Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences Breaking the self Radical disruptions of self-consciousness and impossible conscious experiences Wanja Wiesea (wawiese@uni-mainz.de) Abstract Are there logically possible types of conscious experience that are nomologically impossible, given independently justified assumptions about the neural underpinnings of consciousness in human beings? In one sense, this is trivial: just consider the fact that the types of perceptual experiences we can have are limited by our sensory organs. But there may be non-trivial types of conscious experience that are impossible. For instance, if there is a basic type of self-consciousness, corresponding to a phenomenal property that is nomologically necessary for consciousness, then experiences lacking this phenomenal property will be (nomologically) impossible. More generally, it may be that there are causal dependencies between the neural mechanisms that are required to instantiate distinct phenomenal properties (in human beings). If this is the case, instantiating one of these phenomenal properties without certain others may be impossible, which means there are non-trivial cases of nomologically impossible types of conscious experience. This paper clarifies this hypothesis, outlines a general methodology for its investigation, and relates it to research on radical disruptions of self-consciousness. Keywords Consciousness ∙ Impossible conscious experiences · Self-consciousness · Sense of agency · Sense of boundaries · Sense of time This article is part of a special issue on “Radical disruptions of self-consciousness”, edited by Thomas Metzinger and Raphaël Millière. 1 Introduction This paper explores the hypothesis that some logically possible configurations of self-consciousness are nomologically impossible, given certain assumptions about consciousness and its neural underpinnings in human beings. Put differently, an impossible conscious experience, as defined here, is an experience that cannot be aJohannes Gutenberg University Mainz Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://philosophymindscience.org https://orcid.org/0000-0003-3338-7398 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Wanja Wiese 2 generated by human brains.1 Radical disruptions of self-consciousness involving a total loss of self-consciousness are logically possible, but some authors doubt that they are nomologically possible (given the human neural architecture). If cor- rect, this would provide an example of an impossible conscious experience. How- ever, as some of the other contributions to this special issue show, that claim is at least controversial (and probably false, see Letheby, 2020; Metzinger, 2020; Mil- lière, 2020, all in this special issue; for the opposite view, see Sebastián, 2020, this special issue) – hence, I will not take a stance on the question whether conscious experiences without any kind of self-consciousness whatsoever are possible. Instead, I will pursue slightly more general goals. First, I will argue that research on impossible conscious experiences is relevant to understanding consciousness. If we had a complete theory of consciousness (including detailed knowledge of the neural mechanisms of consciousness), we would be able to say which types of conscious experience are possible and which are not. I shall argue that the reverse statement is also true: impossible experiences can provide insights into the neural mechanisms of consciousness. Secondly, I will propose a general methodology for finding evidence for impossible conscious experiences. In addition, I will argue that radical disruptions of self-consciousness (whether they involve a total loss of self-consciousness or not) provide particularly good opportunities for finding candidates for impossible experiences. In what follows, I will first define what an impossible conscious experience is (section 2), and why research on impossible conscious experiences is relevant (sec- tion 3). Then I will propose general strategies to investigate impossible conscious experiences (section 4). Finally, I will apply one of these strategies to an exam- ple, viz. the hypothesis that having a sense of agency without a sense of time is impossible (section 5). 2 What exactly is an impossible conscious experi- ence? The brain is an extremely plastic organ that is capable of generating a seemingly unbounded number of different conscious experiences.2 At the same time, the brain is a finite organ, which has not been selected for its ability to generate the largest number of logically possible experiences, but for its ability to enable flexi- ble control of behavior in changing environments. Therefore, it is likely that some types of conscious experience are logically possible, but in fact impossible for crea- tures like us. This is the main hypothesis of this paper: There are logically possible 1Unless indicated otherwise, I will use “possible” and “impossible” to refer to nomological possibil- ity throughout this paper. 2I will use the terms “conscious experience”, “experience”, and “conscious state” interchangeably in this paper. Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Breaking the self 3 types of conscious experience that are nomologically impossible,3 given indepen- dently justified assumptions about the neural underpinnings of consciousness in human beings.4 In the following, I shall use the term “impossible (conscious) ex- perience” as a shorthand for this more complicated formulation (unless indicated otherwise). This formulation raises a few questions: 1) How do we individuate types of conscious experience? 2) What are independently justified assumptions about consciousness and its neural underpinnings? 3) What does it mean to say that a conscious experience is nomologically impossible, given certain assumptions? The first question asks for individuation criteria for types of conscious experience. The second question asks about the relationship between types of experience and types of neural activity and structure. The third asks what bearing this relation- ship has on whether a given type of experience is nomologically possible or not. Let us address these questions in turn. 2.1 Individuation criteria Here, I will stipulate that types of conscious experience can be individuated in terms of their phenomenal character, i.e., by the phenomenal properties instanti- ated by these experiences. Examples of phenomenal properties are experienced perceptual features, such as experienced redness, the experienced smell of a rose, a feeling of warmth in your body, the sense of mental ownership accompanying 3This is trivially true, in the sense that we cannot have experiences that would, say, require radically different sensory organs. I distinguish this from a different, substantial sense of impossibility in section 3.1 below. 4One could try to subsume this under a notion of “biological impossibility”, derived from Tim Bayne’s concept of biological necessity: Many features of human beings are not necessitated by our design specifications but vary from one biologically normal human being to another. […] But other fea- tures of our nature – such as the possession of a heart – are mandated by our design specifications; they are included within our functional blueprint. […] [A] feature can be ‘biologically necessary’ without being an essential feature of all possible human beings. (Bayne, 2014, pp. 526–527) Biologically necessary features are features that all “biologically normal” human beings possess. As Bayne emphasizes, such features need not be essential features of all possible human beings, because one could change a person’s “normal” features by intervening with their body. After the intervention, the person may continue to be a human being, without being “biologically normal”. Instead of using the notion of biological normality to define biological necessity, one could use it to refer to features that no “biologically normal” human being possesses, and call these features “biologically impossible”. However, this raises the question: What counts as normal and what does not? Answers to this question will, to a large extent, be a matter of debate, and there are likely to be many borderline cases. Furthermore, restricting the notion biologically normal to “normal human brains” raises similar questions. For this reason, I am using the more complicated formulation “nomologically impossible, given independently justified assumptions about consciousness and its neural underpinnings in human beings”. I unpack this formulation in the main text. Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Wanja Wiese 4 many conscious thoughts, or a feeling of effort while thinking about a puzzling philosophical problem. I will, furthermore, assume that phenomenal character is grounded in (phe- nomenally represented) intentional content. In particular, I assume that conscious experiences have accuracy conditions, and that they determine what it is like to have those experiences. The intentional content of a conscious experience is then a phenomenal content. Some philosophers distinguish between phenomenal con- tent and the phenomenal mode of presentation:5 the idea would be that the dif- ference between, say, consciously seeing a fluffy puppy and consciously touch- ing its fur is not exhausted by a difference in phenomenal content; as a result, such authors would distinguish between two types of phenomenal properties (see Chudnoff, 2013, pp. 565–566), or would argue that phenomenal properties are not determined by pure representational properties (i.e., one would also have to spec- ify the particular phenomenal manner in which something is represented, such as a visual or auditory phenomenal manner – see Chalmers, 2004, pp. 159–161, for discussion). Here, I shall assume that there are no differences in phenomenal character that cannot be accounted for in terms of differences between represen- tational content, and that one does not have to distinguish between two types of phenomenal properties: there are only phenomenal properties corresponding to phenomenal contents, and differences in the phenomenal mode or manner of rep- resentation can be analyzed as differences in contents – but note that the claims argued for later in this paper do not depend on these background assumptions. Must two (token) experiences of the same type have the same phenomenal character? Or does similarity of phenomenal character suffice for membership of a given type of conscious experience (Koksvik, 2014, p. 129)? Relatedly, how de- terminate do the phenomenal properties picked out by a description of a type of experience have to be (Kriegel, 2015, p. 10)? For the purposes of this paper, nothing hinges on how we answer these questions. After all, we want to find descriptions of conscious experiences that cannot be created by the human brain. The (token) conscious experiences falling under a given description may have the same or only similar phenomenal characters (for instance, because they instantiate different de- terminates of the same determinable phenomenal property) – and there may be reasons to regard them as tokens of the same or of different types of experience. But what counts is what they have in common: they are nomologically impossible (independently of whether they share membership of the same type of experience or not). 5Just as one can distinguish between intentional content and intentional mode (see Crane, 2009, p. 477; Searle, 1983, p. 6), or between representative content and psychological mode (see Searle, 1979, p. 82). Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Breaking the self 5 2.2 Consciousness and the brain We cannot find impossible conscious experience (in the way in which black swans can be found), so we can at most hypothesize that a given description of a con- scious experience does not refer to any nomologically possible conscious experi- ences. How can this hypothesis be tested? I shall suggest that we find evidence for a possible explanation as to why the type of conscious experience in question is impossible. Such an explanation must make some assumptions about the neural underpinnings of consciousness, because it purports to explain why the brain can- not generate this type of conscious experience. Furthermore, these assumptions should ideally either be statements for which strong empirical support already ex- ists, or they should enable us to derive empirical hypotheses that can be tested in practice (not just in principle). In addition to this, there may also be useful as- sumptions that are to some extent theoretically justified (for instance, assumptions about general computational principles implemented by neural activity). These should at least be consistent with currently available empirical evidence. I shall say more about such assumptions below, in section 4.2. 2.3 Nomological possibility and the brain Why do we have to make further assumptions about the brain to justify the claim that a given type of experience is nomologically impossible? After all, don’t the laws of nature already put constraints on possible conscious experiences? This is certainly true, and there may be many interesting types of conscious experience that are nomologically impossible, but logically possible, regardless of how con- sciousness is generated in the human brain. However, as intimated in the previous paragraph, “finding” impossible experiences is methodologically difficult. Adding constraints that are more specific than constraints derived from physics alone can therefore facilitate finding candidates for impossible experiences. To the extent that these additional constraints suggest empirically testable hypotheses, we do not have to rely on theoretical considerations alone to justify the claim that a given type of experience is impossible. A description of an impossible conscious experience, in the sense used in this paper, must therefore specify a phenomenal character (i.e., a phenomenal prop- erty) and suggest why the human brain is incapable of generating an experience with this phenomenal character. But why should some types of experience be impossible in the first place? Here is a prima facie reason why we should expect that there are systematic limits on the types of conscious experience that the brain is capable of creating. The ability to generate consciousness is likely to serve an adaptive function, and this includes the ability to regulate consciousness or to shut it down. Extreme pain can cause subjects to faint, and this may have an adaptive value. Crucially, it also suggests that there is a threshold above which no pain experience is possible (because consciousness will be shut down if this threshold is crossed). Assuming Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Wanja Wiese 6 that the intensity of logically possible pain experiences is unbounded (i.e., for every logically possible pain experience, there is another that is even more painful), this suggests that certain phenomenal properties (“more than extreme” painfulness) cannot be instantiated by the human brain. More generally, there may be other “extreme” phenomenal properties, or combinations of phenomenal properties, that cannot be instantiated by the human brain, because of the way in which the brain generates and regulates conscious experience. To clarify and test these ideas, we need a more systematic way of arriving at descriptions of impossible conscious experiences; this will also allow us to specify how such experiences are still logically possible. In the following section, I will motivate and describe three different strategies. 3 Why are impossible conscious experiences rele- vant for consciousness research? Any scientific theory needs a clear description of its target domain. Phenome- nal consciousness is particulary vexing in this respect, because defining the ex- planandum is notoriously difficult. Although it seems we can, conceptually, dis- tinguish phenomenal consciousness from mere tonic alertness (Metzinger, 2020), attention, the capacity for integrated control of behavior, and other cognitive ca- pacities (see Chalmers, 1995; Revonsuo, 1998), we cannot completely dissociate phenomenal consciousness from these phenomena, and their relationship remains debated. This points to a central feature of theory-building in consciousness re- search, viz. that more rigorous specifications of the target phenomenon (i.e., phe- nomenal consciousness) have to rely on empirical results. As research progresses, we gain deeper insights into the relationship between phenomenal consciousness and cognitive capacities. For instance, we learn more about which perceptual and cognitive tasks can be performed unconsciously (Lamme, 2015) and which require consciousness.6 Discovering phenomena that do not (necessarily) involve conscious processing enables one to circumscribe the concept of consciousness. In addition to this, it is also possible to constrain the concept of consciousness from within, by consider- ing tasks that cannot even be performed consciously. For instance, although some savants are able to perform highly remarkable forms of mental arithmetic, there are limits to what is humanly possible. Some people are able to consciously ex- 6One could object that such empirical discoveries do not tell us anything about the concept of consciousness, but merely contingent facts about how consciousness and cognitive capacities are related in actual human beings. In other words, it is conceivable that there are beings with the same cognitive capacities, but without consciousness, or beings with conscious experiences that are impossible for us. First, this objection seems to presuppose a strong separation between em- pirical investigations and conceptual analyses. Secondly, even if our current, folk-psychological concept of consciousness is extremely general, it can be useful to develop a more specific, scientific concept of consciousness, which will mainly apply to actual human beings. Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Breaking the self 7 perience the process of multiplying astronomically large numbers, but no human being is able to mentally multiply two arbitrary numbers with one million digits each. Speaking more generally, there are limits on cognitive capacities (e.g., on the capacity of working memory7), and therefore also limits on consciousness, be- cause one cannot8 experience the exercise of a cognitive capacity if one does not possess this capacity in the first place.9 Call this the ability approach to impossible conscious experiences. A further approach is to consider phenomenal properties that vary on a con- tinuum. A possible example is the experience of toothache, which varies from a dull feeling of pressure to a sharp pain of tremendous intensity. Other possi- ble examples include the experienced brightness of a visual stimulus, the experi- enced loudness of a sound, or the experienced sweetness of a piece of food.10 The core assumption underlying this approach is that there are levels of intensity that cannot be consciously experienced by human beings. Call this the intensity ap- proach.11 As a simple example (which is not related to consciousness), consider a flexible stick. The stick can be bent to some extent, but (as we shall assume) it will eventually break, if the bend becomes too extreme. Bending the stick beyond the point at which, as a matter of fact, it breaks is logically possible, but nomolog- ically impossible (given the physical nature of the stick). Similarly, instantiating extreme phenomenal properties may be logically possible, but nomologically im- possible (given the nature of our brains). This might also apply to some forms of self-consciousness: finding out at which point “the self breaks” can provide hints about the underlying neural mechanisms. In this paper, I will pursue a third approach. The main assumption is that there are phenomenal properties that are dependent on each other, such that it is 7As is well-known, human working memory is limited to around 7 “items” (Miller, 1956). While the precise capacity of working memory may vary developmentally or be context-dependent (for a review, see Cowan, 2010), it is out of the question that the capacity of working memory is limited. For instance, states of consciousness that involve imagining a number of 30 specific chunks in working memory are nomologically impossible. 8Even if one imagined exercising a capacity one does not have, the experience could not be one of exercising that capacity, but would be a different experience. 9I am grateful to Martin Dresler for suggesting this. 10The claim that such properties vary on a continuum should be taken with a grain of salt. In particular, I do not want to claim that there are infinite different levels of intensity, nor that they can be measured in the way temperature can be measured. Following a suggestion by the editors of this special issue, it may even be more appropriate to say that what differently intense feelings of pain have in common is that they pertain to the same (natural) kind of phenomenal property, even though they are distinct phenomenal properties. The idea would then be that certain members of this kind of phenomenal property cannot be instantiated by human brains. 11Upon closer inspection, this approach may partly overlap with the ability approach. While the latter focuses on cognitive capacities, it may be possible to characterize the current approach in terms of perceptual abilities. For instance, the fact that there are limits on experienced loud- ness could also be formulated as the fact that the loudness of sounds cannot be discriminated beyond a certain threshold. This would presuppose that phenomenal differences go along with discriminatory abilities, which is not uncontested. Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Wanja Wiese 8 nomologically impossible to experience one without the other. The (hypothesized) reason for this is that there are causal dependencies between the neural underpin- nings of these phenomenal properties. Call this the dependency approach. Below, I will give the sense of time (i.e., experiencing the passage of time) and the sense of agency as a potential example: the hypothesis would be that the sense of time is causally necessary for the sense of agency, because of dependencies between the neural realizers of those phenomenal properties. More generally, self-consciousness provides a useful testbed for the depen- dency approach. Self-consciousness is not a unitary, simple phenomenon. Instead, it is characterized by a variety of features, such as de se thought, body ownership, spatial self-location (Millière, 2020, this issue, p. 5), a pre-reflective self/non-self dis- tinction, a sense of agency, patterns of affective states (Gallagher & Daly, 2018, p. 4), a sense of time, or a sense of center (Ataria, Dor-Ziderman, & Berkovich-Ohana, 2015, p. 142). None (or few) of these features are necessary for self-consciousness (in fact, it is even controversial whether all of them exist, and whether they are really distinct). Put differently, self-consciousness should be treated as a mon- grel concept (just as the more general concept “consciousness” – see Block, 1995). Similar versions of this view have been expressed as a pattern theory of self (Gal- lagher, 2013; Gallagher & Daly, 2018; Newen, 2018), or as the claim that “self- consciousness may be best construed as a multidimensional construct” (Millière, Carhart-Harris, Roseman, Trautwein, & Berkovich-Ohana, 2018, p. 1). What I take to be central to this position is that particular types of self-consciousness are best characterized in terms of a variety of features. Crucially, some of these features may be sufficient without being necessary for self-consciousness. This means that different types of self-consciousness can be instantiated (probably independently of each other). In addition, this enables the hypothesis that some combinations of features are nomologically impossible (although they are logically possible). Again, evidence regarding how “the self breaks” in radical disruptions of self-consciousness can suggest hypotheses about which combinations of phenomenal properties related to self-consciousness are possible and which are not. I will elaborate on this in section 5. In sum, investigating impossible conscious experience is valuable, because it increases our understanding of consciousness (by narrowing down the concept of consciousness). But in addition to that, explanations of why certain conscious experiences are impossible may yield insights into the neural mechanisms under- pinning consciousness. 3.1 Two types of impossible conscious experiences Before moving on, it will be important to make a distinction between two types of impossible conscious experiences. One of them is rather trivial.12 The other 12I am grateful to an anonymous reviewer for pressing me on this issue. Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Breaking the self 9 turns the claim that there are impossible conscious experiences into an interesting hypothesis. I will introduce this distinction by using an analogy. Imagine you are painting with a brush and a small set of watercolors. Pro- vided you have the three primary colors, cyan, yellow, and magenta, you can mix all other colors. If you only have cyan and magenta, you will only be able to mix a more restricted set of colors. For instance, painting in orange will be impossible for you, given your watercolor equipment. Still, painting in orange is logically pos- sible, and even nomologically possible, if we relax the constraints on watercolors that are at your disposal. Human consciousness is similarly constrained. We have a certain set of sensory organs, which shape the way we experience the world. There are types of experience we will never have, for the simple reason that we lack the required sensory organs and do not have the neural machinery that would control and make sense of signals received through them. With a nod to Thomas Nagel (1974), one could point out that we will never have a bat’s conscious expe- rience. But this type of limitation is trivial, because it does not reflect the way our brains create consciousness. In order to overcome this type of limitation, we would have to augment our senses (or the way we use them, cf. Teng & Whitney, 2011); this would enable us to have conscious experiences that were impossible beforehand (just as adding a primary color extends the set of possible colors you can paint with). We might even be able to have experiences that are similar to experiences of bats (even if this might not show us what being a bat is like for a bat). Now imagine you are painting on a dark, absorbent piece of wood. You have all three primary colors, but the consistencies of the colors differ: your yellow color is nice and pasty, but your magenta and cyan are too thin to leave a visible mark on the wooden board. The yellow color, by contrast, can readily be applied to the ground. Fortunately, you find out that you can still mix cyan and magenta with yellow, and the mixed color can be applied as nicely as the pure yellow color. This means you can paint in pure yellow, in green, orange, and any colors that are obtained by mixing all three primary colors. However, you will not be able to paint in pure cyan or pure magenta – because you will always have to mix those colors with a bit of yellow, in order to apply the color on your painting surface. In other words, some colors will be impossible for you, not because you lack the required primary colors, but because of how your painting equipment constrains the way in which you can paint. If consciousness is constrained in this way (and this is the hypothesis explored in this paper), then there will be dependencies between phenomenal properties (just as blue and red “depend on yellow” in the analogy). These dependencies are contingent on the neural mechanisms underlying consciousness in human brains. Although there is a sense in which the first type of impossible conscious experi- ences (e.g., perceptual experiences based on sonar signals) is also contingent on the neural mechanisms underlying consciousness, there is a crucial difference, be- cause the first type is not created by dependencies. Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Wanja Wiese 10 Let me further illustrate the second type of impossible experiences with a toy example: assume every human conscious experience is characterized by at most two phenomenal properties, and that these properties are binary (either the phe- nomenal property is instantiated or not; there are no differences in the degree to which the property is expressed). Every conscious experience can then be de- scribed as an ordered pair, in which each element is either zero or one (zero means the respective phenomenal property is present, and one means it is absent). The set of nomologically possible experiences, given our neural machinery (which can, by assumption, only instantiate two different phenomenal properties), is then a set of four conscious experiences (or three, if at least one phenomenal property must be instantiated). The set of logically possible experiences is much greater, because there are further phenomenal properties. Experiences that require instantiating further phenomenal properties are impossible experiences of the first type. Now assume that there is a dependency between the two phenomenal prop- erties (which is contingent on the way our brains create consciousness): the first phenomenal property cannot be instantiated without the second. If this is the case, then the space of nomologically possible experiences, given our neural machinery, has a hole: an experience in which the first phenomenal property is present, while the second is absent, is impossible. This is an impossible experience of the second type. This type of impossible experience is non-trivial. For, knowing that a sys- tem can have experiences with certain phenomenal properties, it is not obvious that some combinations of these phenomenal properties are impossible. 3.2 Constraining models of consciousness What can impossible experiences tell us about the neural mechanisms of conscious- ness? Note first that it is straightforward to see that the opposite is true: if we had a complete theory of consciousness (including detailed knowledge of the neural mechanisms of consciousness), we would be able to say which types of conscious experience are possible and which are not. But can impossible experiences, con- versely, yield insights into the mechanisms of consciousness? I will argue that they can. We can see this most clearly by considering a strong type of dependency be- tween phenomenal properties. If there is a phenomenal property that is nomolog- ically necessary for consciousness, then conscious experiences without this phe- nomenal property will be impossible in the sense that is relevant here. Further- more, this will suggest that all other phenomenal properties depend on this prop- erty (at least causally). Certain types of self-consciousness may provide controversial examples: if there is a basic sense of self that is constituted by a particular phenomenal property, viz. a self quale (or “ur quale”, as it is called in Perlis, 1997, p. 509) that is necessary for consciousness, then conscious experience without this self quale would be im- possible. If correct, this would suggest that there is a causal dependency between Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Breaking the self 11 the neural underpinnings of this basic type of self-consciousness and the under- pinnings of all other phenomenal properties. Hence, such a dependency between a single phenomenal property and all types of conscious experience is likely to reveal insights into the neural mechanisms of consciousness. A crucial step would be to find the neural correlate of the self quale, and then to relate it to candidates for total neural correlates of consciousness (that are involved whenever a person is conscious, but not when she is unconscious). However, as already noted, the example is controversial. What is more, proponents of the claim that consciousness necessarily involves a basic sense of self usually explicitly reject the claim that this corresponds to a self quale (contra Perlis, 1997). For instance, Zahavi & Kriegel (2016) point out that “for-me-ness is not a detachable self quale that one could introspect in isolation from any other content of consciousness” (Zahavi & Kriegel, 2016, p. 39). This suggests that your visual experience of a red tomato and my visual experience of a red tomato never have any (maximally determinate) phenomenal properties in common. They may share the determinable property of seeing a red tomato, but always instantiate more determinate phenomenal properties that do not overlap. Another way of interpreting this view is that there is a sense in which a basic sense of self is a (necessary) phenomenal property, but one that cannot be instan- tiated without instantiating at least one further phenomenal property. This would still be in line with Zahavi’s and Kriegel’s claim that one cannot introspect the self quale “in isolation from any other content of consciousness”. Furthermore, it illustrates another interesting potential result of investigating candidates for im- possible conscious experiences. It could turn out that what we described as two distinct phenomenal properties 𝐹 and 𝐺 are in fact constitutively dependent prop- erties: 𝐺 may actually be a composite phenomenal property constituted by 𝐹 and 𝐹 ′, i.e., 𝐺 ≡ 𝐹 &𝐹 ′. The fact that 𝐺 depends on 𝐹 would then be trivial (just as 𝐹 trivially depends on itself). In a recent article, Zahavi (2018) points out that the basic sense of self is not an “additional experiential object” (Zahavi, 2018, p. 5). However, in line with the interpretation that all phenomenal properties constitutively depend on a self quale, one could turn this statement on its head: all other contents of consciousness, such as a visually experienced red tomato, are not additional experiential objects, but always involve self-content. The general idea of constraining models of consciousness by research on im- possible experiences is as follows. Instead of starting with an assumption of how consciousness is generated, we start with an assumption about the impossibility of certain types of experience. The evidence for impossibility can be preliminary (and non-conclusive). But from the assumption that certain types of experience are impossible, one can derive constraints on their neural underpinnings. In the ideal case, this will allow one to derive testable predictions. If these predictions bear out, we gain further support for the hypothesis that certain types of conscious experience are impossible, and we learn (much) about the neural underpinnings of Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Wanja Wiese 12 those types of conscious experience. If the predictions do not bear out, we should lower our confidence in the impossibility hypothesis (and we may not learn as much about the neural underpinnings of conscious experience). 3.3 Matching descriptions at different levels of analysis There is another, more theoretical benefit that research on impossible conscious experiences may yield: it may increase our understanding of what phenomenal properties are in the first place, by providing support for structural theories of consciousness. If we want to understand consciousness, we have to understand the charac- teristic features of consciousness. Features of consciousness are usually described on a personal level of analysis (as opposed to subpersonal levels – for this distinc- tion, see Dennett, 1969; Drayson, 2012, 2014). The personal level of analysis has a variety of properties that make it difficult to establish links to subpersonal lev- els, on which functional, computational, or neurobiological features of conscious systems are described. For instance, phenomenological reports are subjective (as opposed to objective) and often make reference to phenomenal and intentional properties (as opposed to functional and physical properties). Still, one can learn a lot about consciousness without worrying about these most difficult aspects of consciousness: research on consciousness usually operates under the assumption of what David Chalmers (1995, 1996) calls “the principle of structural coherence”. He defines it as follows: This is a principle of coherence between the structure of consciousness and the structure of awareness. […] Briefly put, we can think of aware- ness as direct availability for global control. […] In general, any infor- mation that is consciously experienced will also be cognitively repre- sented. […] This principle reflects the central fact that even though cognitive processes do not conceptually entail facts about conscious experience, consciousness and cognition do not float free of one an- other but cohere in an intimate way. (Chalmers, 1995, pp. 212–213) The principle of structural coherence, if true, alleviates the problem of matching phenomenological descriptions of consciousness with descriptions at subpersonal levels of analysis. For instance, research on the neural correlates of consciousness can be conducted by finding systematic relationships between availability for ver- bal or non-verbal report and neural activity in different areas, and differences in reports (e.g., reporting a house vs. a face) can be matched with differences in neu- ral activity (e.g., in the parahippocampal place area vs. the fusiform face area, see Tong, Nakayama, Vaughan, & Kanwisher, 1998). But such research does not reveal why neural activity of a particular type is correlated with the presence of certain types of experience, and it does not by itself clarify “what it is like” (Farrell, 