Unfortunately, this is not always the case, since many authors use Umwelt in a sense that is either vague and thus cannot be clearly categorized as referring to p-Umwelt or e-Umwelt, or they use Umwelt in a precise but idiosyncratic way. The views that have been expressed by UexkŸll and his commentators can therefore be categorized as instances of Þve di.erent claims: e-Umwelt is open, e-Umwelt, is closed, p-Umwelt, is open, p-Umwelt, is closed, and Þnally claims that Umwelt is open, where Umwelt is used in some other sense. In principle, it is possible for someone to express a sixth version, where Umwelt is closed according to some idiosyncratic meaning of Umwelt, but none of the prominent commentators on UexkŸll holds such a view. This also means that the categorization I propose here cannot by itself once and for all solve the question of whether Umwelt is open or closed. This is so because the view that some idiosyncratic sense of Umwelt is open can only be evaluated within the speciÞc conceptual system in which it is enunciated. Evaluating e.g. DeleuzeÕs view that Umwelt is open would then require a separate work of Deleuze-scholarship, and so on. What my categorization can deliver is a method for assessing those claims that more directly line up with the two ways in which UexkŸll used the term Umwelt, and also a characterization of the kind of claim that a thinker would have to make, and the sorts of arguments that might support it, in order to substantially disagree with UexkŸllÕs own views about the closure of 
Umwelt. 
What it means for Umwelt to be open or closed di.ers between the two senses of the word. As it turns out, UexkŸll thought that both e-Umwelt and p-Umwelt are closed, but for di.erent reasons. When we say that e-Umwelt is closed, we are talking about a set of behaviors and the a.ordances of which they make use: Òeverything a subject perceives belongs to its perception world [Merkwelt], and everything it produces, to its e.ect world [Wirkwelt]. These two worlds, of perception and production of e.ects, form one closed unit, the environment [Umwelt]Ó (von UexkŸll 2010[1934]: 42). The perception world and e.ect world are linked to the subject through functional cycles. These are schemata of di.erent meaningful behaviors and they get executed whenever the subject both feels the corresponding need and perceives the a.ordances that allow it to satisfy it. Every functional cycle is a closed loopÑfrom start to Þnish of this action sequence it gets executed by itself, without relying on any other activities. Additionally, each animal subject has only a Þxed and limited number of functional cycles in its behavioral repertoire, according to its Bauplan. These points are fundamental enough that they are reßected in UexkŸllÕs Ôfundamental tenets of biologyÕ discussed above: 
Ò10. As soon as their activity starts, the functional cycles form a mechanism closed in on itself [É]. 
12. The Umwelt is only indexed fully when all functional cycles (of the medium, the prey, the enemy, and the sexes) have been circumscribed.Ó (von UexkŸll 2014[1921]: 236, my translation) 
What it means for e-Umwelt to be closed is thus for each living subject to be stuck with a Þxed and static set of functional cycles which are pre-determined by the grand Plan of Nature. Depending on which time scales we include in the claim of closure, the view becomes more extreme and less plausible: clearly animals acquire new behavioral capacities during their lifetimes through learning and development. Presumably, UexkŸll might account for this by arguing that these processes aim at a set of functional cycles that is already pre-determined by the Plan. The plasticity that enables learning and development would then only provide a limited kind of openness to e-Umwelt at the scale of the individual subject and its lifecycle. It is tempting to treat UexkŸllÕs vision of the parts of Nature as determined by a larger Plan as a direct solution to the problem created by his Òanti-DarwinismÓ: Since he rejected DarwinÕs account of species change and adaptation, UexkŸll needed an alternative account of why the parts of nature seem to Þt together so perfectly. However, this reading is a little too simple, since UexkŸll did not reject the claim that new species emerge, but only the view that this happens in a strictly gradual manner (von UexkŸll 1913: 17-19). He ascribed to Darwin the view that ÒNatura non facit saltusÓ, which he considered as having been disproven (17, 18). In light of these arguments, UexkŸll would seem to endorse the view that new species emerge (perhaps in an event similar to the notion of Òpunctuated equilibriumÓ) and with each new species, a new kind of Umwelt opens up to its members. The emphasis on the static character of a large network of meaningful relations between the parts of nested ecological systems should perhaps not be read as a (weak) attempt at historical explanation but as a methodological commitment to a synchronic rather than a diachronic analysis, akin to HerediaÕs reading of UexkŸllÕs method as a Òstructural vitalismÓ (Heredia 19). From this perspective, the closure of e-Umwelt could be interpreted both as an empirical claim about individual animals and as a methodological description of the end point towards which the study of a speciÞc animal is directed, at which Òall functional cycles (of the medium, the prey, the enemy, and the sexes) have been circumscribedÓ (von UexkŸll 2014[1921]: 236). This also gives us a clear interpretation of what it means to say that e-Umwelt is open rather than closed: e-Umwelt is open at various scales to processes which change the behavioral repertoire of a subject and increase or diminish the range of a.ordances that it can perceive and act upon. 
The meaning of openness and closure for the phenomenal Umwelt is quite di.erent. For UexkŸll, the p-Umwelt of each individual subject is closed because each individual subject constructs its own Umwelt. As discussed in chapter 2, UexkŸll conceives of his conception of Umwelt as an extension of KantÕs account of human subjectivity, in which the conditions of the possibility of our experience are grounded in our physiology. While he shares KantÕs emphasis on the importance of time and space as the fundamental dimensions of experience, UexkŸll traces the origin of these forms of sensibility to the sensory organs and nervous systems of embodied subjects. The meaningful contents of our experience, such as the objects we perceive, are explained not as the result of a process of judgement that brings intuitions under concepts, but as the result of a constructive process which translates the stimulations of sensory organs into basic signs, which in turn are combined into more complex meaningful compounds and transposed outwards into the subjective space of the individualÕs p-Umwelt. 
Because each individualÕs nervous system creates an Umwelt, a Ònew world arises in each bubbleÓ, and there are Òas many worlds as there are subjectsÓ (von UexkŸll 2010[1934]: 43, von UexkŸll 1926: 70). What it means for these p-Umwelten to be closed is that each individual can only ever experience their own p-Umwelt, never that belonging to another subject, and, conversely, no other subject can ever experience theirs. In this sense, p-Umwelten are necessarily closed, each individual has one and it is fundamentally private, inaccessible from the outside and to anyone else. This follows from UexkŸllÕs account of the construction of p-Umwelt as the domain of subjective experience, but it also seems to follow from basic facts about how we use the word ÔexperienceÕ. Whenever I experience something, the occurrent experience is mine. It is not clear even on the linguistic level what it would mean to have someone elseÕs experience. However, it is also true that we also commonly talk of Ôshared experiencesÕ. Claims that p-Umwelten are open proceed from this notion, but they must elaborate it in ways that are metaphysically demanding, as I outline below and then in more detail in chapter 6. 
Based on the foregoing analysis, we are left with Þve di.erent claims about the openness or closure of Umwelt that should be distinguished when considering their relationship to UexkŸllÕs thought: 
Claim 1: e-Umwelt is closed. 
Saying that the e-Umwelt of a subject is closed is claiming that its behaviors can be captured by a Þnite set of functional circles, where each functional circle in turn is also closed. What it means for 
a functional circle to be closed is that capacities of the organism that connect to opportunities in its environment are speciÞable for each functional circle and form a complete functional and meaningful whole. Since the e-Umwelt, and the functional circles that form its conceptual core, are methodological tools of the biologist studying animal behavior, we can helpfully think of this closure as a methodological feature that is related to abstraction. 
We may talk about the Umwelt of the sea urchin, using the singular in a generic function to mean all or any sea urchins. Even though the empirical study of the sea urchin involves observation and experimentation on a Þnite number of distinct individuals, the goal of the study is not to gain knowledge about these speciÞc individuals, but about sea urchins in general. We abstract away from individual di.erences to construct an image or conception of the sea urchin, in the generic singular. This is possible because all individual sea urchins share features that allow us to treat them as instances of a single species, and to describe this species while abstracting from the di.erences between individuals. Part of this method of abstraction is the description of functional cycles and their complete enumeration into an account of the sea urchinÕs e-Umwelt. The closure of this e-Umwelt is tightly bound to these methodological features and the aims of the speciÞc research project: We can treat the functional cycles available to an average adult sea urchin as a Þxed set, based on the outcome of our empirical study, if we are interested only in the average adult sea urchin. This is the sense in which we can say that UexkŸll considers the e-Umwelt of an animal to be closed. 
In contrast, a developmental study of the time in its life at which each functional circle becomes available to the individual cannot abstract away from this change over time. UexkŸll himself might well have justiÞed privileging the set of functional cycles that the average, uninjured adult sea urchin possesses by arguing that it constitutes the goal of all prior developmental stages, and the goal of health towards which a sick or injured organism works in its e.orts at self-regeneration. With Heredia and Foucault, we can also think about UexkŸllÕs emphasis on Òsynchronic totalitiesÓ instead of Òdiachronic and genetic schemasÓ as an instance of the broader shift from the 19th century Òpredominance of time and historyÓ towards the 20th century preoccupation with Òstructures, forms, [and] systemsÓ (Heredia 2019: 18, 17, 17). 
Claim 2: e-Umwelt is open. 
Claiming that e-Umwelt is open involves asserting that the behavior of an animal is not Þxed by a Þnite set of functional circles or cannot usefully be understood in this way within a particular 
explanatory project. The crucial part here is to note that the openness or closure of e-Umwelt depends on the speciÞc explanatory project that one is engaged in. Whereas for UexkŸll, Ò[t]he emphasis [É] was not, however, upon the development of the organism [É] but upon its being,Ó other researchers have applied his notion of Umwelt to discuss developmental questions, e.g. observing that Òearly development is a period of rapid expansion in the complexity of the developing UmweltÓ (Cassirer 1969: 199Ð200, quoted in Brentari 2015: 189, Schank et al. 2023: 105349). It would be unhelpful to argue that Schank et al. are misusing the concept of Umwelt in their developmental analysis. It seems more helpful to recognize that they are involved in a di.erent project, which di.ers in its basic approach from UexkŸllÕs Òproject of structural biologyÓ (Heredia 2019: 19). 
A particularly relevant example of an account of e-Umwelt as open can be found in Edward Baggs and Anthony Chemero (2021), who Òadopt a historicalÐdevelopmental perspectiveÓ to show that the Umwelten of humans are open (Baggs & Chemero 2021: 2187). Their examples include VygotskyÕs account of how an infant learns to point at objects from their caretakerÕs response to failed attempts at grasping and also Òthe history of an individualÕs coupling to the environmentÓ throughout their life, including individual facts such as Òthat she learned to read Japanese kanji, to play bass, to do tricks on a skateboardÓ (Baggs & Chemero 2021: 2186). What it means to claim that the e-Umwelt of an individual is open is that Ò[t]o the extent that we are able to learn throughout our life, the umwelt never constitutes a limit on our experience, but is merely a label for the subset of our surroundings that we are currently oriented towardsÓ (Baggs & Chemero 2021: 2187). An extended analysis of their view is included in chapter 5. 
On this basis, we also have to evaluate the relationship between claims 1 and 2: Even though on the face of it the two claims seem to be mutually incompatible opposites, considering the methodological sca.olding within which these claims are made allows us to conceive of them as belonging to di.erent explanatory projects. These projects might be rivals, or they might be complementary. What this means is that a substantial criticism of UexkŸllÕs claim that e-Umwelt is closed should address his methodological commitments, rather than simply showing that e-Umwelt is open if a di.erent approach or perspective is adopted. While it is true that e-Umwelt is open once development is considered, this in itself is not a critique of UexkŸllÕs decision to focus on structures of meaningful behavior instead of morphological development. Confronting UexkŸllÕs claim that e-Umwelt is closed requires a methodological engagement with his ethology, and in turn produces claims and arguments about how ethological research and theorizing should proceed. 
Claim 3: p-Umwelt is closed. 
To say that p-Umwelt is closed is to say that each individual living subject only ever experiences their own experiences and never those of another subject. While it sounds awkward to Òexperience an experienceÓ, it would not help to talk about Òaccessing an experienceÓ, since this suggests that there is an experience and, in addition to it, the act of accessing it. This would be misleading, since having an experience is the only way to engage with it directly and, conversely, to be had is the only way for an experience to ÔbeÕ. What it is for an experience to be experienced, and what it is to access an experience, is to have (or experience) it. The word ÔexperienceÕ here refers to phenomenal experience (sometimes called Ôsubjective experienceÕ) as we experience it at the time when it happens. A very di.erent use of ÔexperienceÕ would be to talk e.g. about the experience of growing up in the American Midwest in the 1990s. This is an experience that is shared by many and can be access in recollection, or even in a sense accessed by people who never had this experience themselves e.g. by reading about it. Importantly, this is a very di.erent kind of experience that is not at issue here. If p-Umwelten are closed, each experience belongs to one and only one subject. While it is not clear what it would mean for an experience to be had by no one, this question is less important for thinking about p-Umwelt. More crucially, if all p-Umwelten are always closed, there is no single (token) experience that is shared between two di.erent subjects. If there were, this shared experience would be part of both of their p-Umwelten, and they would not be closed. 
UexkŸll holds this view early on, already in his 1902 Im Kampfe um die Tierseele [Battle over the AnimalÕs Soul], he states that Òknowledge of anotherÕs soul is permanently closed o. to us, since there is no direct tra.ic from soul to soulÓ (von UexkŸll 1902: 19). The closure of p-Umwelt forms a central part of the methodological strictures outlined at the end of his 1909 Umwelt und Innenwelt der Tiere [Umwelt and inner world of animals]: ÒIn the Umwelt of each animal, there only exist things which belong exclusively to this animalÓ, the Òsensations of the animal remain forever hidden toÓ the observer, and likewise the Òsame is true of the observerÕs world of appearances, which closes him o. completely from the universe, since it constitutes his UmweltÓ (von UexkŸll 2014[1921]: 236-237, my translation). Late in his career, in 1936, it is also expressed in the title of his biographical writings on the lives of his friends, Nie geschaute Welten [Worlds never seen], rea.irming that this closure pertains to human p-Umwelten as much as those of other animals. 
Claim 4: p-Umwelt is open. 
To say that p-Umwelten are open (or intersect, or enmeshed, or are porous) is to claim that at least sometimes experiences are shared between two or more living subjects in a strong sense. What I mean by sharing experience in a strong sense is that it is not enough for two subjects to have qualitatively identical experiences at the same time. In UexkŸllÕs poetic Þgure or speech, we could think of their p-Umwelten as two soap bubbles that shimmer in exactly the same colors, but exist separately from each other, side by side, and closed. What is required for strong sharing of an experience is that two separate subjects partake in, or have, one single token experience, together. For our discussion, two aspects are relevant: First, to claim that p-Umwelt is open creates the challenge of specifying what exactly is means for two subjects to share a single experience, how that is possible, and how we could know whether this actually occurs. I remain neutral here about who should shoulder the burden of facing this challenge, but will attempt to do some work towards it in chapter 6. Second, in order for the claim that p-Umwelt is open to constitute a repudiation of UexkŸllÕs claim that p-Umwelt is closed, it is not enough to show that the former claim is intelligible, plausible, and attractive, it must also be shown that it is (in some important way) preferable to the latter. This, too, will be taken up in chapter 6. 
The most relevant example for the claim that p-Umwelt is open, and the primary target of my discussion in chapter 6, is the enactive view of intersubjectivity developed by Thomas Fuchs and Hanne De Jaegher (2009). They build on the phenomenological distinction between two concepts of bodyÑLeib and Kšrper or lived body and living bodyÑdeveloped by Edmund Husserl and expanded by Merleau-Ponty, to argue that intersubjectivity involves Òmutual incorporation, i.e. a process in which the lived bodies of both participants extend and form a common intercorporalityÓ (465). I interpret this to mean that experience is shared in the strong sense, indicated among other things by the singular expression Òa common intercorporalityÓ. The lived body in phenomenology is both oneÕs own body as experienced by oneself and a more general aspect of how one relates to the world in subjective phenomenal experience, so oneÕs lived body is both a part of and a more general characteristic or structuring factor of oneÕs p-Umwelt. If two lived bodies are extending to form one single ÒintercorporalityÓ, this seems to imply that there is at least one entity that is a part of two distinct p-Umwelten belonging to the two subjects sharing the intersubjective episode. Chapter 6 will provide a more comprehensive argument for my reading of Fuchs and De JaegherÕs position, question whether phenomenology alone can provide us with su.icient support for this view, and suggest an alternative account of intersubjective experience that can do without strong sharing. 
Claim 5: humans do not inhabit closed Umwelten, but the world they inhabit is neither an e-Umwelt nor a p-Umwelt. 
The last option is to claim that humans do not inhabit closed Umwelten, but without claiming that either their e-Umwelten or their p-Umwelten is open. This could take the form of either claiming that humans just do not have Umwelten, or using the term Umwelt with a di.erent meaning, distinct from either e-Umwelten or p-Umwelten. In either case, the most immediately useful way to make this claim would include a direct argument for why UexkŸll is wrong and humans do not inhabit closed Umwelten. In practice, this claim most often follows from an incompatibility between UexkŸllÕs notion of closed human Umwelten and the larger system of thought or perspective that another thinker is developing. This makes it di.icult to adjudicate such disagreements, since it seems to require assessing the entire separate philosophical oeuvre and/or bringing it into conceptual contact with UexkŸllÕs thought in a systematic way. 
Two examples of these two versions are found in Heidegger and Deleuze, respectively. Even though Heidegger takes UexkŸllÕs theoretical biology from which to distinguish the relationship between human and world from the situation of other animals and inanimate objects, he eventually draws the applicability of the term Umwelt into question not just for humans, but also for animals (see Brentari 2015: 199-200). He maintains that Ò[s]ince J. v. Uexku.ll we have all become accustomed to talking about the environmental world [Umwelt] of the animal. Our thesis, on the other hand, asserts that the animal is poor in worldÓ (Heidegger 1995: 192, cited in Brentari 2015: 199). Consequentially, he also refers to the Òso-called environmentÓ of animals and builds on UexkŸllÕs notion of the functional circle to develop his own concept of the Òdisinhibiting ring (Enthemmungsring)Ó (Brentari 2015: 199). Despite his qualms about the term Umwelt, Heidegger adopts a view of the worlds of animals as closed, such that Òthroughout the course of its life the animal is conÞned to its environmental world, immured as it were within a Þxed sphere that is incapable of further expansion or contractionÓ (Heidegger 1995: 198, cited in Brentari 2015: 201). In a move common to readers of UexkŸll in both 20th and 21st centuries, Heidegger occasionally misinterprets UexkŸll to make him appear in agreement with HeideggerÕs own views: ÒIt is true that amongst the biologists Uexku.
ll is the one who has repeatedly pointed out with the greatest emphasis that what the animal stands in relation to is given for it in a 
di.erent way than it is for the human beingÓ (Heidegger 1995: 263-264, quoted in Brentari 2015: 200). It is not UexkŸll, but only Heidegger, who concludes that Òthe animal is separated from man by an abyssÓ, precisely because of the categorical di.erence between the kinds of worlds they inhabit (Heidegger 1995: 263Ð264, quoted in Brentari 2015: 200). 
In his Spinoza: Practical Philosophy Deleuze, as mentioned above, argues that Spinozist ethics have Ònothing to do with a moralityÓ, but constitute an ethology (1988: 125). This view is developed by reading Spinoza through UexkŸll and reading UexkŸll through Spinoza. As he had done together with Guattari in A Thousand Plateaus (2009), Deleuze picks up both on UexkŸllÕs account of Umwelt and on his musical metaphor of ecological relations: ÒEvery point has its counterpoints: the plant and the rain, the spider and the ßy. So an animal, a thing, is never separable from its relations with the worldÓ (1988: 125). However, Deleuze diverges signiÞcantly from UexkŸllÕs thought, even while appearing to give an account of it, which becomes clear when he contrasts a Ôtranscendent planÕ with a Ôplane of immanenceÕ. A transcendent plan gives genetic and structural guidance to the development of forms from the outside, such as Òa design in the mind of a god, but also an evolution in the supposed depths of nature, or a societyÕs organization of powerÓ (1988: 128). In contrast, a plane of immanence is a Òprocess of compositionÓ that we perceive directly in Òthat which it makes perceptible to usÓ (ibid.). However, where Deleuze champions the plane of immanence, UexkŸllÕs conception of the Bauplan is far more closely aligned with the transcendent plan. Deleuze writes that Goethe is not really a Spinozist because he Ònever ceased to link the plan to the organization of a Form and to the formation of a SubjectÓ (1988: 129-130). This is inconsistent with DeleuzeÕs reading of UexkŸll as a Spinozist, since he follows Goethe in all these points and even explicitly describes Nature as an obscure higher entity forever hidden beyond the appearances we inhabit but structuring them according to its plan, a prime example of the kind of transcendental plan that Deleuze rejects. Even more important for my discussion, and the topic of subjective experience, is DeleuzeÕs move away from individual subjects towards a single plane of immanence, on which Ò[t]here is no longer a subject, but only individuating a.ective states of an anonymous forceÓ (1988: 128). This is directly opposed to the core of UexkŸllÕs thought, despite DeleuzeÕs presentation of UexkŸll as a fellow Spinozist. 
For the present study, both HeideggerÕs and DeleuzeÕs reading of UexkŸll create an impasse. It would require substantial e.orts in Heidegger scholarship and Deleuze scholarship to demonstrate that their disagreement with the claim that human Umwelten are closed is wrong either on their own terms or on some neutral conceptual ground we could reasonably expect them to share with us (and UexkŸll). This goes beyond the scope of my investigation, but at minimum the preceding remarks should establish that merely noting that Heidegger or Deleuze disagreed with UexkŸll is not su.icient to show that UexkŸll was wrong. The fact that both Heidegger and Deleuze are demonstrably unfaithful or inaccurate in characterizing UexkŸllÕs thought when they outline their own relationship to it should be enough to make us wary of taking their conclusions at face value. Conversely, however, the fact that a thinker uses the term Umwelt in an idiosyncratic way that is detached from UexkŸllÕs thought does not invalidate this new use. Whether this new use achieves its philosophical goals would have to be assessed in terms appropriate to the speciÞc thinkerÕs project and methodology. 

4.5 SigniÞcance going forward 
In this chapter, we have seen that the question of whether the Umwelten of humans are open or closed has occupied many of UexkŸllÕs most important philosophical readers. Despite their di.erent systems of thought, they seem to be almost unanimously united in opposition to UexkŸllÕs claim that the Umwelt of each human individual, just like that of any living subject, is inescapably closed o. and private. Although this is one of the most central thematic threads running through the reception of UexkŸllÕs thought, the question of openness and closure as such has not been thematized in the secondary literature. Individual discussions of UexkŸllÕs philosophical readers in the secondary literature often reproduce the weaknesses of the interpretations they discuss: the word Umwelt is taken out of its conceptual context in UexkŸllÕs work and made to perform in new ways that often fail to connect directly to the way UexkŸll used it. Especially the crucial distinction between an ethological and a phenomenological sense in which the term ÔUmweltÕ is deployedÑby a scientist studying another subject from the outside, or by an imaginative observer attempting to envision what it would be like from the inside to inhabit another UmweltÑis crucial for the question of openness and closure in a way that has so far not been appreciated. Using this distinction, we can see that openness and closure each have two distinct meanings, depending on whether we are talking about e-Umwelt or p-Umwelt. Additionally, there are other potential meanings that ÔopennessÕ and ÔclosureÕ can have when the term ÔUmweltÕ is used in other ways entirely. 
The problem of whether p-Umwelt is open or closed is linked tightly to the philosophical issue of subjective experience in general. How these debates play out in continental philosophy is of particular interest for the philosophy of embodied cognition, because it shares key goals with many continental thinkers and has drawn on their work from its inception. Merleau-PontyÕs work has been at the heart of embodied cognition, HeideggerÕs thought has been inßuential (with some caveats), and new sources of conceptual innovation are still being developed (two current examples being Gilbert Simondon and Helmuth Plessner). However, this kind of integration between continental philosophy and philosophy of cognitive science brings special di.iculties with it. 
The reception of the concept of Umwelt can teach us useful lessons here: compared to late Merleau-Ponty, Deleuze, or Heidegger, UexkŸll is easy to understand, and yet his reception has largely failed to appreciate the crucial distinction between two senses of Umwelt. The conceptual di.iculties and dangers when working with heavy-duty continental theory are likely greater than the challenges of reading UexkŸll, and more explicit methodological reßection about how to deal with these challenges in the philosophy of embodied cognitive science would be very valuable. The question of whether Umwelten are open or closed is a good way to illustrate these di.iculties: It might be possible to demonstrate the openness of p-Umwelt by drawing on the more metaphysically weighty aspects of thinkers like Merleau-Ponty, Deleuze, or Heidegger, but in its reception of continental philosophy, the philosophy of cognitive science has often, and for good reason, prioritized those aspects of their work which can be most readily used to design and conduct experiments, or inform scientiÞc modelsÑwhich is to say their least metaphysically laden views or concepts. 
For the philosophical and scientiÞc discussion of Umwelt, this chapter has provided a systematic way to interpret di.erent kinds of claims about openness and closure. This makes it possible to more accurately assess those positions in the literature that disagree with UexkŸllÕs claim that the Umwelten of individual humans are closed. At this point, we can at least conclude that the history of UexkŸllÕs reception in 20th century French and German philosophy has not clearly demonstrated that his position is wrong. We can thus treat this issue as a live question going forward. The next two chapters will apply the distinctions developed so far to the reception of the term ÔUmweltÕ in cognitive science, with a special focus on debates within embodied cognition, and to discussions of intersubjectivity that do not always explicitly refer to Umwelt, but concern the same fundamental issue and to which the distinction between e-Umwelt and p-Umwelt and the resulting criteria for openness and closure can be applied fruitfully. 
Chapter 5: Umwelt in Cognitive Science 
5.1 Three kinds of reception 
In the preceding chapters, we have established that there are two di.erent senses of Umwelt, and how the di.erence between the two is related to the topic of subjective experience. In this chapter, I apply this distinction to existing discussions about Umwelt in the philosophy of cognitive science. I focus on three kinds of UexkŸllÕs reception in the philosophy of cognitive science in light of the distinction between e-Umwelt and p-Umwelt. First, I will show that two of the most prominent philosophers of cognitive science, Andy Clark and Daniel Dennett, have cited UexkŸllÕs concept of Umwelt as if it were agnostic about subjective experience. While using the concept in this way could be useful, doing so without pointing out that this is diametrically opposed to how UexkŸll created this concept runs the risk of hindering the general reception of UexkŸllÕs thought. Conversely, readers who already know that the concept Umwelt normally concerns subjective experience may misinterpret this other way in which it is used in the philosophy of cognitive science. These misconceptions are especially important because Umwelt is being used in debates that concern subjective experience and since, as my overall project shows, it is crucial for writers and readers to be clear on which sense of Umwelt is being used at any given time in these debates. Next, I evaluate Ed Baggs and Anthony ChemeroÕs proposal to use Umwelt as a bridge between ecological psychology and enactivism. I argue that the concept of Umwelt, while it resolves debates within ecological psychology about the di.erences between species-level and individual-level descriptions, does not bridge the gap between the position of an external observer studying an organism (such as an ecological psychologist) and the subjective experience this organism is having (which one can study using the phenomenological method, as enactivists endorse). Finally, I discuss a competing view within ecological psychology that rejects the concept of Umwelt and instead proposes to adopt UexkŸllÕs musical metaphors about the harmony of the natural world. I argue that the reasons for rejecting Umwelt fail to take into account the di.erence between e-Umwelt and p-Umwelt and draw into question the utility of UexkŸllÕs musical metaphors for cognitive science. The upshot of these three discussions is that Umwelt can be a useful concept for cognitive science, but only if we pay attention to the di.erence between e-Umwelt and p-Umwelt. Neglecting this distinction can lead to either rejecting Umwelt altogether based on ßawed reasoning, or overestimating the degree to which Umwelt can help integrate di.erent perspectives. 

5.2 Umwelt without experience 
The inßuence of UexkŸllÕs thought on cognitive science reaches back into its prehistory, with the founder of general systems science Ludwig von Bertalan.y citing UexkŸllÕs work on the Òreßex republicÓ of the sea urchin (Bertalan.y 1937: 53, cited in Kšchy 2022). However, more signiÞcant uptake of UexkŸllÕs thought and especially the concept of Umwelt has increased since the early 1990s alongside the rise of embodied cognition (see Yazõcõ 2018). Rodney Brooks used UexkŸllÕs notion of Merkwelt in his (1986) memo ÒAchieving artiÞcial intelligence through building robotsÓ and argued that Òeach animal species, and clearly each robot species with their own distinctly non-human sensor suites, will have their own di.erent MerkweltÓ (4). BrooksÕ work was central for the development of embodied cognition, and it is possible that his use of Merkwelt to describe both animals and robots regardless of whether the latter have subjective experience set the stage for treating the term Umwelt in the same way. Whether or not BrooksÕ UexkŸll-reception inßuenced this, the 1990s and the 21st century would see two of the most famous philosophers of cognitive science, Andy Clark and Daniel Dennett, use Umwelt in a way that is completely decoupled from the question of subjective experience. In this section I will discuss how Clark and Dennett use the term Umwelt and highlight how their usage di.ers from UexkŸllÕs. 
Within the Þeld of embodied cognition, one of the most widely read texts in which readers may encounter a brief description of UexkŸllÕs Umwelt is Andy ClarkÕs Being There: Putting Brain, Body, and World Together Again (1997). Clark introduces Umwelt as a conceptual precursor to Òniche-dependent sensingÓ in robotics and deÞnes it as Òthe set of environmental features to which a given type of animal is sensitizedÓ (Clark 1997: 24). His explanation of the concept is short and centers on a citation of UexkŸllÕs popular passage on the tick. From ClarkÕs description, it is not clear whether an Umwelt involves experience or not, but he embeds it in a larger account of a robot called Herbert and concludes that the Òsimilarity between the operational worlds of Herbert and the tick is strikingÓ (25). This makes it at least possible to understand Umwelt as unconcerned with experience from ClarkÕs account, but whether other authors who suggest that robots have Umwelten were directly inßuenced by Clark cannot be established. Clark himself, at least, clearly believes that Umwelt without experience is possible, more than two decades after Being There: ÒA simple robot could [É] properly be assigned an Umwelt. But the simple a.ordance-sensitive robot need not thereby experience any world at allÓ (Clark 2019: 284). This is in contrast to UexkŸll, for whom having an Umwelt necessarily involves experiencing it. 
Members of the general philosophical audience interested in the study of cognition might well encounter UexkŸll for the Þrst time in the works of Daniel Dennett. Dennett describes Umwelt like this: 
ÒEvery organism, whether a bacterium or a member of Homo sapiens, has a set of things in the world that matter to it and which it (therefore) needs to discriminate and anticipate as best it can. Call this the ontology of the organism, or the organismÕs ÔUmweltÕ (von UexkŸll 1957 [2010]). This does not yet have anything to do with consciousness but is rather an ÔengineeringÕ concept, like the ontology of a bank of elevators in a skyscraper: all the kinds of things and situations the elevators need to distinguish and deal with. An animalÕs ÔUmweltÕ consists in the Þrst place of a.ordances (Gibson 1979), things to eat or mate with, openings to walk through or look out of, holes to hide in, things to stand on, and so forth. We may suppose that the ÔUmweltÕ of a starÞsh or worm or daisy is more like the ontology of the elevator than like our manifest image. WhatÕs the di.erence?Ó (Dennett 2015: 11-12) 
There are at least two di.erences. The Þrst di.erence is that organisms are living subjects and machines are not. The elevator does not ÒneedÓ anything in the same sense that an animal Òneeds to discriminate and anticipate as best it canÓ (Dennett 2015: 11-12). The organism acts in the pursuit of its own goals, including its survival. In contrast, an elevator has no goals of its own, and therefore cannot be said to ÒactÓ in the same sense. The elevator moves if the goals and actions of its human designers, builders, and riders felicitously align. Because elevators are designed to serve human needs, it may sometimes be useful to talk about them in the Ôintentional stanceÕ as Dennett does, but we need to remember that this is very di.erent from talking about organisms who have needs of their own. Di Paolo makes this argument in direct connection to the concept of Umwelt: 
ÒThe ongoing individuation, the Ôconstitutive unÞnishednessÕ of the living condition is what makes an Umwelt meaningful for organisms in ways that a network of relations is not meaningful ÔforÕ nonliving objects whose ongoing existence is not at stake. Lacks and surpluses make relational processes meaningful, but for needs and excesses to exist objectively, it is necessary for material self-individuation to be in place and for vital norms to emerge in processes of organic life, sensorimotor agency, interpersonal relations, and collective historyÓ (Di Paolo 2019: 254-255). 
These are principled reasons for rejecting the suggestion that the Umwelt of an animal or plant could be more similar to the Òontology of the elevatorÓ than to a human Umwelt (see also Thompson 
2007). For Dennett, there seems to be no fundamental di.erence between living organisms and machines which would guarantee that the Umwelten of two organisms are more similar than an Umwelt and the relationship a machine has with its surrounding. In contrast, the di.erence between animals and machines is crucial for UexkŸll, and the whole project of developing a philosophically grounded concept of Umwelt is launched as a direct attack on the Òmachine theory of living beingsÓ (von UexkŸll 2010: 41). 
The second di.erence is that we have reasons for thinking that organisms have subjective experience which do not apply to machines. Like UexkŸll, enactivists think that the experience of organisms arises from and depends on their purposeful activities of self-maintenance, growth, reproduction, and so on. An elevator does none of these things, so an argument in support of the belief that the elevator has subjective experience would have to look very di.erent. In the same text, Dennett rehearses his position that there is Òno double transduction in the brainÓ that would transduce the neuronal spike trains into Òqualia, conceived of as states ofÓ Òthe medium of consciousnessÓ (Dennett 2015: 11). Dennett uses the absence of a second transduction to conclude that there are no qualia and no medium of consciousness. We can understand UexkŸllÕs account of the construction of Umwelt as following the same path in reverse: We know that we have subjective experience, and assuming that the brain must be involved in creating it (a plausible assumption that is tacitly shared by UexkŸll and Dennett), he concludes that the activity of the brain must synthesize nervous activity into subjective experience. UexkŸllÕs account of the origin of p-Umwelt, the process whereby Òthe stimuli coming from the outside reality are translated into signs by the nervous systemÓ which Òare transposed outwards and [É] experienced as objective qualities of the worldÓ can be understood as the construction of just this medium of consciousness that Dennett denies (Brentari 2013: 17). DennettÕs account of Umwelt is opposed to UexkŸllÕs in (at least) two crucial respects: the relationship between experience and the brain, and the relationship between animals and machines. The point of this comparison is not to suggest that Dennett has no good reasons for his views, nor primarily to try to convince anyone that Dennett is wrong and UexkŸll is right. What is important for the reception of UexkŸllÕs concept of Umwelt is to point out that some of the most famous philosophers of cognitive science have cited UexkŸll while using his concept of Umwelt in a way diametrically opposed to UexkŸllÕs own views and his use of Umwelt. DennettÕs book From Bacteria to Bach and Back (2017) contains the same account of Umwelt as the passage cited above, potentially introducing a large audience to the concept of Umwelt in a way that could spreads misconceptions about UexkŸllÕs thought. Beyond the general importance of not misrepresenting the views of authors cited, texts in the philosophy of cognitive science on Umwelt continue being cited both within the Þeld and in adjacent disciplines, so avoiding or clarifying misconceptions about the term can help both ongoing and future debates (see e.g. Crippen 2020, Fingerhut 2021, Safron 2020, Schiller et al. 2023, Stapleton 2022). 