1950, p. 181; Nagel, 1974) to be in certain conscious states. Part of the answer may involve explaining why the experience Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Breaking the self 13 has the phenomenal character it has, and not a different phenomenal character. In particular, this leads to the question whether “inverting”13 phenomenal properties (an “inverted spectrum”) is possible: not knowing why a given neural activity goes along with the instantiation of a specific phenomenal property such as experienced redness, the connection between neural activity and phenomenal properties can seem more or less arbitrary, and it may seem as if one could permute a subject’s phenomenal properties without evoking any differences in behavioral or cognitive capacities. One way to block such inversion scenarios is to point to asymmetries in the space of conscious experiences (see Clark, 1996). For instance, if subjects are able to discriminate a larger variety of hues within a certain part of the color spectrum than in other parts, this could be taken as evidence that the space of conscious- ness (or “quality space” – see Rosenthal, 2015) is asymmetrical, and that inversion scenarios are impossible. Showing that certain types of conscious experience are impossible is another way of discovering asymmetries. If certain combinations of phenomenal proper- ties are impossible, the space of nomologically possible conscious experiences will have holes, which may involve asymmetries. For instance, an asymmetry exists if a phenomenal property 𝐹 can be instantiated without instantiating phenomenal property 𝐺, whereas 𝐺 cannot be instantiated without instantiating 𝐹 . Investi- gating impossible experiences may therefore contribute to developing structural theories of phenomenal properties (see also Wiese, 2018). 4 How can impossible conscious experiences be discovered? 4.1 The general idea Here, I will pursue what I called the dependency approach in section 3 above. This approach gives us at least two ways in which impossible conscious experiences can be discovered. A first starts with what we know about the neural mechanisms un- derpinning consciousness. To the extent that this enables us to see how contents of consciousness are determined by these mechanisms, it will also tell us about the limits to the contents that can be consciously experienced. A second approach 13In “inversion scenarios”, there are subjects with deviant phenomenal properties: for instance, whenever we would have an experience as of red, a subject with an inverted spectrum would have an experience as of green. If this inversion is systematic, it may not go along with any func- tional or behavioral differences, and it may be impossible to detect the presence of the inverted spectrum. Block & Fodor (1972) use such scenarios to argue that behavioral and functional crite- ria are insufficient to provide type-identity criteria for mental states – for if an inverted spectrum is possible, two subjects can have different types of conscious experience (because their phenom- enal properties differ), without any functional or behavioral differences. For an overview of the debate, see Byrne (2018). Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Wanja Wiese 14 starts from the other side: if a given type of conscious experience is impossible, what does this tell us about the neural mechanisms underpinnings consciousness? The dialectic is a bit more complex in this case: supposing that an experience 𝑒 is impossible, one tries to derive hypotheses about its neural underpinnings 𝑛. If these hypotheses about 𝑛 can be tested and are corroborated, this also supports the hypothesis that 𝑒 is impossible. The goal of the second approach is thus not just finding out about the limits of (contents of) consciousness, but finding phe- nomenological and, say, neurobiological constraints on consciousness at the same time. But why should we suppose that a particular conscious experience 𝑒 is impos- sible in the first place? Here, I am suggesting that we start with the observation that there is a lack of counter-examples: no report of an experience of a given type is known to exist. In other words, there is no evidence to the effect that the type of experience in question is possible. The crucial step in the argument is, of course, to move from a lack of counter-examples to positive evidence for the impossibility of a type of conscious experience. One can start with a model of how it could possibly be that a given type of ex- perience is impossible. This can then enable one to determine whether it is actually true (i.e., moving from a how-possibly to a how-actually model – see Machamer, Darden, & Craver, 2000, p. 21). In terms of explanation, this would involve starting with a possible epistemic explanation and using it to develop an ontic explanation (Craver, 2014, p. 37), e.g., by making hypotheses about the causal mechanisms involved, and then testing these hypotheses. How can this reveal that certain types of experience are impossible? On the one hand, it could turn out that the information processing involved in generat- ing a given type of experience is too complex to be realized by a human brain. This could be due to cognitive limitations or to physical constraints on the speed of information processing.14 On the other hand, and more fundamentally, there can be causal dependencies between the neural mechanisms that instantiate dif- ferent properties of experience. In this case, I shall also say that the properties are causally dependent (or that there is a causal dependency between the properties). As already noted, I will focus on this second approach in what follows. The challenge here is to find causal dependencies between properties. One could start by searching for correlations between properties. But a correlation between two properties 𝐹 and 𝐺 is compatible with different causal relations: 𝐹 may be causally necessary for 𝐺 (or vice versa), or there may be a third property 𝐻, the instantiation of which functions as a common cause, or there might be just a correlation, without any direct causal connection between 𝐹 and 𝐺. Hence, it will be useful (if not even necessary) to make further assumptions about features of consciousness and their neural underpinnings. Examples of such assumptions can be computational, functional, or neurobi- 14I am grateful to Philip Gerrans for suggesting thinking about constraints on the speed of process- ing. Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Breaking the self 15 ological. Since the exact neural underpinnings of consciousness are still unclear, it would be of little use to make specific assumptions about neural mechanisms underlying consciousness (unless they allow us to derive empirical hypotheses that can actually be tested using current neuroscientific methods). In general, the challenge here is to strike a balance between highly informative, but too specific, assumptions and non-informative, unspecific assumptions. The problem with too specific assumptions is that they are likely to be false (which, unfortunately, does not mean they can easily be falsified). However, if assumptions are too unspe- cific (but also more likely), they do not put any strong constraints on mechanisms underlying consciousness. Background assumptions must be specific enough to enable an explanation as to why a given type of conscious experience is impossi- ble, without making controversial claims that cannot be tested in practice. Here, I will suggest assuming, first, that computations implemented by the brain are relevant to understanding consciousness (note that this does not mean that implementing certain computations is sufficient for consciousness – see Schweizer, 2019), and, secondly, that these computations are (among others) characterized by the following two features: the ideomotor principle and the principle of spatio-temporal hierarchies.15 4.2 Two general computational principles as background as- sumptions According to the ideomotor principle, representations underpinning perception and action, respectively, overlap (at least partially). Some of the neural areas that are activated when I perceive someone move are therefore also activated when I con- duct this movement myself. This is the core idea of the ideomotor principle, which was first formulated by Johann Friedrich Herbart (Herbart, 1825, 1834), and was later picked up by William James (for a historical overview of ideomotor ideas, see Stock & Stock, 2004).16 Active inference provides a formal elaboration of this idea (and offers important extensions – see Wiese, 2017a; Friston et al., 2017a, 2017b). Note that merely adopting the ideomotor principle does not require rejecting other approaches to motor learning and control. For instance, the principle is com- patible with applications of optimal control theory to motor learning and control (see Herbort & Butz, 2012) – although researchers using optimal control theory do not typically incorporate the ideomotor principle in their models (cf. Wolpert, Ghahramani, & Flanagan, 2001; for critical discussion, see Friston, 2011). 15Incidentally, these are also key ideas of active inference, a framework developed by Karl Friston and colleagues (see Friston, Samothrakis, & Montague, 2012). However, the two computational principles can be accepted without presupposing that active inference provides an adequate way (let alone the only way) of modeling brain function. But I submit that the framework can still be useful to further develop ideas sketched in this paper. 