5.3 Umwelt as a bridge between ecological psychology and enactivism 
Ed Baggs and Anthony Chemero (2018) argue that the concept of Umwelt can bridge the gap between the realism of ecological psychology and the subjectivism or constructivism of enactivism, where the latter is characterized explicitly in terms of subjective experience. I will argue that this move only takes us part of the way because Baggs and ChemeroÕs account deals only with e-Umwelt, while the kind of perspective taken by enactive accounts crucially involves p-Umwelt. Making this point will involve: 
1.
 showing that the goal they pursue requires addressing p-Umwelt and not just e-Umwelt, and 

2. 
showing that their arguments only apply to e-Umwelt, but not to p-Umwelt. 


The key move of Baggs and ChemeroÕs paper is to divide James GibsonÕs concept of the environment into a habitat, which contains the environmental Òresources for a typical, or ideal, member of a speciesÓ, and an Umwelt, Òas the meaningful, lived surroundings of a given individualÓ (Baggs and Chemero 2018: 2180). They show how this distinction between the species level and the individual organism helps resolve two debates within ecological psychology: First, a.ordances can be understood as dispositional properties of a habitat and relational properties of the Umwelt of any individual animal inhabiting this habitat (ibid. 2183). Second, a habitat contains Òinformation-about the presence of ßowersÓ while the Òinformation-forÓ a given bee looking for pollen Òshould be conceived as a property of the umweltÓ (ibid. 2184). Baggs and Chemero then turn to the di.erences between ecological psychology and enactivism. Since this is arguably the most ambitious and far-reaching application of Umwelt within embodied cognition, I will outline the philosophical context before discussing the details of the argument. 
The ultimate goal of the paper is to harmonize the conceptual foundations of ecological psychology with those of enactivism. If successful, this would serve to unite a sizable portion of 4E cognition under a common framework. The term 4E cognition stands for embedded, embodied, extended, and enactive cognition, sometimes with an added A for a.ective. Though contested, the label has emerged as a useful shorthand for talking about a variety of approaches to the study of cognition which are bound together primarily by their opposition to the computationalist, representationalist paradigm of classical cognitive science. To various degrees and in di.erent combinations, proponents of these 4E approaches argue that we should conceive of mind not as a rule-based manipulation of symbols, as abstract information-processing, or as an algorithmic mode of problem solving physically instantiated in the brain, but instead start from a conception of the mental as consisting of integrated processes of action and perception in a dynamical system made up of the entire organism and its environment. These interventions in the meta-theoretical foundations of cognitive science have proven fruitful in the production of novel avenues of research and theory while simultaneously being contentious, both in their engagement with the orthodox approaches they oppose and in their critical disagreements amongst each other. 
The opposition addressed by Baggs and Chemero is one which exists between Gibsonian ecological psychology and enactivism, two prominent approaches within 4E cognition. While ecological psychology seeks to explain the externally observable behavior of subjects purely in terms of how this behavior is determined or guided by the structure of the subjectsÕ environment, explicitly rejecting any appeal to factors internal to the subject, it is precisely this subjective interiority around which the enactivist reconception of cognitive science is constructed (Chemero 2009; KŠufer & Chemero 2015; Thompson 2007). Enactivism was originally conceived by Francisco Varela, Evan Thompson, and Eleanor Rosch in The Embodied Mind (1993[1991]), and subsequently reÞned by Thompson in Mind in Life (2007), amongst others. This approach awards central import to the subjectÕs own experience, and mobilizes di.erent techniques from phenomenology and Buddhist meditative practices for the systematic investigation of experience (Varela, Thompson & Rosch 1993; Thompson 2007). According to Thompson, this explicit emphasis on subjective experience brings out something that is already implicitly a fundamental aspect of all scientiÞc psychology, since Òscientists rely substantially not only on subjectsÕ introspective reports, but also on their own Þrst-person experienceÓ, without which they would Òbe unable to make sense of what subjects are sayingÓ (2007: 311). 
Not all existing varieties of enactivism share this focus on experience (Ward, Silverman, & Villalobos 2017). However, Baggs and Chemero explicitly deal with this classical conception which Òis uniÞed by an emphasis on the actorÕs phenomenology and agencyÓ (2177). Furthermore, there is disagreement on whether contemporary approaches which omit these key experiential aspects of the original Òenactive approachÓ should really be labeled as ÔenactiveÕ (Baggs & Chemero 2018: 2177; Hutto & Myin 2017; Thompson 2018). Tracing back the negative views that each side holds of the other to di.erences in their graduate educations, Baggs and Chemero report that ecological psychologists often think that Òenactivists are idealists who neglect the worldÓ while enactivists hold that Òecological psychologists are realists that neglect experienceÓ (2176). From these references to subjective experience, it is clear that the contrast between ecological psychology and enactivism does not only concern the di.erence between an ÒontologicalÓ and an Òepistemic strategyÓ, but that the issue of subjective experience plays a crucial role for the enactivist view (ibid. 2175). With its focus on the phenomenology of the subject, an enactive account of the Umwelt needs to include not just the e-Umwelt, but the p-Umwelt of the subject. Otherwise, the enactivists would be neglecting experience in just the way they charge ecological psychologists with. In the following, I will summarize Baggs and ChemeroÕs strategy for introducing Umwelt into this debate and show that their arguments only take us from the physical environment to the e-Umwelt of a subject, but not to its p-Umwelt. 
ChemeroÕs approach to what he calls ÒRadical Embodied Cognitive ScienceÓ is grounded in James GibsonÕs foundational work in ecological psychology and upholds its basic commitments (Chemero 2009; KŠufer & Chemero 2015). As a behaviorist, Gibson sought to explain the behavior of animals in such a way Òthat the control of action was not the result of a centralized executive making plans based on representations of the environment,Ó but rather the result of objective stimuli present in the environment (Chemero 2009: 101). In his view, Òinformation in the surrounding environment was su.icient to control behavior (without, that is, mentally added information, computation, or inference, and without a mentally represented plan)Ó (Chemero 2009: 101). GibsonÕs research builds on the assumption that Òbehavior is regular without being regulatedÓ and developed his account of the environment in order to explain how this could be possible (Gibson 1979; cited in Chemero 2009: 103). 
Central to GibsonÕs notion of environment is that, unlike the physical world, it is made up not of intrinsically meaningless objects and processes, but of a.ordances, objects we directly perceive as meaningfulÑwithout having to interpret them Þrst or process any informationÑand which a.ord us certain actions. GibsonÕs conception of a.ordances as Òopportunities for actionÓ was inspired by the notion of valence from Gestalt psychology (KŠufer & Chemero 2015: 156). Kurt Ko.ka and Kurt Lewin had used the term valence to describe a property of an object which makes it attractive or repellant, and thus elicits certain forms of behavior rather than others. While they argued that the valence of an object is directly given in perception, Gibson went further in claiming that valences and a.ordances are Òcomponents of the objective worldÓ (KŠufer & Chemero 2015: 149-150). In contrast to the Gestalt psychologists, who di.erentiated between a phenomenal object and its physical equivalent, Gibson insisted that there was only one object, and that a.ordances thus had to exist independently of the subjects to whom they a.ord actions (Baggs & Chemero 2018: 2177, 2182-3). He was convinced that meaning must be an objective feature of the world and not something created by the mind of a subject, not only because of his behaviorism, but also because he thought that Òany morally acceptable psychology must be grounded in a realist understanding of the worldÓ (Baggs & Chemero 2018: 2182). The central challenge for ecological psychology, then, is to provide an account of meaning that is both naturalistÑin that the Òphysical world is made of whatever invisible particles physicists talk aboutÓ and Òinherently meaninglessÓÑand behavioristÑin that meaning is not added by the subject but present in the environment as an objective stimulus (Baggs & Chemero 2018: 2178). If it is neither purely physical, nor subjective, what then is the environment described by ecological psychology? This is the question that the term Umwelt is meant to help answer. 
UexkŸllÕs concept of Umwelt does double duty in BaggsÕ and ChemeroÕs move towards unifying the philosophical foundations of radical 4E cognition. Primarily, the term Umwelt is introduced to amend the distinction between physical space and the environment of Gibsonian ecological psychology. By further di.erentiating between the lineage-speciÞc habitat of a species and the Umwelt of an individual organism, the terminology becomes more Þne-grained, enabling the authors to settle long-standing disputes within ecological psychology about the nature of GibsonÕs a.ordances and the status of information. In addition, the term Umwelt also serves as a bridge concept between the objectivist, realist perspective of ecological psychology and the subjectivist, constructivist perspective of enactivism, by providing ecological psychology with a coherent account of how the physical world and the world of phenomenal, meaningful experience are related. 
Baggs and Chemero trace the source of much disagreement within ecological psychology back to the initial distinction Gibson draws between the physical world and the environment in which animals live. Their solution is to subdivide the environment into the habitat of a species and the Umwelt of an individual animal. The introduction of this sub-distinction allows Baggs and Chemero to resolve debates within ecological psychology about the central concepts of a.ordance and information. The habitat-Umwelt distinction, according to Baggs and Chemero, allows us to view these competing positions as complementary descriptions of the same phenomena at di.erent levels, rather than mutually exclusive options between which we must choose. Are a.ordances dispositional properties of objects, or are they relational properties that hold between objects and organisms? Baggs and Chemero suggest that they are both: a.ordances may be considered dispositional properties when seen at the level of a species and its habitat, and relational properties when considered as parts of a single organismÕs Umwelt. Does information about the structure of an environment exist independently of any actual organism, or is information a part of the sensorimotor activity an organism engages in when exploring its surroundings? Again, the two are portrayed as complementary rather than competing: the habitat contains information about its structure, while an animal seeks out information for its meaningful engagement with its Umwelt. This distinction between habitat and Umwelt is also a solution to an issue we encountered in chapter 3, the question of whether Umwelt pertains to a species or to an individual: Both options can be useful, but we need to distinguish between them, which Baggs and Chemero achieve by reserving the term Umwelt for the latter. 
Beyond solving these internal debates, the introduction of Umwelt into the conceptual repertoire of ecological psychology is meant to strengthen its rapport with enactivism. This is the main goal of Baggs and ChemeroÕs paper: to forge a path towards a synthesis of the ecological and enactive approaches by showing that, despite their apparent disagreements, they turn out to be merely two complementary perspectives on the same set of phenomena. In order to demonstrate this, Baggs and Chemero pursue two main lines of argument. The Þrst focuses on the environment and describes a single world which is continuous across the di.erent scales of physical universe, species habitat, and individual Umwelt. The second focuses on the individual organism and explains how di.erent physiological abilities as well as learned skills and acquired knowledge determine which a.ordances present in a given habitat become part of an individualÕs Umwelt. I argue that neither strategy takes us from a conception of a meaningless physical world to the p-Umwelt that enactivists place central importance on. Instead, the Þrst move gets us from the physical world to the e-Umwelt of an individual organism, while the second move shows that the e-Umwelt of an individual organism is open, in the sense that its behavioral repertoire can grow over time. I will address each in turn. 
The Òkey to GibsonÕs theory of a.ordancesÓ is his distinction between physical space and the environment of animals (ibid. 2178). A central part of this concerns scale: Òphysical world exists at all spatial and temporal scales, from nanoseconds and nanometers to millennia and galaxiesÓ (ibid. 2178). In contrast, the environment of animals occupies the Òmiddle scale,Ó and for humans the Òspatial scale of the environment is from millimeters to kilometers; the temporal scale is from hundreds of milliseconds to decadesÓ (ibid. 2178). This distinction gives us the impression of zooming in on the Umwelt, from the complete picture of the universe to just the tiny section of it that is relevant for a species, and even further to just the Umwelt of a given individual organism. This visualization is in concord with the attempt to describe one single continuous world, and matches the description of Umwelt as a Òsubset of the physical worldÓ (ibid. 2179). The problem is that this move is set up in such a way that it is impossible to arrive at the p-Umwelt of an individual animal from the very beginning. The subjective experience of an animal is not visible from an outside perspective, no matter how far we zoom in. Another way to frame this problem is by focusing on the notion of a ÒsubsetÓ. If we start from the fact that the Òphysical world is made of whatever invisible particles physicists talk aboutÓ, no subset of what this world contains will consist of subjective experience (ibid. 2178). This is why moving from the Òmeaningless physical worldÓ to the habitat as Òa subset of the physical worldÓ and Þnally to the Umwelt of an individual as Òa subset of the species-general habitatÓ cannot take us to the p-Umwelt of this animal (ibid. 2179, 2184). Taking the subset of a subset is a process of sequential selection, mirroring one of the positions in the disagreement about whether UexkŸllÕs account of Umwelt revolves around selection or construction. As we saw in chapter 3, a process of selection can pick out those features of the physical environment which make up an animalÕs e-Umwelt, but since its subjective phenomenal experience is not contained in the perspective of an external observer, selection cannot account for p-Umwelten. This is why the deÞnition of physical world, habitat, and Umwelt as a sequence of nested subsets succeeds at resolving disagreements between di.erent positions within ecological psychology, all of which describe a living subject from an external perspective, but cannot bridge the gap between this external perspective and the subjectÕs own p-Umwelt. 
The di.iculty in connecting an account of the physical world to the subjective experience of an individual animal arises because the authors uphold a steadfast commitment to GibsonÕs conviction that there is no Òdistinction between the world we experience and the world-in-itselfÓ (Chemero & KŠufer 2015: 151), a form of realism inspired by William JamesÕ view that Òthere is only one worldÓ (ibid. 148). This view seems pleasantly parsimonious when talking about objects, e.g. when Gibson rejects the Gestaltist distinction between a phenomenal postbox and a physical postbox, preferring to talk only of Òthe real postbox (the only one) [which] a.ords letter-mailing to a letter-writing human in a community with a postal systemÓ (Gibson 1979: 139, quoted in Baggs & Chemero 2018: 9). It gets much more complicated when we look at subjects instead of objects. In the case of the postbox, ÒexperienceÓ clearly refers to the experience of a third person observer, because the postbox (presumably) does not experience anything. When we consider the perspective of a scientiÞc observer on a world populated by living subjects, however, there is a crucial di.erence: the experience of each living subject is not observable from the outside by a third party. In the same vein, Baggs and ChemeroÕs claim that we Òperceive the umwelt of other humansÓ is immediately plausible only for e.Umwelt (2187). Their example that I can Òperceive that the Japanese newspaper a.ords reading for SatoshiÓ does not mean that I have access to SatoshiÕs phenomenal experience, in the same way that I can see a dog or cat perk up when they hear a sound that is outside my auditory range without thereby in any way gaining auditory access to their phenomenal experience. I can pick up information about the e-Umwelten of other subjects based on behavioral cues that are observable from the outside and available to my sensory apparatus, but I cannot thereby access their subjective experience, their p-Umwelten. In contrast, the claim that we perceive the p-Umwelten of other humans is much stronger and would require dedicated arguments about the structure of subjective experience. One view that seems to endorse this claim will be discussed in the next chapter. 
The second main line of Baggs and ChemeroÕs argument concerns how the makeup of an individual organism a.ects which a.ordances are contained within its Umwelt. Whereas the habitat of a species only narrows down the physical universe to those scales and aspects which are in principle accessible and relevant to the perceptions and actions of a given animal species, the Umwelt of an individual organism is more speciÞc: idiosyncrasies in the physiology and psychology of any given organism caused by its unique ontogenetic history constitute a further Þlter on which a.ordances are actualized in its Umwelt. Thus, a human being who has Òlearned to read Japanese kanji, to play bass, to do tricks on a skateboardÓ encounters a whole set of a.ordances in the exploration of their Umwelt that is not available to another human being navigating the same physical environment without possession of any of these skills (ibid. 2186). Baggs and Chemero leverage this account in order to address a central concern: Òhow do we incorporate Þrst-person experience into cognitive science without sliding into a solipsistic view of the mind? The concern is that we are each trapped inside our own umweltÓ (2187). This worry follows their account of how enactivists think about Umwelt and subjective experience, and about the points on which the authors agree with the enactivists. The enactivists, Òinspired largely by phenomenology,Ó start with the Umwelt which is Ògiven in experienceÓ to an individual (2186). A Husserlian phenomenologist Òhas to bracket questions about the world beyond the experiences [, but the] umwelt, of course, cannot be bracketedÓ (2186). Comparing their own position to that of the enactivists, they state that: 
Òwe agree that the umwelt is privileged in some sense: the umwelt has a Þrst-person perspective; the umwelt is the set of a.ordances that are available to an individual animal, given the animalÕs biological make up, its development, its history of learning. Phenomenologists (and enactivists) describe this privilege by saying that the umwelt is given in experience; ecological psychologists (and enactivists) describe this privilege by 
saying that the umwelt is perceived directlyÓ (2186-7). 
It is important to note here that it is not clear that both sides are indeed talking about the same privilege. The phenomenological method of investigating experience starts by investigating oneÕs own experience, because that is what one has immediate access to. The sense in which the p-Umwelt is privileged for a given subject is that anything that is given in experience to this subject is part of its p-Umwelt, and only its p-Umwelt is given to it in experience. In contrast, the description given by ecological psychology does not need to involve subjective experience at all: a set of a.ordances and the history that made it possible can be described by an external observer, and the ÒÞrst-person perspectiveÓ might refer not to phenomenal experience as such, but to the fact that an animalÕs sensory organs can occupy di.erent points in space and face in di.erent directions depending on the animalÕs own movements, similar to how the viewpoints of di.erent individuals are discussed by James Gibson (see Baggs and Chemero: 2180). In this case, the discussion would not concern p-Umwelt itself and the privilege in question would not be about phenomenal subjective experience, but only about which subset of features from the environment is available to an agent. 
It is against this backdrop that we must consider Baggs and ChemeroÕs characterization of what this second line of argument achieves: ÒThe way to avoid solipsism, for radical embodied cognitive scientists, is to adopt a historicalÐdevelopmental perspectiveÓ (2187). In this context, the reference to solipsism seems to suggest that the concern about being Òtrapped inside the umweltÓ concerns p-Umwelt. The view that a subject only ever has access to their own experience, i.e. that their p-Umwelt is closed, would here be described as a form of solipsism that should be avoided. But what does the appeal to development show? Baggs and Chemero reference VygotskyÕs account of child development to argue to show how a toddlerÕs Òumwelt is expandedÓ through learning and conclude that Ò[t]o the extent that we are able to learn throughout our life, the umwelt never constitutes a limit on our experienceÓ (2187). The childÕs acquisition of a new skill, such as pointing, might be compared to the addition of a new functional cycle in UexkŸllÕs perspective. The ball in the corner now takes on the a.ordance of being point-at-able in addition to its previous a.ordance of being pick-up-able. Importantly, this whole description can be given without reference to subjective experience, and it only constitutes a demonstration of openness for e-Umwelt. As discussed in chapter 4, to show that e-Umwelt is open rather than closed, exactly this kind of demonstration is necessary and su.icient. But to show that p-Umwelt is open involves something very di.erent: the demonstration that subjective experience is not private in the sense of not being directly accessible to an external observer. The distinction between e-Umwelt and p-Umwelt also helps assess Baggs and ChemeroÕs assertion that Ò[i]f we were trapped inside the umwelt, then learning would be impossibleÓ (2187). Based on the discussion in chapter 4 of what it means for e-Umwelten to be open or closed, this claim holds for e-Umwelten. But it does not apply to p-Umwelten: The fact that I learn things does not render my phenomenal experience accessible to others (or vice versa), nor does it follow from the claim that my experience is private that I cannot learn anything. Consider the case of learning to read Ancient Greek. Before I learn which letters individual words are composed of, I have to learn to identify the shapes of the di.erent letters. But in order to learn to identify the letters, I have to already be able to see them. Only because the letters already a.ord seeing to me can I learn to identify them. Learning to read Ancient Greek thus increases the number of a.ordances in my p-Umwelt, but always progresses from something that is already given in my experience. Similarly, learning some piece of information not from experience but from others also does not transcend my p-Umwelt in this important sense: Once I learn that Paris is the capital of France, I am able to imagine Paris and think about it in new ways, but whether I learned it from a book or from conversation, the way in which I learn it depends on something that happens in my experience. Baggs and ChemeroÕs account of how the Umwelt of a learner expands throughout development shows that e-Umwelten are open, but does not show us whether p-Umwelten are open or closed. 
As we have seen, starting with the external perspective of ecological psychology and introducing Umwelt to create a more Þne-grained distinction between di.erent kinds of environment can help pick out the e-Umwelt of an individual, but it does not bridge the gap between an external perspective on an organism and the subjective experience of the organism itself. Likewise, appealing to learning and development shows that the e-Umwelt of an agent can expand, but it does not render the p-Umwelt of that agent accessible from an external perspective. Because of this, those aspects of enactivism which are concerned with the subjective experience of an organism are still outside of the scope of this Umwelt-enriched account of ecological psychology. A helpful contrast exists between Baggs and ChemeroÕs account and another view developed by the ecological psychologists Martin Fultot and Michael Turvey (2019), who adopt UexkŸllÕs musical metaphors but reject the concept of Umwelt. 