16A further aspect of the principle is a particular view on how actions are learned – this will not be relevant to the discussion in this article. Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Wanja Wiese 16 Another feature that will be relevant here is the spatio-temporal hierarchy of information processing in the brain. The assumption behind this is that environ- mental features reflected in sensory signals vary with respect to their temporal and spatial grains. Some features are invariant over large spatial regions in objec- tive space (e.g., the color of the sky), and some are invariant over long temporal intervals in objective time (for instance, the size of my hands). An efficient way of representing mixtures of features of various temporal and spatial grains is by us- ing hierarchical representations. Lower processing levels represent features that change quickly and are more concrete. Higher processing levels represent features that are invariant over longer periods of time or larger regions of space (they may also be more abstract). This also resonates with the idea that percepts consists of hierarchical representations, in which the same objects are represented more than once (i.e., in different ways; cf. Lycan, 1996; Bayne & McClelland, 2018). So these are two computational features which, I will suggest, will be useful to find epistemic explanations as to why certain conscious experiences are impossible: the ideomotor principle and the principle of spatio-temporal hierarchies. Without getting into any formal details, we can already derive some constraints on how the brain represents the world. In particular, this also puts constraints on possible conscious experience, as we shall see now. Ideomotor principle. Action is partially underpinned by representations that are also activated when perceiving or imagining a similar action. This means, for instance, that there are limits on what can easily be imagined and observed at the same time. There must also be interferences between action observation and execution (for a review of empirical evidence, see Zwickel & Prinz, 2012; for a recent supporting study see Lohmann, Belardinelli, & Butz, 2019). Spatio-temporal hierarchy. If the contents of perception are hierarchical (which is suggested by hierarchical computational models), then temporal fea- tures are also represented at different timescales (Kiebel, Daunizeau, Friston, & Sporns, 2008). If such hierarchical models not only underpin unconscious percep- tion, but also determine the contents of conscious perception, then the experienced present is hierarchical as well (Wiese, 2017b). This has subtle implications for how to understand the conscious perception of temporally extended events, such as a melody: at short time-scales, we do not first experience one note, and then another note, together with an experience of “diachronic togetherness”. Rather, we expe- rience a single, temporally extended event (the melody or succession of notes) as a whole, and at the same time experience changing properties that belong to the same temporal whole. That is, we do not experience these different properties (e.g., notes) as belonging to different temporal parts of the whole event. Simon Prosser puts it thus: When we experience change we do not […] have experience as of an 𝐹 temporal part of an object succeeded by a non-𝐹 temporal part of that object, with it somehow understood that both parts belong to the same composite whole. (Prosser, 2016, p. 173) Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Breaking the self 17 This may sound puzzling, because it seems to require that we somehow experi- ence an object as having temporal parts and as not having temporal parts. But what Prosser emphasizes here is that we do not experience persisting objects as perduring, but as enduring. If they were experienced as perduring, they would be experienced as having temporal parts. Instead, we experience them as enduring, as being wholly present at any instant; and changing objects are, in addition, ex- perienced as having properties that are only transiently instantiated. Hierarchical models of temporal perception suggest a way to make this idea more precise: when two successive notes of a single melody are perceived, both are experienced as part of a single extended event, which is partly underpinned by a representation at a higher level (which represents properties at a more coarse- grained timescale).17 At that level, properties are represented as being instantiated now, but also as just having been instantiated – they are represented as continuing to be instantiated. This means that those properties cannot be represented as being instantiated now without thereby also being represented as being extended into the recent past and the near future (in other words, the objects having those properties are represented as enduring). Properties that are transiently instantiated (such as the pitch of a single note) are represented at lower levels, and can specify in what way enduring objects change. See figure 1 for an illustration. However, the point that is crucial for the purposes of this article is that higher levels encode objects that are temporally extended. I submit that these two computational principles, i.e., the ideomotor principle and the principle of spatio-temporal hierarchies, are general enough so as to func- tion as relatively uncontroversial background assumptions about neural mecha- nisms underlying consciousness. In other words, I only assume that neural activity underpinning consciousness is consistent with the way of representing the world entailed by these two features. At the same time, we have seen that these two features already constrain the way in which the brain represents the world. For this reason, they at least promise to suggest explanations of why certain conscious experiences may be impossible. In every particular case, we will need further, ad hoc assumptions, but general background assumptions, such as the ones specified here, will serve as guiding principles. Such assumptions and guiding principles specify at most epistemic explana- tions, in that they make it likely that certain conscious experiences are impos- sible. In other words, neither do they logically entail the impossibility of certain types of conscious experience, nor do they specify neural (causal) mechanisms that render certain experiences impossible. But they do specify mechanism sketches (cf. Machamer et al., 2000, p. 18; Piccinini & Craver, 2011), and thereby also sug- gest ontic explanations as to why a given candidate for an impossible experience cannot be created by human brains. An ontic explanation of a phenomenon de- scribes causal interactions between parts of a system, in a way that shows how the 17In Wiese (2017b) I call this a dynamic event representation (see Wiese, 2017b, p. 14). Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Wanja Wiese 18 Figure 1: The yellow bar illustrates a dynamic event representation. It is a distributed represen- tation of multiple properties (individual properties are represented by 𝑒1, … , 𝑒𝑛−1, 𝑒𝑛) that jointly specify a temporally extended event: near the top, properties that change slowly and are instanti- ated over a longer period of time (e.g., hundreds of milliseconds) are represented; near the bottom, properties that change quickly and are instantiated in the immediate present only (e.g., for less than one hundred milliseconds) are represented. The represented period of time during which the different properties are instantiated is illustrated with black arrows (marking the beginning and the end of each represented period during which a property is instantiated). Together, 𝑒1, … , 𝑒𝑛−1, 𝑒𝑛 represent a single, enduring event that we experience “as rising from the recent past, and as con- tinuing into the near future” (Wiese, 2017b, p. 13), because some of its properties remain invariant over a period of time that is slightly longer than the short interval we experience as the present. Together, they represent a specious present (James, 1890). (Figure adapted from Wiese, 2017b, p. 12.) activities of the parts and their organization give rise to the target phenomenon (see Craver & Tabery, 2017, sec. 2). The idea is thus that we can move from de- scriptions of computational features to descriptions of mechanisms, and this will (hopefully) enable us to derive testable predictions. 5 From radical disruptions of self-consciousness to impossible conscious experiences 5.1 General idea Recall that I suggest to start with the observation that no positive evidence for the existence of a given type of conscious experience exists. With respect to self- Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Breaking the self 19 consciousness, this means that there is a phenomenal configuration (a combina- tion of features associated with different types of self-consciousness), that is not reported in the literature (or in databases such as https://erowid.org). Given the many variations of phenomenal configurations reported in radical disruptions of self-consciousness, there is thus a prima facie reason to believe that the lack of evidence for the phenomenal configuration in question is not a mere coincidence. By itself, this reason is too weak to justify the claim that the phenomenal con- figuration at hand is indeed nomologically impossible. This is where the various approaches outlined in sections 3 and 4 come into play. As already pointed out, I will pursue the dependency approach, which focuses on causal dependencies be- tween the neural underpinnings of phenomenal properties. When two features are mutually causally dependent then one cannot be instantiated without the other. When only one feature depends on the other (𝐴 is causally necessary for 𝐵, but not vice versa), the first cannot be instantiated without the second, but the second can be instantiated without the first. Another type of causal dependency involves a third feature 𝐶, such that both 𝐴 and 𝐵 are causally dependent on 𝐶 (but 𝐶 need not be dependent on 𝐴 and 𝐵). In what follows, I will consider “the sense of boundaries” (Ataria, 2014), which is constituted by different phenomenal proper- ties. Two of them are the sense of agency and the sense of time, and I will suggest that the sense of time is necessary for the sense of agency. 