5.4 Ecological psychology with UexkŸll but against Umwelt 
Martin Fultot and Michael Turvey (2019) also adopt UexkŸllÕs thought for ecological psychology, but in a way that is diametrically opposed to Baggs and ChemeroÕs account. Instead of introducing the term Umwelt into ecological psychology, Fultot and Turvey argue that Umwelt is fundamentally at odds with basic tenets of ecological psychology and instead use UexkŸllÕs musical metaphors about harmony in the natural world as an ÒantidoteÓ to his Kantian constructivist view of subjects and their worlds. In this section, I will use the distinction between e-Umwelt and p-Umwelt to show that the argument they adopt from Gibson as a reason to reject Umwelt misses the mark. I will also show how the musical metaphors which they adopt from UexkŸllÕs A Theory of Meaning are rooted in a romanticist and holist philosophy of nature and draw into question their beneÞt for the philosophy of cognitive science. Additionally, it is useful to discuss Fultot and TurveyÕs view because it a.irms that di.erent parts of UexkŸllÕs thought can be separated from each other and adopted or discarded selectively. The very possibility of doing this has been denied by Sprenger and Schnšdl, as discussed in chapter 2. So far, we have seen several examples of using Umwelt without adopting any organicism or holism about the totality of nature, and Fultot and Turvey provide us with an example of the reverse choice: adopting the musical metaphor of nature as a grand symphony while rejecting the concept of Umwelt. 
Fultot and Turvey reject UexkŸllÕs claim that each organism constructs its own world as representationalist. They highlight how the construction of Umwelt as modeledÑin an idiosyncratic wayÑon Kantian epistemology parallels key aspects of cognitivism that ecological psychology rejects. Instead of the concept of Umwelt, which entails that there are Òas many worlds as there are subjects,Ó Fultot and Turvey develop an understanding of nature as a uniÞed world in which all elements are harmoniously interconnected by melodies, harmonies, and counterpoints of meaning from a reading of UexkŸllÕs A Theory of Meaning (von UexkŸll 1926: 70; von UexkŸll 2010). 
To argue against UexkŸllÕs doctrine of many worlds, Fultot and Turvey recapitulate GibsonÕs rejection of the Gestalt theoristsÕ subjectivist conception of Ò[A]u.orderungscharakterÓ, which Gibson translated as Òa.ordanceÓ (Fultot and Turvey 2019: 14). They note the links between Gestalt theory, Gibson and UexkŸll, but also emphasize the conceptual tensions between them. In his development of a.ordances as Òorganism-relative without being organism-dependent,Ó they take Gibson to be implicitly Òtargeting von UexkŸllÕs theory and theories like itÓ (ibid. 15). The argument hinges on the question of whether there is Òa unique, private access of each individual organism to its surroundings,Ó which UexkŸll endorsed and Gibson rejected (15). Fultot and Turvey follow Gibson in tracing this view back to the fact that Òno two individuals can occupy the same geographical point at the same timeÓ (15). According to Gibson, the primary reason to think that each living organism lives in its own subjective world is based in Òa narrow conception of optics and a mistaken theory of visual perceptionÓ (Gibson 1979: 38, as quoted in Fultot and Turvey 2019: 15). 
Read as a criticism of UexkŸll, this misses the mark. UexkŸll held that the Òunique, private access of each individual organism to its surroundingsÓ concerns p-Umwelt, but not e-Umwelt. The latter is part of the scientiÞc knowledge about the animal that a researcher can gain by studying it as an external observer. In contrast, UexkŸll holds p-Umwelt to be private in exactly this sense, since only the animal itself has its own experience, and the scientiÞc observer in turn only has their own experience. But the reason for this is not that two subjects cannot occupy the same point at the same time. This line of thinking treats the ÔÞrst-person perspectiveÕ like a mere combination of location and direction in physical space. The sense in which p-Umwelt involves a Þrst-person perspective is that the world as I experience it is given to me as seen through my eyes, in the form of phenomenal experience. My access to my p-Umwelt is not unique because the contents of my experience are qualitatively di.erent from everyone elseÕs at any given time, but because I am the only one having this experience, 
i.e. my p-Umwelt is numerically distinct from other p-Umwelten. 
The problem that UexkŸllÕs constructivist account of the construction of p-Umwelt seeks to solve is posed in terms opposed to those of GibsonÕs ecological approach. Where Gibson considers a single environment containing meaningful a.ordances and which Òall inhabitants have an equal opportunity to explore,Ó for UexkŸll the main explanatory work has to start earlier (Gibson 1979: 38, quoted in Fultot and Turvey 2019: 15). The problem is not that di.erent organisms cannot occupy the same point in an environment at once, it is that they each have to construct their environments as given in subjective experience on the basis of physical stimulations which by themselves involve no experience. Once an organism perceives meaningful a.ordances, indeed as soon as it experiences any environment at all, we are already in medias res, and much of what UexkŸll describes has to have taken place already as the condition of the possibility of this experience. The Umwelt of an animal has to be accounted for because the colors that a bee sees are neither part of the objective material world described by the physicists, for whom there are Òonly waves, after all, and nothing more,Ó nor do they coincide with the colors that humans see (von UexkŸll 2010: 134). More than that, each bee has to generate their own experience as an organismic activity in contact with its physical surroundings (see also chapters 2 and 3). The dynamical relationship of the organism to its physical surroundings gives rise to its subjective experience of its p-Umwelt. 
Fultot and Turvey point out the sharp contrast between UexkŸllÕs Kantian constructivism and the conceptual underpinnings of GibsonÕs direct realism. As an alternative to the notion of Umwelt, they introduce a second theory of meaning in nature found in UexkŸllÕs Bedeutungslehre (Þrst published in 1940). This later text, which was published in English translation as A Theory of Meaning together with the slightly earlier Foray, develops an account of why the structures of living organisms Þt so perfectly into their environment of other organisms and the inorganic world. As a staunch critic of Darwinism, UexkŸll sees the harmonious composition of the natural world as evidence of a greater plan that orders the realm of the living into one overarching symphony of meaning, composed of countless melodies, harmonies, and counterpoints. 
Fultot and Turvey highlight a series of parallels between UexkŸllÕs musical theory of meaning and GibsonÕs emphasis on a Òcomplementarity between organism and environmentÓ that enables the former to directly pick up on a.ordances speciÞed by information available in the latter (18). They outline two ways of conceiving the organism/environment relationship, as the familiar representationalist dualism that they argue should be rejected, or as a duality, which involves a di.erent kind of symmetry between organism and environment. Where a representational symmetry involves Òthe preservation of all the relations and their order,Ó duality preserves Òthe number of relations but can transform their quality and revert their orderÓ (19). Representation entails the creation of duplicates or copies, while duality works on the basis of correspondences, such as the peg of a cogwheel Þtting into the socket of another. 
Two problems with this evaluation of UexkŸllÕs musical theory of meaning arise: First, the account of meaning in nature as one great holistic symphony does not replace the constructivism of Umwelt, it complements it. Second, the arguments that UexkŸll provides in support of this musical theory of meaning are quite di.erent from the Kantian constructivism of Umwelt, but they are not free from conceptual baggage. On the contrary, they are drawn in part from Hans DrieschÕs neovitalism and GoetheÕs romantic holism. These views depart so radically from generally accepted philosophical assumptions in contemporary philosophy of the natural sciences that they require substantial amounts of conceptual work before they can be integrated into existing accounts of embodied cognition. 
In their careful reading of A Theory of Meaning, Fultot and Turvey identify an Òimplied realism about the properties of the environmentÓ (20). They cite UexkŸllÕs description of an octopus, where he states that the Òincompressibility of the water is the precondition for the construction of a muscular swimming sacÓ (von UexkŸll 2010: 173). The incompressibility of the water does not depend on the existence of the octopus as subject, illustrating the point that the role played by seawater in the meaningful activity of swimming is Òorganism-independent yet organism-relativeÓ (Fultot and Turvey: 20). ÒMeaning is already there, so to speakÓ (ibid. 20). Two points relativize this realism. Even though we are taking an external perspective on the octopus that allows us to understand its place in a system of meaning by reference to a larger harmonious whole rather than purely as constructed by the octopus itself, A Theory of Meaning does not constitute a departure from UexkŸllÕs Umwelt theory. Besides the musical theory of meaning, the text still contains the same constructivist view of how a subject creates its Umwelt: ÒThe sun is a light in the sky. The sky is, however, a product of the eye, which constructs here its farthest plane, which includes all of environmental spaceÓ (von UexkŸll 2010: 190). According to UexkŸll, this principle of how a subject constructs its p-Umwelt is valid for octopi just as it holds for humans, and scientists too can only ever investigate their own Umwelten (von UexkŸll 2010: 207). The incompressibility of the water has octopus-independent reality, but always within the Umwelt of a subject. In this case, the subject is a musical ecologist analyzing Òthe octopus as subject in relation to the seawater as carrier of meaningÓ (von UexkŸll 2010: 173). UexkŸll ends both A Theory of Meaning and the Foray with the reminder that the limitations of Umwelt also apply to our scientiÞc endeavors. Fultot and Turvey are exaggerating when they claim that Òhis Kantian views having been abandonedÓ in the musical theory of meaning (24). 
As Umwelt grows out of UexkŸllÕs reading of Kant, so his musical theory of meaning grows out of romanticist holism and the neovitalism of Hans Driesch. UexkŸll and Driesch had met in Naples in the 1890s, where UexkŸll was researching the physiology of Eledone moschata while Driesch studied the development of sea urchins (Mildenberger and Herrmann 2014a: 5, 2014b: 274-276). Driesch demonstrated that Òa sea urchin germ cell cut in half became not two half, but two whole sea urchins of half the size,Ó which to UexkŸll demonstrated that nature is not exhausted by mechanical explanation and warranted far-reaching conclusions: ÒEverything physical can be cut with a knifeÑ but not a melodyÓ (von UexkŸll 2010: 194). UexkŸll agrees with Karl von Baer that there is a Ògoal.pursuing quality in the emergence of living beingsÓ and identiÞes musical harmony as the driving force of this teleological embryogenesis: 
Òplanned embryonic development [É] beings with the three beats of a simple melody: morula, blastula, and gastrula. Then, as we know, the development of the buds of the organs begins, which is Þxed in advance for every animal species. This proves to us that the sequence of formal development has a musical score which, if not sensorily recognizable, still determines the world of the senses. This score also controls the 
spatial and temporal extension of its cell material, just as it controls its propertiesÓ (von 
UexkŸll 2010: 159, 160). 
To todayÕs reader, the role of the melody in this account of embryogenesis is at best a poetic placeholder that has to be replaced by scientiÞc explanations and at worst a kind of vital life force. The latter option is unfortunately very plausible, as Driesch was a leading proponent of neovitalism (Mildenberger and Herrmann 2014a: 5, 6). While Fultot and Turvey choose to ignore UexkŸllÕs appeals to an overarching plan in nature as Òcreationist-sounding,Ó it seems that his vitalistic tendencies are tightly linked to the musical account of biological form and cannot so easily be separated from it (Fultot and Turvey 2019: 18). 
The second philosophical source from which UexkŸllÕs musical theory of meaning draws its strength is a romanticist holism. The melodies, harmonies, and counterpoints are an explanation rather than a description of the organization of the biological realm only if we accept a holistic worldview in which wholes determine their parts in accordance to an overarching and preexisting schema, rule, or Òprimal image [Urbild]Ó (von UexkŸll 2010: 159). This principle, which we saw in action in the embryogenic formation of a sea urchin in accordance to its Òprimal score,Ó goes back to GoetheÕs famous Urpßanze (160). Frederick Amrine has outlined UexkŸllÕs deep debt to Goethe, with whom he sides against Newton in the question of color perception (Amrine 2015: 50). Amrine explains UexkŸllÕs musical theory of meaning as an instance of Goethean ecology, and his arguments are convincing: A central refrain in A Theory of Meaning is developed from Goethe (who in turn is alluding to PlatoÕs Republic): 
ÒIf the ßower were not bee-like, If the bee were not ßower-like, The harmony would never succeed.Ó (von UexkŸll 2010: 198) 
This is based in GoetheÕs claim that: 
ÒWere the eye not sunlike 
It could never gaze upon the sun.Ó (von UexkŸll 2010: 190). 
The vision of nature that UexkŸll expresses in musical terms is deeply grounded in romanticist holism, and the Òmeaning planÓ which guarantees that its parts, developing in accordance with their 
Òprimal imagesÓ and Òprimal melodies,Ó Þt into the overarching harmony is guaranteed by GoetheÕs Spinozist ÒGod-NatureÓ (von UexkŸll 2010: 192). The problem for us today is that UexkŸll is tapping into an entirely di.erent conception of science than the one that has dominated the last centuries and that is accepted today. For UexkŸll, Ò[m]eaning is the pole star by which biology must orient itself, not the impoverished rules of causalityÓ (von UexkŸll 2010: 160). Besides its roots in romanticism, Di Paolo provides another good reason for caution about holistic harmony: 
Òwhile we must avoid the ßattening out of the biological and psychological worlds into a series of mechanisms, we must also be cautious with the theme of the harmony of the world [É] if we understand harmony as a primordial state of mutually counterpunctual relations of meaning (Òthe spider is ßy-likeÓ). Here, what is excluded, to repeat, are the precarious conditions and the ongoing, e.ortful processes by which meaning is achieved whatever the timescale, whether evolutionary, developmental, or behavioralÓ (Di Paolo 2019: 254). 
In the context of UexkŸllÕs holism, it is worth mentioning that his belief in a great whole that uniÞes individual organisms under one rule of meaning found a deeply disturbing expression in his Staatsbiologie. In 1920, UexkŸll Þrst published this interpretation of the state as a biological organism. After GermanyÕs defeat in the First World War, UexkŸll had become increasingly antisemitic and began channeling this conviction in his academic writing ((Mildenberger and Herrmann 2014b: 294, 295). A second edition of the book published in 1933 included a partially rewritten section on Òthe diseases of the state [Die Krankheiten des Staates],Ó which identiÞes members of foreign races who are detrimental to the state as ÒparasitesÓ (von UexkŸll 1933: 59, 72). UexkŸll concludes the book by praising the Òingenious doctorÓ into whose care Germany has delivered itself as a Òdeeply sick patientÓÑa reference to Adolf Hitler (von UexkŸll 1933: 79; Winthrop-Young 2010: 226, 227). These connections between romanticist holism and fascism in UexkŸllÕs work are deeply disconcerting (see Harrington 1996). To be clear, the musical holism of A Theory of Meaning itself contains none of these vile totalitarian biologisms, and using its concepts in ecological psychology would not thereby import anything objectionable. However, it still seems important to mention this aspect of UexkŸllÕs work in any discussion of his holism. 
One problem with using A Theory of Meaning to bolster an account of the organism/environment relation in embodied cognition is that its main function in UexkŸllÕs work is to provide an account of the appearance of design in nature. This was a desideratum for UexkŸll because he Þrmly rejected the Darwinian account. That is not a pressing question for us today. Few people doubt that our best explanation for why the spider spins a web that corresponds so well to the structure of the ßy will invoke Darwinian evolution. The potentially useful part of A Theory of Meaning is its account of meaning understood through the musical concepts of harmony, melody, counterpoint, and so on. However, most of the arguments given in support of this musical account derive from neovitalism and Goethean ecology. Were we to remove all elements that are not immediately compatible with our contemporary understanding of natural science, A Theory of Meaning does not seem to o.er much argumentative support for an account of how organisms are attuned to their environments. There are interesting parallels to GibsonÕs ecological approach, and some of UexkŸllÕs descriptions provide vivid illustrations to the principles of ecological psychology, but it is unclear what is added to its explanatory power or conceptual clarity by bringing in UexkŸllÕs musical idiom. 
Even if we accept UexkŸllÕs musical theory of meaning and the overarching harmony guaranteed by its elusive plan, this only accounts for the appearance of design in nature, not for the experience of living subjects. What the musical holism explains is why the di.erent organisms observed in nature appear to Þt each other and their environments so perfectly. This explains why the Merkwelt and Wirkwelt of e-Umwelt Þt together in functional cycles. It does not contain an account of why the execution of functional cycles involves the subjective experience of p-Umwelt. UexkŸllÕs musical holism does not appear to o.er any help in grappling with the problem of accounting for subjective experience in a scientiÞcally grounded account of mindÑthe Òexplanatory gap between consciousness and natureÓ, so it cannot replace the account of Umwelt that Fultot and Turvey want to avoid (Thompson 2007: 10). 

5.6Conclusion 
A critical analysis of the reception of UexkŸllÕs concept of Umwelt in the philosophy of cognitive science a.irms the importance of distinguishing between e-Umwelt and p-Umwelt. Clark and Dennett cite UexkŸll and use his term Umwelt decoupled from the question of subjective experience, running the risk of creating a false impression of UexkŸllÕs thought for their readers. Distinguishing between e-Umwelt and p-Umwelt would be one way of clarifying that a speciÞc usage of the term Umwelt does not concern the subjective experience of a system under discussion, or that a system without subjective experience is discussed as having an e-Umwelt, without thereby suggesting that UexkŸllÕs conception of Umwelt is not centrally concerned with subjective experience. For Baggs and ChemeroÕs adoption of the term Umwelt, di.erentiating between e-Umwelt and p-Umwelt makes it clearer which conceptual disagreements can be resolved through the concept of Umwelt and which cannot. Crucially, the concept of Umwelt cannot bridge the gap between the perspective of an external observer and a subjectÕs own experience, since this gap persists as the di.erence between e-Umwelt and p-Umwelt. 
UexkŸllÕs own methodological strictures about the epistemic limits of external observation, which underly the distinction between e-Umwelt and p-Umwelt, are based on the view that oneÕs subjective experience is fundamentally private. The next chapter will address what it would mean to hold that subjective experience is instead shared in a strong sense, discuss one enactivist account that seems to endorse strong sharing, and evaluate the arguments given in favor of it. 
Chapter 6: Does embodied intersubjectivity show that p-Umwelten are open? 
6.1 What does it mean to share an experience? 
In chapter 3 I showed that UexkŸll uses Umwelt in two distinct senses: I call the scientific description of an organismÕs Umwelt based on what is accessible from the perspective of an external observer the e-Umwelt and the Umwelt as it is given to the organism itself in subjective experience the p-Umwelt. The distinction itself partly results from UexkŸllÕs belief that subjective (or phenomenal) experience is private. On this view, the fact that a scientist cannot access the subjective experience of a sea urchin is just one instance of the more general state of affairs that the subjective experience of each individual is private. Another way to state this view is to say that the p-Umwelten of all individuals are closed. In this chapter, I discuss the account of human intersubjectivity given by Fuchs and De Jaegher (2009) which seems to posit the occurrence of shared subjective experience to account for certain social encounters. Endorsing such a view entails that the p-Umwelten of humans are at least sometimes open rather than closed. I argue that neither the way we experience the events of our personal lives nor prominent phenomenological analyses of intersubjectivity require that we posit strong sharing. I conclude this chapter by proposing an alternative view on which the social encounters in question can be accounted for without positing strong sharing. Before discussing Fuchs and De JaegherÕs view, some comments on the topic of subjective experience are necessary. 
The way we talk about sharing mental states is fundamentally ambiguous. When we say that two people share an emotion, a belief, or an experience, we may take this to mean either that the two persons are in mental states that are qualitatively identical, or that these mental states are numerically identical. In the latter case, we are talking only about one single mental state, which is shared between the two persons in a strong sense. Put differently, we might be talking about sharing a type of mental state or about sharing a single token state. Whether we are talking about type-sharing or token-sharing can make a big difference, because they imply different metaphysical structures. An account of social cognition in terms of type-sharing can assume minds to be discrete, disjunct, and belonging each to a single person. In contrast, a token-sharing view of group minds might see a single token mental state as instantiated by a group of people, who are each in this mental state as members of the group. In the latter case, we are using a stronger sense of sharing. If the mental state in question is a subjective experience, strong sharing would imply that the p-Umwelten of the participants are not closed off from each other, but open, shared, or fused in some way. The difference between weak sharing and strong sharing can also be thought of as the difference between our experiences being qualitatively or numerically identical. This chapter investigates whether phenomenological and enactive accounts of intersubjectivity give us good reason to believe that strong sharing occurs. I argue that they do not, and that the view that p-Umwelten are always closed is in tune with a view of intersubjectivity that can account for the phenomena discussed by enactivists and integrate the analysis of intersubjectivity found in Husserl without relying on strong sharing. 
The way we commonly talk about subjective experience seems to be indexed to the first-person perspective. Throughout my life, I have only had my own experiences, never those of anyone else. This seems to be more than mere contingent fact and depend in some way on the structure of our language and/or the structure of experience itself. Whenever I have an experience, that experience is mine. Saying that someone else has the same experience seems to exploit an equivocation between two different senses of ÒsameÓ, and perhaps two different senses of ÒexperienceÓ as well. Prima facie, it seems difficult to express what exactly it would mean for two people to be token-sharing one subjective experience. Likewise, it seems difficult to specify how we could ever know whether this is taking place. What is the difference between an intersubjective activity which I (falsely) experience as shared in the strongest sense and a true instance of token-sharing? In the breakdown of romantic relationships, we sometimes learn that what felt like token-sharing to one partner was experienced by the other as an experience of affective disconnect, not even type-sharing, but no shared experience at all. Given these difficulties, it seems preferable to me to describe subjective experience as always indexed to a single subject and their first-person perspective (arguably the way oneÕs life unfolds as a stream of consciousness before oneÕs eyes). 
These considerations can be extended to make the case that private individual experience should be the default option or natural starting point for giving an account of social encounters: I wake up in the morning, I put on my shoes, and I walk into the forest. Each of these activities I do by myself, and alone. These particular experiences, right now, are not shared by anyone. The conditions that make it possible for me to have these experiences depend on many other human subjects who built the streets I walk and tend the forest, who made the shoes I put on and sold them to me, who taught me how to tie my shoelaces, and so on. But the experiences as such are mine, and no one elseÕs. They are private not in the sense that no one can see me walk down the street, but in the sense that no one else is having the same experience I am having. This corresponds to the description a closed p-Umwelt in chapter 4 and might be called Ôphenomenologically privateÕ. If we can agree on this, we have established that we have at least a pre-theoretic understanding of what it means to have a solitary experience as an individual. There are kinds of experiences that occur in our lives which are accessible only to the single individual to whom they happen. 
Once we take into account not just solitary activities but also social ones, we are faced with two options: One option is that these experiences are shared in various ways between individuals, but not in the strong sense of multiple subjects partaking in one token experience, as an at least partial melding of their subjectivities or streams of consciousness. A social encounter between myself and another person would then involve each of us having an experience that is in various ways similar to that of the other and shaped by our interactions, yet private in the sense that I only have direct access to my experience and you only have access to yours. On this view, all the manifold kinds of experience I encounter throughout my life can be interpreted as following the same basic logic of Ôone experience, one subject having itÕ. The alternative view is to interpret some social encounters as instances of strong sharing, in which two or more subjects have or access the same single token experience together. On this view, there would be at least two different kinds of experiences that occur in our lives: those that are phenomenologically private and those that are shared in a strong sense. We can also highlight this difference through another contrast: Most of the time, I do not have direct access to the subjective experience of another, nor does it feel like I do. Their subjective experience is phenomenologically private. If there are some situations in which it seems to me as if I have direct access to their subjective experience, does this feeling reveal some metaphysical truth about a drastically different way in which we can have experience, by sharing it in the strong sense? Postulating a second, fundamentally different kind of experience in addition to the phenomenologically private experience of individuals is only necessary if this is the only way to account for the kinds of social encounters we humans have. This would be the case either if some social encounters demonstrably involve strong sharing, or if there are some social encounters that cannot be accounted for in terms of phenomenologically private experience. In this chapter, I will argue against each of these options in turn, by criticizing the arguments developed in favor of strong sharing and by sketching an alternative account of the same social phenomena in terms of phenomenologically private experience. I do not argue that a view that endorses strong sharing is in principle untenable, but rather that based on the available arguments in favor of it and a critical assessment of these arguments, we should prefer an account that only needs to postulate one single kind of experience: the phenomenologically private experience of individual subjects. 
In the philosophy of embodied cognitive science, this problem of what it means to share an experience plays out through the Husserlian vocabulary of Leib and Kšrper, which Merleau-Ponty picked up and developed in his later work into the notion of Ômutual incorporationÕ. An enactive account of intersubjectivity developed by Thomas Fuchs and Hanne De Jaegher (2009) marshals these phenomenological resources to endorse a view that appears to involve strong sharing. I choose their view as the target of my critique in this chapter not in order to demonstrate that it is wrong, but because it illustrate what is entailed in holding a view that relies on strong sharing and contains the most explicit arguments in favor of one within the enactivist literature. Although Fuchs and De JaegherÕs account of intersubjectivity does not use the term Umwelt, it is important for this discussion because it is the most explicit and detailed account in embodied cognition that involves strong sharing, which entails that p-Umwelten are not private and closed. The importance for my overall position on UexkŸllÕs concept of Umwelt is the following: If the Fuchs and De Jaegher view were the only feasible account of some social encounters, the fact that this view describes strong sharing would mean that the p-Umwelten of the subjects engaged in these encounters are not completely closed at least for some time. If an alternative view existed, but the Fuchs and De Jaegher view were preferable because we had strong reasons to believe that strong sharing occurs, UexkŸllÕs claim that p-Umwelten are closed would be facing at least a strong counterargument. My claim in this paper is not that Fuchs and De JaegherÕs view is untenable, but that an alternative view that does without strong sharing is both possible and preferable. 
In order to make my case, I will address the two main sources of support marshalled by Fuchs and De Jaegher: analyses of specific social encounters and references to core thinkers in the history of phenomenology. Of these, I take the analyses of social encounters to carry more argumentative weight. If they demonstrate that strong sharing occurs, the work is done. In comparison, showing that a particular view is in keeping with the views held by core thinkers in a tradition is important for situating the view within that tradition, but carries less argumentative weight unless the important thinkers in question are not merely cited in terms of their views, but as offering specific arguments in support of them. Nevertheless, it may lend some support to my position that I show how a view of social encounters sometimes characterized as ÔintersubjectiveÕ can function without strong sharing and still be in keeping with the phenomenological tradition. 
Section 6.2 of this chapter has four parts: The basic terms in which phenomenologists talk about bodies and their role in experience, the ways in which we might be said to experience not just our own Leib but also the Leib of another, my reading of Fuchs and De JaegherÕs view as entailing strong sharing, and an argument that neither the evidence of our own subjective experience nor the phenomenological philosophy drawn on by Fuchs and De Jaegher provides strong support for strong sharing. In section 6.3, I broaden the question of whether phenomenological analysis demonstrates strong sharing. I discuss Dermot MoranÕs account of intersubjectivity in Husserl and Merleau-Ponty, which seems to interpret them as endorsing strong sharing, and argue that neither of the two thinkers obviously endorses strong sharing and that Husserl, in the passages cited by Moran, should be read as excluding strong sharing from this account of transcendental intersubjectivity. In the last section before the conclusion of this chapter, I offer an alternative account of embodied intersubjectivity that can explain all the relevant phenomena without appealing to strong sharing. The upshot of this chapter is that neither the social phenomena of our personal lives nor a phenomenological analysis of intersubjectivity require us to posit strong sharing, but can be accounted for within a view on which p-Umwelten are closed. 

6.2 An enactive account of intersubjectivity as strong sharing 
In this section I outline my reading of the enactive account of intersubjectivity developed in Thomas Fuchs and Hanne de JaegherÕs (2009) essay ÒEnactive intersubjectivity: Participatory sense-making and mutual incorporation. I set the stage for this by introducing the phenomenological distinction between Leib and Kšrper [lived body and living body] and by discussing in what sense one can experience the Leib of another person, according to Husserl. I then present my reading of Fuchs and de JaegherÕs view as an instance of strong sharing and defend it against one of two possible objections. 
6.2.1 The phenomenology of bodily experience 
HusserlÕs distinction between Leib and Kšrper is often translated as a lived body and a living body. A lived body denotes Òa living subject of experienceÓ as well as its Òsubjective experience of its bodily existenceÓ (Thompson 235, 231), while a living body is a Òphysical living bodyÓ, and thus a Òmaterial thingÓ (Thompson 231, 235). This translation is not quite universal, the distinction is e.g. also described in English as the difference between Òa perceived external body [Kšrper] and my own bodily organism [Leib]Ó (Bernet, Kern & Marbach 7). This latter formulation highlights the fact that while every human being I perceive, including myself, has a Kšrper, since I only experience the world through my own body, I only immediately experience myself as Leib. This intrinsically perspectival nature of Leib is sometimes included in its very definition, as the Òspecifically human body as we experience it first-personallyÓ (KŠufer & Chemero 2015: 99). 
In the first person, my Leib is given as subject and object at the same time. When one of my hands touches the other, I am simultaneously the subject and the object of this double sensation of Òself-palpationÓ, of touching and being touched (Taipale 49). In this experience, the Leib functions in two ways, as ÒÕlived bodily interiorityÕ (Innenleiblichkeit) and Ôlived-bodily exteriorityÕ (Aussenleiblichkeit)Ó (Taipale 52). These correspond to the difference between being a body and having a body. Being a body denotes the embodied manner in which I am open to my environment and experience it through my Leib. Having a body refers to the constitution of my own body within my experience, which, since it is something I experience, already presupposes being a body (Taipale 52-53). Insofar as ÒÕ[g]ivennessÕ sums up the view that all experience is experience to someone, according to a particular manner of experiencingÓ, Leib is the animate body as it is given to the living subject that is this body (Moran 2000: 11). Based on this definition, if we assume that I only ever experience my own experience, and since your Leib is an aspect of your subjective experience, it seems that I can never experience your Leib, only your Kšrper. 
One possible objection here might be that enactivism draws more directly from Merleau-Ponty than it does from Husserl, and that Merleau-Ponty emphasizes intersubjectivity. Merleau-Ponty expanded on HusserlÕs concepts of Leib and Kšrper, starting at a time when HusserlÕs own account of them in Ideas II had not even been published yet but still lay dormant in the archives at Leuven, where Merleau-Ponty accessed it (Bernet 44). Even though Merleau-Ponty Òfrequently cites a passage from the Crisis whereby Husserl claims that transcendental subjectivity is an intersubjectivityÓ2 Merleau-Ponty, at least in his classical Phenomenology of Perception, before the ontological turn of his later work, also emphasizes the primacy of oneÕs own perspective in oneÕs experience of the world: ÒMerleau-Ponty even speaks in this connection of a lived solipsism that remains insurmountableÓ (Zahavi 157). ÒI can never live the presence of an other in the way in which the other lives this presence, i.e. I can never experience the other in the same way in which I experience myself Ó (Zahavi 157). 