5.2 The sense of boundaries We usually experience a boundary between ourselves and the world. I experience the world from a first-person perspective: I am at the center of my experience, I am on the inside, within the boundaries of my body, and the rest of the world is outside. Yochai Ataria (2014) calls this the sense of boundaries. The sense of boundaries corresponds to a bundle of phenomenal properties. It is particularly interesting because it is likely that the phenomenal properties constituting the sense of boundaries are not completely independent: at least some of them cannot be instantiated without also instantiating some other phenomenal properties. Put differently, there are configurations of phenomenal properties (associated with the sense of boundaries) that correspond to (nomologically) impossible experiences – or at least this is what existing research on the sense of boundaries suggests. But what exactly is the “sense of boundaries” (SB)? First of all, the SB is not identical to a physical boundary. Instead, it is an experienced boundary between one’s lived18 body and the rest of the world. Crucially, since the lived body depends on sensations in different sensory modalities, it can be modulated by changing sensory input (e.g., by closing one’s eyes or by entering a hot bath of water19), or by 18The lived body is a term used by phenomenologists to refer to the body, experienced as your own body, not experienced as an object. 19In some cases this can even affect the experienced boundary between the lived body and the environment. Millière (2019) cites a written interview, in which a deafblind individual describes Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Wanja Wiese 20 focusing attention on different aspects of one’s current experience (cf. Ataria, 2014). Moreover, Ataria (2014) distinguishes between the experience of boundaries and experiencing these boundaries as having determinate spatial locations (cf. Ataria, 2014, p. 1142; Martin, 1995, p. 271). Since boundaries between oneself and the world can be experienced in different ways, it is best to define the SB as a bundle of phenomenal properties. Ataria et al. (2015) characterize the SB in terms of several phenomenal properties (which they call “categories”), including the sense of agency and the sense of time (see Ataria et al., 2015, pp. 143–144). As already noted, I shall focus on these two phenomenal properties here. By the “sense of time”, one could mean different phenomena, for instance, the experience of temporal properties such as duration or succession, consciously remembering past events or imagining future events, a conscious estimate of how long it has taken to read up to this sentence, or having a sense of which of two temporally ex- tended events was longer.20 Ataria et al. (2015) do not give a definition of the sense of time. However, quoted reports in which their subject describes how their sense of time changes indicate that the sense of time is regarded as a gradual property and that it can also fail to be instantiated.21 The absence of the sense of time is described as “timelessness” in an earlier publication, to which the authors refer in a footnote (see Berkovich-Ohana, Dor- Ziderman, Glicksohn, & Goldstein, 2013). In a more recent publication, the sense of time is characterized as follows: Specifically, we are referring to a sense of a past continuing into the fu- ture; to the reduction in the sense of duration; and finally, to the sense of continuity itself which also disintegrates. (Dor-Ziderman, Ataria, Fulder, Goldstein, & Berkovich-Ohana, 2016, p. 3) I submit that the relevant notion of “sense of time” is that of the passage of time on short timescales. That is, it is not primarily about having a sense of the duration of past events, or of events on long timescales. Instead, it is about experiencing temporally extended events that are occurring now, have a duration, and reach into the very recent past and the immediate future (including internal events, such as the ongoing endeavor to regulate attention). Furthermore, the sense of time does not necessarily entail a sense of self, i.e., temporal experience without any form of self-experience may be possible (see Windt, 2015, pp. 18–19). the experience of a loss of spatial boundaries when they take a hot bath (see Millière, 2019, p. 271). 20I am grateful to an anonymous reviewer for asking me to be more specific about the sense of time. 21“Sense of time is obviously much clearer … yet I can’t describe it really” (Ataria et al., 2015, p. 139) “I would need to stop meditating, totally open my eyes and be in totally ordinary consciousness, only then would the sense of time come back fully” (Ataria et al., 2015, p. 140) “time is not relevant anymore” (Ataria et al., 2015, p. 142) Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Breaking the self 21 Furthermore, Ataria et al. (2015) suggest that there is a causal dependency between the sense of boundaries and the sense of time: It seems that the sense of time is a kind of ‘mirror reflection’ of the SB. Thus any alteration in the level of flexibility is reflected by a pro- portional adjustment in the sense of time. If we examine this phe- nomenon more broadly, we may say that the sense of self and the sense of time go hand in hand (Ataria et al., 2015, p. 143) Unpacking this statement requires a bit reflection, because the sense of time, as characterized by Ataria et al. (2015), is not an additional feature, but actually one of the features that constitute the SB. So saying that the SB changes whenever the sense of time changes would be trivial (just as saying that the state of my com- puter screen changes when one of the displayed pixels changes). However, the statement does suggest more substantive implications. First, it suggests that any change in the sense of time (i.e., its becoming weaker or stronger) is reflected in cor- responding changes in all other features constituting the SB. Secondly, it suggests that any change in one of the other features also goes along with a corresponding change in the sense of time. Perhaps the strongest interpretation would be that all of the features constituting the SB are positively correlated, such that the degree to which one of the features is expressed is predictive of how strongly (or weakly) the other features are expressed. For the purpose of illustration, let us consider the much weaker hypothesis that the sense of time is necessary for the sense of agency (which is one of the other properties constituting the SB). In a narrow sense, the sense of agency is the experience of causing a bodily or mental action (Gallagher, 2000, p. 15). In addition to that, there is a more general notion that includes the experienced ability to act (cf. Metzinger, 2013, p. 2). Let us call this the sense of ability (cf. Slaby, 2012). In what follows, “sense of agency” will refer to the general concept, which subsumes the sense of ability. I will also write “minimal sense of agency” for the sense of ability. Is it possible to have a sense of agency without a sense of time? If I experience myself as causing or generating an event that is occurring now, I must, by logical necessity, experience that causing as an event that is unfolding now. So a strong sense of agency (involving the experience of causing an action) seems to require a sense of time.22 This is compatible with the hypothesis that “timeless” experiences 22What if it is possible to experience an action that is not unfolding at any particular point in time, but is an “eternal” event? In fact, this might actually be the case in some drug-induced states in which the sense of time is thoroughly disrupted. Many such states may involve “thought loops” in which the same thought consistently recurs with no sense of when it begins and when it ends. A person may have the experience of causing a particular (mental) action, but without having the experience of causing it at any particular point in time, because the action does not have a determinate temporal location. Here, it would be relevant to determine whether an “eternal” event is best conceived as an event that has always existed and will always exist (in that case, it would have temporal properties) – or as an event that simply lacks any temporal properties (in Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Wanja Wiese 22 exist (in which there is no conscious experience of the passage of time at all). The idea is merely that a sense of time must be there whenever there is a