6.2.2 The Leib of the Other 
According to Dermot Moran, ÒHusserl did not appear to think I could grasp the other self or person immediately and fully, in an originary mannerÓ, which is to say not quite in the same way in which I grasp myself as Leib (177). However, Husserl did develop an account of how ÒI experience 
2 Moran (2000) points out that this quote is not to be found in the Crisis and distorts HusserlÕs position (178). 
the other as another body like myself Ó Òon the basis of something like an analogyÓ (Moran 177). This process of drawing on my own experience as Leib to perceive the other also as Leib is called mediate apperceptive transference. In Sara HeinŠmaaÕs pithy summary: 
ÒHusserlÕs solution to the problem of other living bodies rests on his idea of transfer 
of sense. He argues that the experience of localized sensations and the primitive sense 
of living as sensing is transferred over from oneÕs own body to other bodies in the 
environing spaceÓ (HeinŠmaa 227). 
When I perceive an Òexternal body [Kšrper]Ó which displays a similarity to my Òbodily organism [Leib]Ó, ÒI perform an apperceptive transferenceÓ in which ÒI apprehend the external body as a sensing and perceiving bodyÓ Òin analogy with my own bodily organismÓ (Bernet, Kern & Marbach 160). ÒMy own experience gives me the possibility of understanding that there are other possible viewpoints on experienceÓ (Moran 177).3 This transference is not an intellectual or conscious act, but happens Òwith one glanceÓ (Bernet, Kern & Marbach 160). The Òtransference of senseÓ from my Leib to that of the other in this apperception is similar to the way in which I perceive a pair of scissors as having the function of cutting by transferring my past experience with scissors onto each new pair I encounter (Bernet, Kern & Marbach 160). Yet it is dissimilar from it in that the object of comparison is my Òown bodily organismÓ which Òis always there along with the otherÓ (Bernet, Kern & Marbach 160). 
In summary, the Leib of the other is not given to me in its lived-bodily interiority, nor in the perpetually ongoing double sensation of self-palpation, but instead as the product of my own mediate apperceptive transference. This matches MoranÕs assessment of the difference between the two ways in which Leib is given: Òthe experience of the other [É] is an experience of a kind of givenness which is always marked as non-original, that is as not lived through in a primordial fashion by myself Ó (Moran: 177). This is crucial: We now have two scenarios in which Leib characterizes a body that is given to oneÕs experience, but depending on whether this body is oneÕs own or someone elseÕs, its givenness is radically different. Since through the epoch. Òthe world and its objects may only be [É] 
3 We might well ask how strong the inßuence of this account was on Hans JonasÕ assertion that Òlife can be known only by lifeÓ, which is similarly built on the idea that Òevidence of each oneÕs own organic awarenessÓ underpins our experience of the bodies of other living beings as Òexternal manifestation of the inwardness of substanceÓ (91). 
investigated as recollected, perceived, imagined, judged, valuedÓ, the mode in which they are recollected, perceived, etc., is of primary importance (Zahavi 4-5). 
To clarify usage, I argue that the difference in how first-person and second-person Leib are given should be marked: LeibS (Leib for oneself) is oneÕs own Leib, which spans open the world of experience through its lived-bodily interiority and which one experiences in double sensation, while LeibO (Leib of an other) is the Leib of another that one experiences through a process of mediate apperceptive transference. Importantly, any particular personÕs experience contains both kinds of Leiber, in oneÕs experience of oneself and of others, but every person is also experienced as each of these two kinds of Leib, by oneself and by others. Your Leib, as I experience it through mediate apperceptive transference is a LeibO and is given to me in a different way than the one in which your LeibS is given to you. Whether or not your LeibS in your experience and your LeibO in my experience are token identical is an open metaphysical question, but the centrality of the mode of givenness of any object for phenomenological analysis suggests that they are at least not identical for phenomenological investigation: LeibS and LeibO are given in two different ways, to two different people. Part of the perspectival nature of experience is this asymmetry: LeibO logically depends on LeibS, but the reverse is not the case. The concepts of LeibS and LeibO will be deployed to amend or clarify an enactive-phenomenological account of intersubjectivity presented in the penultimate section of this chapter. 

6.2.3 Mutual incorporation as strong sharing of bodily experience 
In their account of phenomenological-enactive intersubjectivity, Fuchs and De Jaegher (2009) describe the role that embodiment, specifically in the form of mutual incorporation, plays in participatory sense-making. In their analysis of the latter, they show that our focus must be on the process rather than its participants, and that the interaction cannot be reduced to the individuals that make up its parts. This yields two central points: 
1. 
The process of interaction starts to trump the individual intentions of the participants, who increasingly act according to the dynamics of the evolving situation rather than any preexisting plans. 

2. 
The meaning of the situation is not constituted by a summing or comparison of individual interpretations, but emerges from the interaction itself. 

3. 
This is experienced Òas a mutual incorporation, i.e. a process in which the lived bodies of both participants extend and form a common intercorporalityÓ (Fuchs & De Jaegher 2009: 465). 


The first two of these points, about the primacy of the interactive process and the social generation of meaning, are not the target of my critique. My focus here is on the third claim, which seems to involve strong sharing of experience, and on the experience of the body as Leib within this process. My contention is that even in the most tightly coupled intersubjective encounters, the phenomenology of Leib and Kšrper still has to be thought as consisting of two perspectives proper to the two participants, which are each asymmetrical but both coupled to each other symmetrically within the interaction. But before I make my case, I need to establish that Fuchs and De Jaegher are best understood as advancing an account of strong sharing. 
There are two ways to conceptualize the moment when Òthe otherÕs body reaches out to my own, and my own reaches out to the otherÓ (Fuchs & De Jaegher 476). In the strongest possible reading of intersubjective embodied experience, the experience itself stems from the process of interaction. There is only one source of embodied experience, and it is immediately and originally unified. The process itself has embodied experience, and the two human beings that are interacting partake in this common, emergent embodied experience. Call this process experience. In contrast to this, I argue that it only makes senseÑwithin the phenomenological method but also more generallyÑ to speak of the experiences of each participants, which are coupled and aligned in a particular way during the process of interaction. Call this participant experience. Since the former view involves both participants having the same token experience, process experience involves strong sharing. On the other view, the process of social coordination merely results in the two subjects undergoing qualitatively identical, yet distinct, episodes of participant experience; they are sharing an experience in the weak sense. 
At various points, Fuchs and De Jaegher make statements that could be read as supporting either of these two options. Sometimes, they appear to be describing process experience: ÒThe emerging affect during a joyful playing situation between mother and infant may not be divided and distributed among them. It arises from the ÔbetweenÕ or from the over-arching process in which both are immersedÓ (479). But when they write Òthat each of the partners, while interacting, implicitly experiences or explicitly realises the commonly generated meaning patterns of the interactionÓ, they seem to be talking about two distinct, yet coupled, instances of participant-experience (472). In order to adjudicate between these two readings, we need to focus on the way they describe embodied subjective experience and especially the notion of mutual incorporation. Mutual incorporation builds upon more well-known examples in phenomenology of how a handheld tool or instrument becomes incorporated into a personÕs sense of their own body during skillful use, such as the famous hammer used by Heidegger to explain the difference between ready-to-hand and present-at-hand, or the blind manÕs cane described by Merleau-Ponty (see KŠufer and Chemero 2015). Drawing on Merleau-Ponty, Fuchs and De Jaegher describe how an Òinstrument is integrated into the motor schema like an additional limb or an extension of the body, subjectively felt as ÔmeltingÕ or being at one with the instrumentÓ (2009: 472). When playing tennis, Ò[i]n order to hit the incoming ball properly, the player incorporates its trajectoryÑhe actually moves with the ball from where it starts and feels it approachingÑand thereby adjusts his return to it from the very beginningÓ (ibid. 473). For situations of intensely coupled social interaction, the concept of incorporation is extended into mutual incorporation: 
Ò[A]s a skilled tennis player, I not only incorporate the ball and its trajectory but also my opponentÕs position, posture and movements. I feel the thrust and direction of his stroke as well as the momentum the ball receives, and with this, my own bodyÕs reaction is already being prepared. Here, my lived body is also in an ambiguous state, fluctuating between the incorporated body of the other and my own embodied position.Ó (ibid. 474) 
At this point their account still seems ambiguous in the sense that it is not entirely clear whether mutual incorporation is supposed to involve weak or strong sharing. But there are two points in particular that tip the scales in favor of the strong reading: First, Fuchs and De Jaegher describe mutual incorporation as Òa process in which the lived bodies of both participants extend and form a common intercorporalityÓ (Fuchs & De Jaegher 2009: 465). The important detail here is the singular form of Òa common intercorporalityÓ and the fact that it is formed by the lived bodies of the two (or more) participants. Since the lived bodies are an essential part and aspect of the subjective experience of each participant, postulating their merging into a single entity called ÔintercorporalityÕ seems to imply that they share at least one token experience, this ÔintercorporalityÕ. The second important point concerns Fuchs and De JaegherÕs description of our epistemic situation in infant research: 
Òmutual incorporation and participatory sense-making can provide insight into 
anotherÕs experience, even if the other has no verbal abilities. If intentions, meanings, 
affects and understandings can be created in the in-between and each interactor participates in this, it should be possible to grasp (to a certain extent) the experience of a non-verbal partner by interacting with him. [É] This makes a phenomenology of infantsÕ experience conceivable.Ó (ibid. 482) 
A Òphenomenology of infantsÕ experienceÓ would seem to require direct access to their experience, rather than e.g. an external investigation of their facial and bodily expressions. This at least seems to follow from core features of how phenomenology is defined as: 
Òthe study of human experience and of the ways things present themselves to us in and through such experienceÓ (Sokolowski 2000: 2, cited in Seamon 2019: 46) 
Òthe study of phenomena as experienced by human beings. The primary emphasis is on the phenomenon itself exactly as it reveals itself to the experiencing person in all its concreteness and particularityÓ (Giorgi 1971: 9, cited in Seamon 2019: 46). 
Òthe study of experience, particularly as it is lived and as it is structured through consciousnessÓ (Friesen, Henricksson, and Saevi 2012: 1, cited in Seamon 2019: 46). Or Òan attempt to understand from the insideÑand not to dismiss or criticize from the outsideÑthe whole spectrum of experienceÓ (Vesely 1988: 59, cited in Seamon 2019: 46). 
Since the infants have no way of reporting their experience to us verbally, the only way that it might be possible for us to perform a phenomenological analysis of it seems to be if we were to directly have access to the same experience, i.e. if we share it in a strong sense. 

6.2.4 The case against strong sharing 
I do not claim that strong sharing is in principle impossible, since I think that whether or not we deem it possible depends on metaphysical commitments, rather than anything resembling Ômetaphysical factsÕ which we could somehow Ôfind out aboutÕ. At the end of this chapter, I will outline an alternative account of intersubjectivity that allows us to avoid the metaphysical commitments necessary for strong sharing. In this section, I offer a methodological critique instead: We have no good way of determining (phenomenologically or, to my knowledge, otherwise) whether episodes that we experience as shared really are shared in the strong sense. To motivate this discussion, consider the following scenario: 
You are sitting in a train that pulls up to the final station. As you stand at the door ready to exit, you gaze out of the window and impatiently scan the faces in the crowd for your beloved partner, whom you have not seen in weeks and miss dearly. You cannot wait to hold them in your arms and anticipate this first embrace so intensely that you can almost feel it in your body. Then the train stops, you hear the metallic sound of the door lock disengaging and climb down onto the platform. In between the bodies of strangers, you spot your lover and rush to them. When you finally embrace, the anxiety and loneliness melt off you, your chest opens, your back and shoulders relax, and your awareness of the platform, train, and crowd recedes completely. In the joy and warmth of your reunion, even the difference between the two of you seems to dissolve, as you press yourself against your partner and feel their love for you just as you feel your own for them. There is no question in your mind that your partner feels the same, and this feeling which fills not just your body and mind, but your entire awareness, seems to be just one experience that you both share. However, after the cab ride home and the climb up the stairs to your shared apartment, your world comes crashing down: Your partner reveals to you that they have fallen out of love, and they break up with you. 
Clearly, in retrospect it seems unlikely that your partner felt exactly the same way you did when you embraced on the platform. What this thought experiment shows is that even in intersubjective situations which we perceive as involving the strong sharing of an intense emotional and bodily experience, this feeling alone does not guarantee that our experience is qualitatively identical to that of the person we feel so intensely connected with, as if our Òlived bodies [É] extend and form a common intercorporalityÓ. If my experience itself cannot guarantee that the other person has a qualitatively identical experience, how could it possible give me a good reason to believe that my experience and the experience of the other are numerically identical? 
The problem is how a social encounter could serve as evidence of strong sharing in principle. Normally, as I go about my life, both my own subjective experience and the subjective experience of others around me are phenomenologically private. But there are also some social encounters that some people describe as feeling like they involve strong sharing, either because the separation between the two (or more) subjects partly dissolves, so that it feels as if their minds and/or bodies temporarily form a single entity, or because what one is experiencing includes an overwhelming feeling that the other is experiencing the same. To be clear, this does not have to include everything that I am experiencing in a given moment, but could just refer to some part of my experience which it feels to me as if the other is sharing. From this feeling, some may want to infer that strong sharing is really taking place. There are two problems with this inference: We do not know whether the other person is really feelings something qualitatively identical, and even if they were, we would have no way of knowing whether this experience is numerically identical with our own. 
The episode described above illustrates that we can have an overwhelmingly strong sense that the other person is having the same feelings that we are having, despite this not being the case. By itself, the fact that we can sometimes be wrong about this does not mean that we are never right. However, it does mean that in any given instance, we cannot be sure whether our feeling that the other is sharing part of our experience (qualitatively or numerically, i.e. either in a weak or strong sense) correctly informs us about the real experience of the other, or whether it misleads. This is the case because the experience in both cases feels the same, i.e. the informative and the misleading versions of this experience are qualitatively identical, the difference in their epistemic status stems not from anything in our experience, but from what the other is experiencing. Even though it seems plausible that our social experiences exist on a scale of qualitative similarity such that some of them involve others having an experiences that is at least in part qualitatively identical (or almost identical) to the one we are having, this does not give us a robust method for determining in any given situation whether this is the case. Beyond our immediate physical and social surroundings, our experience is also shaped by our personal history, the development of our thoughts and feelings, and other factors which can influence whether someone else is undergoing an experience qualitatively identical to ours, but which are not epistemically accessible to us in that moment. If something is numerically identical with itself, it is also qualitatively identical with itself. Conversely, if two experiences are possibly qualitatively different, they are also possibly numerically non-identical. But even if we could ascertain that our experience is qualitatively identical to that of the other, we would have to make a further inference to arrive at strong sharing. 
Imagine a Groundhog Day scenario. You are trapped in a time loop, every morning starts in the same way and you experience everything the same way you did yesterday. In this scenario, you would be having qualitatively identical experiences every morning, but they would be numerically non.identical. Instead, they would be countably many distinct experiences, and their number would equal the length of the Groundhog Day scenario counted in days. Similarly, even if two subjects were engaged in a social encounter in which (part of) their experiences are qualitatively identical, their experiences could still be numerically distinct. We can imagine, abstractly, two different scenarios: In both cases their experiences are qualitatively identical, in both cases it feels to each of them as if they are connected in the most direct and profound way they could imagine, yet in one case they are sharing a token experience, while in the other case their experiences are merely qualitatively, but not numerically, identical. The problem is that from the lived perspective of each of them, there is nothing about the content or character of their experience that could indicate which of the two scenarios they are in. This is a problem specifically for phenomenology, as the study of subjective experience itself. However, it is not clear that any other principled method for determining which of the two scenarios obtains, either. This means that even if we assume that strong sharing is both possible and real, we are still lacking an account of how we might come to know this. 
I do not take this to suggest that strong sharing is impossible, but I donÕt think that this needs to be shown. What I think it shows is that nothing we do (or could) experience in our own lives could, by the evidential strength of the subjective experience alone, reveal itself conclusively as an instance of strong sharing. My criticism of the Fuchs and De JaegherÕs view here is not that strong sharing is demonstrably impossible, but that nothing within subjective experience, and thus nothing within the scope of phenomenological analysis, could provide us with good reasons to believe that strong sharing occurs. However, if I am reading Fuchs and De Jaegher correctly as implicating strong sharing, the sources they cite in support of their view also have to be considered. 
First, even though Merleau-PontyÕs late work places an emphasis on intersubjectivity and deploys a series of terms including the Ineinander, the chiasm, and the flesh in order to describe how individual subjects are not isolated atoms but instead implicated in each other and the world, it is not clear that his needs to be understood as strong sharing (on intersubjectivity in late Merleau-Ponty see Feiten, Holland, and Chemero 2020 and Benevides, Feiten, and Chemero 2023). Fuchs and De Jaegher cite Merleau-Ponty on Òintercorporality [É] as the basis of social understandingÓ describing it Òas if the other personÕs intentions inhabited my body and mine hisÓ (Merleau-Ponty 1962: 215, cited in Fuchs & De Jaegher 2009: 475). The crucial point for us is the phrase Òas if Ó, which seems to indicate that this is not an instance of strong sharing. Similar doubts can be raised about the support for strong sharing in Merleau-PontyÕs late work. Building on HusserlÕs account of how, when I touch one of my hands with my other hand, there is a ÒÔreversibilityÕ and ÔencroachmentÕ between the sentient and sensible aspects of the bodyÓ, Merleau-Ponty extends this ÒchiasmÓ into an analysis of intersubjectivity (Toadvine 2012: 340). Even though Merleau-Ponty maintains that there is likewise Òa kind of reversibility obtains between the sensing body and the worldÓ (ibid. 340), as well as between bodies, and that Òthe chiasm of the body, consequently, can be generalized to all beingsÓ (ibid. 342), this reversibility is never complete but always Òcharacterized by a gap or divergence (Žcart)Ó (ibid. 340.341). I am not arguing that Fuchs and De Jaegher fail some standard according to which their interpretation of Merleau-Ponty has to be the only possible one. What I am arguing is that since Merleau-Ponty describes intercorporality using the phrase Òas if Ó in one of the central quotes employed by Fuchs and De Jaegher, an appeal to Merleau-PontyÕs view has less argumentative weight than it would if supported by quotes that more explicitly endorse strong sharing. 
Second, Fuchs and De Jaegher Òagree with Sheets-Johnstone (1999) when she suggests that a constructive phenomenology of infant experience is possibleÓ (2009: 482). This conception of a Òconstructive phenomenologyÓ is outlined in Chapter 5 of Sheets-JohnstoneÕs (2011) The Primacy of Movement and involves Òdraw[ing] upon our own adult experiences of newborn infants, upon our experiences of self-movement [É] and upon scientific studies that illuminate the significance of self-movement in infancyÓ (Sheets-Johnstone 2011: 212). Importantly, none of these methods involve direct access to, or sharing of, the experience of infants. It is not important for this discussion whether this methodology really amounts to a phenomenology of infant experience, what matters instead is that it neither requires nor lends support to the claim that humans share experiences in the strong sense. 
There are two main objections that might be raised against my critique of Fuchs and De Jaegher (2009). First, one might argue that I misread Fuchs and De Jaegher and that their account only involves weak sharing.4 Alternatively, one might argue that their account does involve strong sharing and is right to do so, since phenomenology is not as individualistic as I have made it seem, and support for the notion of strong sharing can be found e.g. in the works of Husserl and/or Merleau-Ponty. I will briefly address the first objection here and tackle the second objection in more detail in the next section. 
In their description of intersubjectivity, Fuchs and De Jaegher highlight that Òinteractional coordination does not necessarily imply perfect synchronizationÓ but rather involves Òthe continuous fluctuation between synchronised, desynchronised and in-between states that drives the process forward. The to-and-fro between attunement and alienation is even necessary in order to understand each other without melting into each otherÓ (2009: 471). This is in keeping with the broader enactive line on intersubjectivity, expressed e.g. in Linguistic Bodies, where Ezequiel Di Paolo, Elena Cuffari, and De Jaegher emphasize that Òdespite the rejection of methodological individualism, [É] social interaction as we have defined it fundamentally involves the continued autonomy of its participantsÓ (2018: 83-84). Despite this, I still think that my reading is the most plausible one, since I do not see any way to interpret the description of Òmutual incorporation [as a] process in which the lived bodies of 
4 Caner Yildirim makes this objection in his unpublished commentary on my paper ÒWhat do we share when we share a bodily experience?Ó, delivered at the Annual Gathering of the Southern Society for Philosophy and Psychology 2023. 
both participants extend and form a common intercorporalityÓ, which is central to the view advanced by Fuchs and De Jaegher, as anything other than strong sharing (Fuchs & De Jaegher 2009: 465). 
Even if my reading of Fuchs and De Jaegher as advocating strong sharing is wrong, my arguments here can still fulfill their main function. My goal here is not to prove Fuchs and De Jaegher wrong, but instead to show that the notion of strong sharing does not enjoy strong support from phenomenological analyses, and thus that phenomenology does not provide strong reasons to think that p-Umwelten are open. Therefore the second objection, according to which phenomenology does lend credible support to an account of strong sharing, is the more important one for my project and I will consequently address it in more detail. 


6.3 Does phenomenological analysis reveal strong sharing? 
A key feature of the way we encounter our environments can be described as ÔvalenceÕ. Objects, spaces, and people are not neutral entities made up only of shapes, colors, and textures, instead we immediately perceive them as meaningful in various ways. Some rooms we perceive as spaces to linger in and work, rest, or socialize, other rooms we perceive as spaces to pass through, or to perform some action and leave, such as buying something, waiting for oneÕs turn, use the bathroom, etc. This insight is shared by ecological psychology and phenomenology. Importantly, perceiving an entity as something does not make it so. We can visit a haunted house and perceive its contents and contexts as threatening or dangerous, even though they are not. The same is true for an analysis of how we experience situations of intense social connection. We may experience something as shared in the strong sense, but that does not guarantee that this character of our personal experience informs us reliably about the (metaphysical) relationship between this experience and the experience of the other person involved. One way to phrase this problem is that there is no direct and reliable indicator within the content or structure of any particular experience that allows us to distinguish between Ôexperience asÕ and Ôexperience as if Õ. During the course of our lived experience, we often find out only later which kind of experience it was, as in the loversÕ reunion on the train platform described above. Central to the phenomenological analysis of such experiences in both Husserl and Merleau-Ponty is the German term Ineinander [literally in one another], translated as ÔinterpenetrationÕ (Moran 2015: 110). The basic question that I want to discuss here, which has direct implications for the epistemic status of phenomenology as a method and for the question of whether p-Umwelten are open or not, is this: Can the experience of interpenetration be evidence of the interpenetration of experience? 
One scholar of phenomenology who seems to endorse an account of intersubjectivity as strong sharing is Dermot Moran, both in the editorsÕ introduction to the (2015) volume Phenomenology of Sociality: Discovering the ÔWeÕ he co-edited with Thomas Szanto and in his ÒIneinandersein and LÕinterlacs: The Constitution of the Social World or ÒWe-WorldÓ (Wir-Welt) in Edmund Husserl and Maurice Merleau-PontyÓ in that same volume. It is often difficult to determine with absolute certainty whether a position endorses strong sharing, even if it places heavy emphasis on the fundamental role of the social for human subjectivity and consciousness, so it will help to give an impression of the general tone of MoranÕs position before focusing on specific details. The editorial introduction co.authored with Szanto is very useful for this purpose because it provides an account of how they conceive of phenomenology as a philosophical project, which can be contrasted with the perspective that has emerged from my reading of UexkŸll. 
UexkŸllÕs emphasis on the worlds of individual subjects and his belief that the Umwelt of each human person is closed can be described as a form of Ômethodological individualismÕ. The same is true for my above comments about phenomenology as a method for systematically investigating subjective experience and my ensuing skepticism about its ability to produce evidence of strong sharing. In contrast, Moran and Szanto set out to dispel any individualistic interpretation of phenomenology and argue that an emphasis on sociality has always been present in phenomenology as a philosophical project: 
ÒPhenomenology, from its very inception and for systematic reasons, was always synonymous with the phenomenology of sociality, the careful descriptive elucidation of the layers and strata of both social and collective life. Moreover, [É] a great number of phenomenologists, even if certainly not all, would concur with the idea that sociality is not only a matter of intersubjectivity, of relations between subjects, in the sense of you and me appropriately interacting, but also of me, or me and you, relating to a ÔWe,Õ or forming an us [É]Ó (Szanto and Moran 2016: 2). 
Against this backdrop, we can assess two kinds of indicators in this introduction which suggest that the authors endorse strong sharing and prime us to conceive of strong sharing as a likely interpretation of MoranÕs single-authored essay in the same volume. While the second of these indicators is positive, the first is negative, i.e. it suggests that they endorse strong sharing because of what they reject: 
ÒIn factÑand contrary to still widespread prejudicesÐÐit is entirely wrong to conceive of phenomenology as practicing any form of methodological individualism, let alone solipsism. Rather, phenomenology has always recognized that humans come to develop their intentional, meaningful, and meaning-constituting lives always and only in the context of a given socio-historical context, a common background, or a set of shared habits, and embedded in a world in which they participate, and which they possibly aim to individually or collectively transformÓ (Szanto and Moran 2016: 2). 
At first glance, these comments seem to be in contradiction with Dan ZahaviÕs account of Merleau-Ponty, Ò[who] even speaks [É] of a lived solipsism that remains insurmountableÓ (Zahavi 157). ÒI can never live the presence of an other in the way in which the other lives this presence, i.e. I can never experience the other in the same way in which I experience myself Ó (Zahavi 157). This seems like it should qualify as at least some form of methodological individualism, and thus in contradiction with Szanto and Moran, who rule out any form of methodological individualism for phenomenology. Even in the same volume that this is the introduction to, Stewen CrowellÕs essay on ÒSecond Person PhenomenologyÓ opens like this: 
ÒBy Ôsecond-person phenomenology,Õ I mean phenomenological reflection on the experience of being addressed by a claim, experiencing oneself Ôin the accusative,Õ as it is sometimes described. Thus, second-person phenomenology is, like all phenomenology, a reflection on first-person experience [É]Ó (Crowell 2016: 70). 
Technically, Òfirst-person experienceÓ might also refer to the first-person plural, but the default reading when the grammatical number is omitted is singular, and the reference to Òoneself Ó supports this. Crowell seems to be endorsing some form of methodological individualism about phenomenology here, and his comments are in keeping with the very basic idea that one only ever has oneÕs own experiences, so a systematic direct analysis of experience is necessary an analysis of oneÕs own experience. It is also helpful to consider in detail the exact claim made by Szanto and Moran in the above quote by breaking it up into its components: 
A) Ò[É] it is entirely wrong to conceive of phenomenology as practicing any form of methodological individualism, let alone solipsism.Ó ÒRather,Ó 
B) Òphenomenology has always recognized that humans come to develop their intentional, meaningful, and meaning-constituting lives always and only in the context of a given socio-historical context [É]Ó (Szanto and Moran 2016: 2). 
The word ÒratherÓ generally connects two claims, repudiating the first and endorsing the second. Additionally, it seems to imply that there is some further logical or causal connection between the two, such that for example the first claim must be false because the second is true. Daniel Dennett has coined the phrase ÒratheringÓ to describe formulations that seem to imply that two claims are mutually exclusive, even though they are not (Dennett 2011). The upshot of my arguments in this chapter is that phenomenology can be methodologically individualist (in some sense) while also endorsing the view that humans and their minds develop entirely in social settings and ways, and even generating the insight through its own methods that the character of each individualÕs subjective experience is that of being oriented towards one single social world shared with all other humans. Subjective experience can be something that individuals have in fundamentally private p-Umwelten, even if these subjects are necessarily social and if these p-Umwelten are experienced as essentially social and intersubjective. Supporting this claim involves arguing against MoranÕs account of intersubjectivity in Husserl and Merleau-Ponty. 
In addition to the repudiation of methodological individualism, the description of MoranÕs essay giving in the introduction also indicates that he endorses strong sharing, since one of the core aspects of his essay is described here as the Òinterpenetration of subjective consciousnessesÓ (Szanto & Moran 2016: 13). In the essay, Moran explains how Husserl and Merleau-Ponty, drawing on HusserlÕs work, conceive of the Òintersubjective constitution of ÔsocialityÕÓ, both using the term ÒIneinanderseinÓ (Moran 2016: 108). ÒThe experienced surrounding world, for Merleau-Ponty, as for Husserl, is a distinctly human Welt that is much more complex than the ÔUmweltÕ(milieu) of animalsÓ (Moran 2016: 112). This might suggest that the phenomenologists consciously avoid using the term Umwelt for humans in order to underscore their special status, but this is not the case. Husserl, in a passage cited by Moran, refers to our common social world as Òcontinually and quite obviously there as a common world surrounding us all (als eine uns allgemeinsame Umwelt); obviously thereÑit is the directly tangible and visible world [which] embraces not merely things and living beings, among them animals and humans, but also communities, communal institutions, works of art, cultural establishments of every kindÓ (Hua VII, 280, cited in Moran 2016: 111). For Merleau-Ponty, the term Umwelt is even more central and appears in crucial passages during his later work where he discusses the Ineinander alongside the related notions of the chiasm and the flesh (see Feiten, Holland, and Chemero 2020 and Benevides, Feiten, and Chemero 2023). 
According to Moran, ÒHusserl maintains that self-consciousness and the consciousness of others in the context of an overall ÔintersubjectivityÕ are inseparableÓ (Moran 2016: 117). The crucial question for us is whether Òconsciousness of othersÓ here means my consciousness of others or their own consciousness. Only the latter meaning would support a notion of intersubjectivity that involves the actual Òinterpenetration of consciousnessÓ and therefore strong sharing and open p-Umwelten. In contrast, if Husserl means that my self-consciousness is inseparable from my consciousness of others, this is not an instance of strong sharing. One of the passages that most strongly seems to indicate that Moran is really attributing strong sharing to HusserlÕs thought is his description of HusserlÕs account of Òthe intersubjective joining together of subjects, which he calls, borrowing from Leibniz, the Ôcommunity of monadsÕ (Gemeinschaft der Monaden)Ó (Moran 2016: 108). Central to MoranÕs reading is ¤56 in the fifth of HusserlÕs Cartesian Meditations (1960/2012): 
As Husserl makes clear in the Fifth Cartesian Meditation ¤56, there is a real communion between subjectivities, although each subject is, in HusserlÕs Leibnizian formulation, a ÔmonadÕ and thus an absolutely separately existing self, and at the same time, Ô[s]omething that exists is in intentional communion with something else that exists. Itis an essentially unique connectedness, an actual community and precisely the one that makes transcendentally possible the being of a world, a world of humans and thingsÕ (CM ¤ 56, 129; Hua 1, 157)Ó (Moran 2016: 118). 
This sounds like strong sharing, so it is worth considering the relevant passage in Husserl in detail. In ¤56, Husserl gives an account of the kind of intersubjectivity that is generally at issue in the enactive and phenomenological accounts discussed in this chapter, and a careful analysis of what he says here shows it to be not an account of strong sharing, but an account of how it is that an individual human beings perceives others as connected to themselves, and themselves as connected to others, within their own experience, i.e. within their p-Umwelt. 
First, Husserl recapitulates: ÒThe only conceivable manner in which others can have for me the sense and status of existent others, thus and so determined, consists in their being constituted in me as others [Da§ die Anderen sich in mir als Andere konstituieren, ist die einzig denkbare Weise, wie sie als seiende und soseiende fŸr mich Sinn und Geltung haben kšnnen]Ó (Husserl 1960/2012: 128). This condition for having the Òsense and status of existent othersÓ is simultaneously a condition for showing up in my experience, i.e. an epistemological and methodological condition which has to be met in order for others to become the object of phenomenological study. 
Next, Husserl draws a contrast, explaining how despite the fundamental separateness of the experiences of two distinct subjects, the communion of monads is not naught or illusory either: 
ÒTo be sure, they are separate from my monad, so far as really inherent constituents are concerned, since no really inherent connexion leads from their subjective processes to my subjective processes or from anything included in their peculiar ownness to anything included in mine. [É] On the other hand, this original communion is not just nothing. Whereas, really inherently, each monad is an absolutely separate unity, the ÔirrealÕ intentional reaching of the other into my primordiality is not irreal in the sense of being dreamt into it or being present to consciousness after the fashion of a mere phantasy. [Zwar sind sie reell von der meinen getrennt, sofern keine reelle Verbindung von ihren Erlebnissen zu meinen Erlebnissen und so uberhaupt von ihrem Eigenwesentlichen zu dem meinen ŸberfŸhrt. [É] Andererseits ist diese ursprŸngliche Gemeinschaft nicht ein Nichts. Ist jede Monade reell eine absolut abgeschlossene Einheit, so ist das irreale intentionale Hineinreichen der anderen in meine PrimordialitŠt nicht irreal im Sinne eines HineingetrŠumtseins, eines Vorstellig-Seins nach Art einer blo§en Phantasie.Ó (Husserl 1960/2012: 128-129) 
The last sentence of this quote is directly followed by the one quoted by Moran above on Òintentional communionÓ. This bit of context is already helpful in interpreting MoranÕs point. The part that concerns what we might call the metaphysics of experience insofar as it pertains to the individuation of subjects comes first: each individual only has their own experience, and there is no direct connection between them in the sense of an Òinterpenetration of consciousnessÓ or the opening of a p-Umwelt. Despite this, Husserl clarifies that our sense of communion with each other is not merely a mirage. The point of ¤56 as a whole is to identify this kind of intersubjectivity as a fundamental aspect of how the world and the people in it appear to usÑin each of our p-Umwelten, we might add. 
In the rest of this section, Husserl makes it even clearer that this form of intersubjectivity is an aspect of each individualÕs own experience and nothing like a metaphysical melding of subjectivities, with helpful references to both the role of the body in experience and the constitution of our world (or Umwelten): 
ÒIf, with my understanding of someone else, I penetrate more deeply into him, into his horizon of ownness, I shall soon run into the fact that, just as his animate bodily organism lies in my field of perception, so my animate organism lies in his field of perception and that, in general, he experiences me forthwith as an Other for him, just as I experience him as my Other. [Dringe ich, mich in ihn einverstehend, in seinen Eigenheitshorizont tiefer ein, so werde ich bald darauf sto§en, da§, wie sein Kšrper-Leib in meinem, so mein Leib sich in seinem Wahrnehmungsfeld befindet und da§ er im allgemeinen mich ohne weiteres so als fŸr ihn Anderen erfŠhrt, wie ich ihn als meinen Anderen erfahre.Ó (Husserl 1960/2012: 129-130/129). 
We must be careful here not to misinterpret the character of this ÔpenetrationÕ. The German ÔeinverstehenÕ means something like understanding-into and since Husserl has already explicitly stated that there is no direct connection between my subjective processes and those of the other, this cannot be read as describing and interpenetration of our fields of subjective experience. Instead, Husserl describes two distinct fields of perception, mine and the other, in which we respectively experience each others body. Towards the end of the section, Husserl makes explicit what he feels should be obviousÑthat insofar as it is present in my experience (and thus insofar as it is the object of a phenomenological investigation I undertake), the community of monads is an aspect of my own subjective experience (and not, for example, a metaphysical bridge between my experience and that of another): 
ÒTo this community there naturally corresponds, in transcendental concreteness, a similarly open community of monads, which we designate as transcendental intersubjectivity. We need hardly say that, as existing for me, it is constituted purely within me, the meditating ego, purely by virtue of sources belonging to my intentionality; nevertheless it is constituted thus as a community constituted also in every other monad (who, in turn, is constituted with the modification: ÔotherÕ) as the same community Ð only with a different subjective mode of appearance Ð and as necessarily bearing within itself the same Objective world. [NatŸrlich entspricht dieser Gemeinschaft in transzendentaler Konkretion eine entsprechende offene Monadengemeinschaft, die wir als transzendentale IntersubjektivitŠt bezeichnen. Sie ist, wie kaum gesagt werden mu§, 
rein in mir, im meditierenden Ego, rein aus Quellen meiner IntentionalitŠt fur mich als seiend konstituiert, aber als solche, die in jeder (in der Modifikation ãAndererÒ) konstituierten als dieselbe, nur in anderer subjektiver Erscheinungsweise konstituiert ist, und konstituiert als dieselbe objektive Welt notwendig in sich tragend.]Ó (Husserl 1960/2012: 130/129-130) 
Seen in context, it seems clear that Husserl is not advancing a view that involves strong sharing, but that what he means by Òtranscendental intersubjectivityÓ is a feature that is common to all human p-Umwelten, without thereby leading them to open up or merge in any sense. Not only does HusserlÕs account not endorse or require strong sharing, but he feels that it hardly needs to be said that this kind of intersubjectivity does not involve strong sharing. 
6.4. Symmetrical asymmetry: embodied intersubjectivity without strong sharing 
We have seen that HusserlÕs description of intersubjectivity does not describe a melding or fusion of two subjectsÕ fields of perception, but rather the mutual presence of each subject in the experience of the other: Òjust as his animate bodily organism lies in my field of perception, so my animate organism lies in his field of perception and that, in general, he experiences me forthwith as an Other for him, just as I experience him as my OtherÓ (Husserl 1960: 130). With each subjectÕs experience, the status of the bodies is asymmetrical: My Leib mediates all of my experience, e.g. the spatial parameters of up and down, front and back, etc., in a way that the body of another does not (Husserl writes ÒLeibÓ for oneÕs own and ÒLeib-KšrperÓ for the body of the other in this passages). However, this asymmetry is equally present in the experience of the other subject, only reversed: In their experience, my body is not the body through which experience is embodied, their own Leib is. On this view, embodied intersubjectivity is asymmetrical on the level of subjective experience and symmetrical when the worlds of experience (p-Umwelten) of two subjects are compared. 
If we express the differences in phenomenological status between the bodies seen under each perspective using the distinction between LeibS (the Leib one has/is oneself) and LeibO (the Leib one experiences another to have/be), this view allows us to account for all the phenomena described by Fuchs and De Jaegher without having to resort to strong sharing. Instead of Òa process in which the lived bodies of both participants extend and form a common intercorporalityÓ, we describe two individual processes of incorporation in the experience of each participant (465). What this means is that I incorporate your LeibO into my LeibS and you incorporate my LeibO into your LeibS, giving us two instances of incorporation that have opposed directionality. We now see an interaction that couples the experiences of two subjects together in such a way that two processes of incorporation which are each asymmetrical are yoked to each other in a symmetrical fashion. 
We can visualize the difference between the two conceptions of intersubjectivity by metaphorically conceiving of incorporation like touching the body of another with oneÕs hand. The hand that touches in this metaphor is oneÕs own LeibS, in the sense in which my lived-bodily interiority makes my experience of the world possible, and the body that is being touched is the LeibO of the other, as which I experience my partner in the interaction. The coupling that is created in participatory sense-making should, on my account, be conceptualized not as a handshake, where two identical elements meet each other in a directly symmetrical union, but as a forearm clasp, where two complex entities each skillfully grasp each other by a part that is not the part which does the grasping (i.e. two beings intentionally grasping each other by their exteriority). 