sense of agency. What about the sense of ability? In its minimal form, the sense of agency only requires an awareness of possibilities for action. So the hypothesis derived from this example is that being aware of possibilities for action requires a sense of time. And this is equivalent to the hypothesis that a conscious experience involving a (minimal) sense of agency, but no sense of time, is impossible. If I merely experience the ability to initiate an action, I do not have to expe- rience the action as unfolding. Still, it seems that I have to experience this pos- sibility as referring to a future event, viz. a potential action that can be executed in the future. However, when I experience myself as having the ability to act, po- tential actions may be represented indeterminately,23 and they may not explicitly be experienced as future actions, but simply as something that can be done (or as something I can do) – just as I can think about potentially existing objects, without imagining that they exist at any particular point in time. But is it nomologically possible to experience myself as an agent, without experiencing the passage of time, given the background assumptions outlined in section 4 above? According to the ideomotor principle, there is an overlap between the repre- sentations involved in early action initiation (planning) and the representations involved in perceiving actual actions.24 Assuming that the phenomenal representa- tions contributing to the sense of ability include such “ideomotor” representations, we get a heuristic (epistemic) explanation of why one cannot experience oneself as being the potential author of actions, without having a sense of time. The explanation runs as follows. We are assuming that the sense of ability is underpinned by representations that can be used to initiate actions and to repre- sent actions that are actually unfolding. As such, they must be relatively high in the processing hierarchy. This hierarchy not only reflects differences in levels of abstraction, or differences in spatial grain, but also differences in temporal grain: at higher levels, features that change slowly are represented, which underpins ex- periences of endurance. Those features are relatively abstract and can be common to many different actions. This may explain why the sense of ability is not neces- sarily specific: I can experience the ability to act, without experiencing the ability to do anything in particular. But if I experience myself as the potential author of an action by experiencing myself as instantiating such an enduring feature, I thereby experience the passage of time, at least in a minimal sense, because the feature is experienced as being instantiated now, in the near future, and in the recent past. that case, a sense of agency without a sense of time would be possible. I am grateful to the guest editors of this special issue for suggesting this possibility. 23Such representations may also underpin existential feelings – see Ratcliffe (2012). 24As Bernhard Hommel, one of the proponents of the ideomotor principle puts it, the theory “is meant to provide a framework for understanding linkages between (late) perception and (early) action, or action planning.” (Hommel, Müsseler, Aschersleben, & Prinz, 2001, p. 849). Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Breaking the self 23 Put more simply, the idea is that the sense of ability inherits experienced temporal properties from representations of potential action. And since potential actions cannot be represented without reference to temporal properties (this follows from the two computational principles), the sense of ability must also involve a sense of time. This explanation is relatively ad hoc. In line with the dependency approach, empirical evidence must be sought for a causal dependence between the neural re- alizers of the representations referred to above. This would require making more specific hypotheses about the underlying mechanisms. Since the dependency be- tween the sense of agency and the sense of time mainly serves as an example here, further analyses remain a task for future work. But notice that the dependency approach may yield surprising results. So far, I have talked as if one could al- ways map phenomenal properties to distinct parts of a mechanism, and establish whether there is a causal dependency. However, it may also turn out that what has been described as a single phenomenal property (such as the sense of ability) actually involves different parts of a mechanism (which only sometimes interact and bring about a sense of ability). For instance, perhaps the sense of ability is underpinned by a structure that underpins the subject component and a structure that underpins the “object component” (potential action). The sense of time could be underpinned by a third structure, or it could be intertwined with the first two. Using background assumptions as a framework, some of these possibilities may be more likely than others. And in the end, the dependency between phenome- nal properties may even turn out to be more intimate than a causal dependency between different neural events. That is, it could turn out that there is actually a constitutive dependency between different phenomenal properties. Conclusion The general hypothesis of this paper is that some phenomenal configurations (com- binations of phenomenal properties) are logically possible but nomologically im- possible, given further assumptions about how the brain generates conscious ex- periences. I have argued that research on impossible conscious experiences may provide insights about neural mechanisms underpinning consciousness and is not just interesting for the sake of marking out the terrain of conscious experiences that can be generated by the human brain. I have described three approaches to finding impossible conscious experiences: the ability approach (which starts from limits on cognitive abilities), the intensity approach (which starts from considerations about extreme conscious experiences, involving phenomenal properties that vary on a spectrum, but may not exceed certain thresholds), and the dependency approach (which focuses on causal depen- dencies between the neural underpinnings of different phenomenal properties). Radical disruptions of self-consciousness provide a useful test bed for at least the dependency approach, since many types of self-consciousness can be Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Wanja Wiese 24 described in terms of combinations of phenomenal properties (such as the sense of agency or a sense of time). And if even in altered states (or radical disruptions) of self-consciousness certain configurations of phenomenal properties are not experienced, this warrants further explorations of the hypothesis that those configurations are indeed impossible. This does not presuppose that conscious experiences lacking any kind of consciousness of oneself are impossible. Rather, it assumes that there are different types of self-consciousness, and that at least some of them are dependent on other phenomenal properties. I have illustrated this with the hypothesis that the sense of agency requires a sense of time (without there being a logical implication between the two). In addition to investigating the neural underpinnings of actual conscious experiences, thinking about impossible conscious experiences may sharpen the conceptual tools used to describe conscious experiences and lead to deeper explorations of their underlying mechanisms. Acknowledgments I am grateful to two anonymous reviewers for constructive criticism and to Thomas Met- zinger and Raphaël Millière for their detailed comments on the penultimate draft of this paper. I would like to thank Jennifer Windt for comments on the accepted version of the manuscript, and the reviewers and participants of the Selfless Minds workshop at the Frankfurt Institute for Advanced Studies in 2018 for comments and constructive criticism. I thank Robin Wilson for editing the manuscript. References Ataria, Y. (2014). 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Psychological Research, 76, 171–182. https://doi.org/10.1007/s00426-011-0338-3 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 Interna- tional License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Wiese, W. (2020). Breaking the self: Radical disruptions of self-consciousness and impossible conscious experiences. Philosophy and the Mind Sciences, 1(I), 10. https://doi.org/10.33735/phimisci.2020.I.32 ©The author(s). https://philosophymindscience.org ISSN: 2699-0369 https://doi.org/10.3389/fpsyg.2018.00693 https://doi.org/10.1007/s13164-018-0403-6 https://doi.org/10.1007/s00426-011-0338-3 https://doi.org/10.33735/phimisci.2020.I.32 https://creativecommons.org/licenses/by/4.0/ https://philosophymindscience.org Introduction What exactly is an impossible conscious experience? Individuation criteria Consciousness and the brain Nomological possibility and the brain Why are impossible conscious experiences relevant for consciousness research? Two types of impossible conscious experiences Constraining models of consciousness Matching descriptions at different levels of analysis How can impossible conscious experiences be discovered? The general idea Two general computational principles as background assumptions From radical disruptions of self-consciousness to impossible conscious experiences General idea The sense of boundaries Conclusion