Leib 
Leib 
Figure 2. Mutual incorporation as Òa process in which the lived bodies of both participants extend and form a common intercorporalityÓ (Fuchs & De Jaegher 465); illustration by Dmitri Akers 

Figure 3. Mutual incorporation as a symmetrical coupling between two asymmetrical processes, each of which involves a subject using its LeibS to grasp another as LeibO; illustration by Dmitri Akers 
In figure 2, two Leiber are reaching out towards each other and uniting in a handshake. The experience of incorporation, represented here by the touch, cannot be assigned to either of the participants. It belongs to the process of handshaking, which is perfectly symmetrical. In contrast, figure 3 shows a forearm clasp that is just as symmetrical on the level of the process. But if analyzed in terms of experience, it decomposes into the experience of the person on the left, who grasps the other as LeibO through their own embodied openness to the world (LeibS), and vice versa for the person on the right. 
Importantly, this gives us an alternative account of intersubjectivity that also proceeds from a phenomenological perspective but that cannot be reduced to a single process of interaction. Instead, it must be expressed in terms of two original conscious beings coming together and forming a coupling in which they grasp each other as Leib but never lose the integrity of their own experienceÑ as their own and distinct from the experience of the otherÑto the unit constituted by the synergistic process. This symmetry of asymmetries also resonates some of the concepts employed in Merleau.PontyÕs later work, as implements both the figure of a chiasm and the idea of reversibility. 

6.5 Conclusion 
UexkŸll thought that p-Umwelten are closed, meaning that each living subject only ever has its own experience, and never the experience of another subject. Nor do two or more subjects share experience in the strong sense of multiple subjects having one single experience. Any account on which subjects sometimes share experience in the strong sense would conflict with UexkŸllÕs view, and conversely, in order to show that p-Umwelten are open rather than closed, one would need to show that strong sharing occurs. The enactive account of embodied intersubjectivity developed by Fuchs & De Jaegher seems to endorse this type of strong sharing, and some of the phenomenological resources they drawn upon appear to lend support to such an account. However, consideration of the kind of evidence present in our subjective experience and a closer reading of the relevant phenomenological philosophy do not yield any reasons that make it necessary to assume that strong sharing occurs. Instead, close attention to HusserlÕs writings on transcendental intersubjectivity shows that his view lends itself to a symmetrically asymmetrical account on which the other shows up in my p-Umwelt and I show up in theirs, without the phenomenal privacy of these two p-Umwelten being breached. The distinction between Leib and Kšrper partly matches that between e-Umwelt and p-Umwelt, insofar as my Leib, like my p-Umwelt, concerns my subjective experience and is thus directly accessible only to myself, whereas the Kšrper or e-Umwelt of a subject are available from an external vantage point for perception and description respectively. 
Chapter 7: Conclusion 
7.1 Umwelt today 
The methodological problems that came to public attention with ÔClever HansÕ are still current today. In discussions about the cognitive abilities of honey bees competing interpretations of the experimental evidence disagree about how the bees solve the task of choosing a card with zero squares over a card with some squares (Howard et al. 2018, Vasas and Chittka 2019). Do the bees have a concept of zero, or are they merely using ÒspeciÞc ßight movements to scan targetsÓ (Vasas and Chittka 2019: 85)? In debates like these, the term Umwelt can help orient our investigation into the lives of animals and caution us against ascribing anthropomorphic abilities that may not be necessary to explain the behavior of the animals in question. Because of its ability to elucidate these issues at the intersection of science and philosophy, Umwelt is a key concept for some animal researchers (e.g. Kremers 2013), but also for scholars in a variety of other Þelds, ranging from theatre studies to embodied cognitive science. 
When using the term Umwelt in our investigations, two factors matter: Does the concept help us think in fruitful ways? And is there a risk that introducing this concept obscures some of the questions it is meant to elucidate? An a.irmative answer to the Þrst question can be derived from the popularity of the term among di.erent groups of researchers. My analysis of UexkŸllÕs use of the term Umwelt answers the second question. By di.erentiating between e-Umwelt and p-Umwelt, we can see how conßating the two senses of the term can create misleading impressions. One of these is the impression that the concept of Umwelt can bridge the gap between the perspective of an external, scientiÞc observer studying an organism and the subjective experience of the organism itself. 
My distinction between two senses of Umwelt achieves the most coherent reading of UexkŸllÕs own writings, but its relevance is not limited to UexkŸll scholars. Instead, the distinction helps us insulate the research of scientists studying the e-Umwelten of animals from philosophical questions about subjective experience. On the side of philosophy, the distinction also shows how various ways in which other thinkers have disagreed with UexkŸll involve di.erent claims and require di.erent kinds of support. Against UexkŸllÕs view that Umwelten are closed, there are many obvious reasons for treating e-Umwelt as open in a temporal sense, such as learning, ontogenesis and phylogenesis. Whether to treat e-Umwelt as open or closed becomes a methodological question that depends on the aims of oneÕs research project. In contrast, the claim that p-Umwelten are open entails that subjective experience is not always private, but that phenomenal experience is sometimes directly shared. The concept of p-Umwelt helps us see how di.icult it is to demonstrate this kind of sharing on the basis an analysis of oneÕs own experience from a Þrst-person perspective, as practiced e.g. in phenomenology. Whenever I experience something, I know that it is part of my p-Umwelt, but the question of whether or not two p-Umwelten are merely temporarily aligned in terms of their qualitative content, or whether they actually intersect in the sense that some part of the subjective experiences of two or more subjects is numerically identical, seems to require a sort of outside perspective that is not available to the subjects themselves. In this way, the distinction between e-Umwelt and p-Umwelt cautions us against conceptual overreach and constrains the kinds of inferences we are licensed to draw both in our scientiÞc investigations of other subjects from an external vantage point and in our phenomenological analyses of our own experience. 
Of course, this view is open to be challenged, and a likely point of contention will be the idea that subjective experience is fundamentally private. I will address two such challenges at least brießy. First, some argue that the notion of private subjective experience should be jettisoned as it cannot be subjected to rigorous scientiÞc investigation and adds nothing to scientiÞc explanations of organisms and their behavior (e.g. Dennett 1988). But the belief that subjective experience as such cannot be measured externally and thus does not lend itself well to being studied in scientiÞc experiments is just what the UexkŸllian view claims as well. Second, it might be argued that subjective experience cannot be fundamentally private because humans are essentially social creatures. This does not follow straightforwardly: It can simultaneously be true that we can only have the kinds of p-Umwelten that we have because we are social creatures, that others play an essential role in the structure and content of our p-Umwelten, and that each of our subjective experience is private and our p-Umwelten closed. It is possible that stronger versions of these challenges can be constructed that are tailored speciÞcally to put pressure on the distinction between p-Umwelt and e-Umwelt (rather than general arguments against 
e.g. qualia, individualism, or solipsism) and I would welcome the opportunity to address these challenges once they are made. 

7.2 Further directions 
There are many ways in which my reading of Umwelt might be fruitful for further research, here I want to very brießy suggest three of them, in the Þelds of embodied cognition, history of 20th century philosophy, and the philosophy of AI. 
For embodied cognition, the distinction between the perspective of an external observer and the phenomenal experience of a subject may be extended beyond uses of the term Umwelt into a more general assessment of its conceptual foundations. Consider the very term ÔembodimentÕ. One important source of this notion was Rodney BrooksÕ work in robotics, where the embodiment in question concerns physical aspects of a robot that are quantiÞable and open to external observation. All of this can be studied without any reference to subjective experience. Another important source of embodiment for cognitive science was the phenomenology of Maurice Merleau-Ponty, where embodiment refers to the way that my own body and my relationship to it shapes my experience of the world, including the way I experience the bodies of others and my own. From this perspective, embodiment is inextricable from subjective experience. Given the risks of conßating e-Umwelt and p-Umwelt, it would be worth undertaking a broader evaluation of the literature on embodied cognitive science to see whether there are also two senses of embodiment at play that can cause conceptual problems when they are falsely conßated. 
In chapter 4, I showed how the distinction between e-Umwelt and p-Umwelt allows us to give a more precise account of various claims that can be made about whether Umwelt is open or closed. Applying this distinction to a detailed reading of one of UexkŸllÕs philosophical commentators has the potential to yield novel insights into the thought of such Þgures as Helmuth Plessner, whose (1928) Levels of Organic Life and the Human: An Introduction to Philosophical Anthropology recently appeared in its Þrst English translation (2019). The philosophical importance of clarifying the relationship between any such Þgure and UexkŸll depends both on the importance of that Þgure overall and on the intensity of their engagement with UexkŸll. In the case of Plessner, the recent translation indicates scholarly interest in his work, and the connection to UexkŸll is substantial enough to recommend such a study. 
Lastly, the recent and dramatic rise of interest in the philosophy of artiÞcial intelligence includes e.orts towards a Ôphenomenology of AIÕ (see e.g. Leib 2024). The analysis I provide in chapter 6 contains the beginnings of a more general account of the epistemic constraints of phenomenological analysis, especially as concerns the generalization of its results to subjects or systems that are very di.erent from the phenomenologist conducting the analysis. Importantly, a systematic investigation of our own human experience can never tell us whether a machine also has subjective experience, nor do we have any other form of directly accessing such a putative phenomenon. The distinction between e-Umwelt and p-Umwelt could here be used to di.erentiate the important work of investigating which parts of a systemÕs training data and input constitute the relevant feature space that determines its outputs (essentially an analysis of its e-Umwelt, if we bracket our ignorance of whether the system has any Umwelt in the full sense) from unwarranted speculations about the p-Umwelt such a system might have. 








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Appendix: English Translation of the ÒFoundational Rules of BiologyÓ 
This is my translation of the 21 Òfoundational rules of biologyÓ which UexkŸll posits at the end of Umwelt und Innenwelt der Tiere (2014[1921]: 236), di.erent selections of which are cited throughout the dissertation: 
Ò1. Every creature constitutes the center of its Umwelt, which it encounters as an autonomous subject. 
2. 
The Umwelt of any animal can be separated into a perception world and an e.ect world, which are united into a whole by the inner world of the body. 

3. 
In the Umwelt of each animal, there exist only things which belong exclusively to this animal. 

4. 
The things in the Umwelt of the animal appear to the external observer as uniÞed objects, while only unrelated features of the things enter the perception world on the one hand and the e.ect world on the other. 

5. 
The functional cycles of animals begin with the perceivable features of objects, extend through the inner world of the body, and reapproach the object with the e.ectors [of the animal]. 

6. 
Thereby the object becomes the carrier of perceptual features on the one hand and the carrier of actions for the animal on the other. 

7. 
The carriers of perceptual features and the carriers of actions always coincide in the same object. 

8. 
Perceptual features and e.ect-surfaces of the object are held together by the correspondence framework. 

9. 
The correspondence framework of the object is contained within the Bauplan of the subject, even though it never enters into a direct relation with the body of the subject. 

10. 
As soon as their activity starts, the functional cycles form a mechanism closed in on itself which includes the correspondence structure. 

11. 
The activity of every functional cycles ends with the exclusion of the carrier of a perceptual feature from the Umwelt. 

12. 
The Umwelt is only indexed fully when all functional cycles (of the medium, the prey, the enemy, and the sexes) have been circumscribed. 

13. 
Every Umwelt of an animal forms a part of the world of appearances of the observers which is delineated spatially, temporally, and with respect to its content. 

14. 
The observer can only perceive the features acting on the animal as traits of his own world of appearances. The sensations of the animal remain forever hidden to him. 

15. 
Every animal carries its Umwelt around with it for all its life like an impenetrable shell. 

16. 
The same is true of the observerÕs world of appearances, which closes him o. completely from the universe, since it constitutes his Umwelt. 

17. 
The space and time of the observer are located in his world of appearances. It contains the sky, which rings the horizon with sun, moon, and stars as his exclusive possessions, and moreover the ground with humans, animals, and plants, as far as his senses can reach. 

18. 
A universal, absolute space and a universal, absolute time, which encompass all living creatures, do not exist. 

19. 
The world of appearances of each human being likewise resembles a hard shell, which constantly encloses them from birth until death. 

20. 
The emergence and vanishing of these worlds is the last problem towards which science moves with unfailing certainty. 

21. 
Of the laws which create and destroy life, we can only say that an all-encompassing orderliness underlies them, which Þnds its clearest expression in the perfect Þtting of every animal into its Umwelt.Ó (UexkŸll 2014[1921]: 236-237) 




