ARE THERE DEGREES OF SELF-CONSCIOUSNESS? Journal of Consciousness Studies, 26 (3-4), pp. 252-276 [Penultimate draft. Please cite the published version] Raphaël Millière (University of Oxford) Introduction Many philosophers, psychologists and neuroscientists appear to be sympathetic to the claim that the ordinary conscious experience of human beings involves a form of self-consciousness1. As such, this claim requires qualification. Thinking about oneself is a paradigmatic example of selfconsciousness; but it is dubious that human beings are normally thinking about themselves whenever they are conscious. In response to such concern, it is often emphasized that the kind of self-consciousness deemed ubiquitous in ordinary experience is minimal – more minimal than thinking about oneself. A number of authors have suggested that it is possible in principle to isolate "the simplest form of self-consciousness"2 or "the simplest form of self-experience"3 that accompanies most if not all conscious states. Moreover, some wonder whether "the most basic level of self-consciousness" is disrupted by psychopathologies such as schizophrenia4, or whether "infants do exhibit a rudimentary form of minimal self-awareness"5. These formulations may suggest that self-consciousness comes in degrees, and that individual subjects may differ with respect to the degree of self-consciousness they exhibit at a given time. In this article, I will critically examine this assumption. I will consider what the claim that self-consciousness comes in degrees may mean, raise some challenges against the different versions of the claim, and conclude that none of them is both coherent and particularly plausible. 1. Self-consciousness as a gradable property At a first pass, the claim that there are levels or degrees of self-consciousness means that creatures can be more or less conscious of themselves6. Specifically, it means that a creature may be more or less conscious of itself at one time than it is at a later time, and that it may be more or less conscious of itself than another creature at some time. Thus, the claim under consideration is that selfconsciousness is a gradable property of conscious creatures that can vary along a single dimension, both across time (for a particular creature) and across creatures7. Is this claim plausible? To start addressing this question, it is informative to consider a similar debate regarding consciousness in 1 See for example Zahavi (1999, 2005, 2014), Chalmers (1996, p. 10), Damasio (1999, p. 19), Metzinger (2003, p. 158), Kriegel (2009, p. 177), and Strawson (2011, p. 8). By "self-consciousness", I mean the subject's consciousness of herself (also called "self-awareness" or "sense of self"). Although I do not focus on this issue here, strictly speaking the relevant notion of self-consciousness refers to a consciousness of something as oneself, to exclude cases in which one is accidentally conscious of oneself (e.g. if I think about the lottery winner without realising that I myself am the lottery winner), and to remain neutral on the metaphysics of the self (i.e. whether there is actually a self which is the object of self-consciousness). 2 Blanke & Metzinger (2009, p. 12). 3 Windt (2015, p. 565). 4 Sass & Pienkos (2013, p. 117). 5 Hutto & Ilundáin-Agurruza (2018, p. 3). 6 In what follows, I will use "levels" and "degrees" interchangeably: if a creature A has a higher level of selfconsciousness than a creature B, then it is self-conscious to a higher degree, and vice versa. 7 Note that the notion of self-consciousness is occasionally used to refer to a dispositional property of conscious creatures, namely their capacity to be conscious of themselves. Accordingly, one could understand the idea that selfconsciousness comes in degree in terms of an ordering of dispositions for self-consciousness; one might argue, for example, that the members of a certain species of rodent are less self-conscious than human beings. However, the idea that self-consciousness is gradable as a dispositional property is often premised upon the assumption that the corresponding categorical property it itself gradable. For this reason, I will leave aside the dispositional use of selfconsciousness in what follows. 2 general. In the clinical literature on disorders of consciousness, the claim that creature consciousness – consciousness as a property of creatures – comes in degrees is often explicitly endorsed8. Patients in the minimally conscious state, for example, are said to be more conscious (or to have a higher level of consciousness) than patients in the vegetative state. The underlying assumption is that all global states of consciousness can be ranked in principle on a consciousness scale, ranging from the most minimal or basic level of consciousness to the highest level attainable by conscious creatures (see fig. 1). Fig. 1. Global states of consciousness ranked by level of consciousness However, the plausibility of this assumption has been challenged on the ground that the concept of consciousness does not typically refer to a graded property9. Indeed, a creature is commonly said to be conscious if and only if it has a subjective experience; but the property of having a subjective experience is not gradable – either one has such experience or one does not. A similar issue seems to arise with respect to self-consciousness. Presumably, either one is conscious of oneself or one is not, so it is not obvious that the property of being conscious of oneself is a gradable property. This point is not decisive, however, for it may be raised regarding other predicates that turn out to be gradable: for example, either one has money or one does not; yet if one does, one may have more money than someone else. Thus, something more needs to be said to rule out the hypothesis that self-consciousness (or consciousness in general) is a gradable property10. To address concerns about the intelligibility of a gradable notion of consciousness, it is sometimes suggested that levels of consciousness should be defined with reference to the degree to which mental contents are conscious, as opposed to global states of a creature11. While a creature can be in only one global state of consciousness at any given time, it may be in several specific conscious mental states at the same time – for example by having both a visual experience of an apple and a bodily experience of stomach pain simultaneously. If specific mental states can be more or less conscious, then a creature's level of consciousness could be equated with how conscious its most conscious mental state is. Similarly, one may attempt to make sense of the hypothesis that self-consciousness comes in degrees by focusing on specific mental states rather than global states of an organism. Let us call a conscious mental state M a state of self-consciousness if its subject is conscious of herself by virtue of being in M. As previously mentioned, conscious de se thoughts – conscious mental states of thinking about oneself – are paradigmatic examples of such states. The question is whether states of self-consciousness can be ranked along a single scale determining how self-conscious their subject is. One suggestion is that states of self-consciousness differ with respect to their vividness, and that such difference is the relevant metric to rank them on a "selfconsciousness scale". For example, a creature's level of self-consciousness at a given time could be equated with how vivid its most vivid state of self-consciousness is at that time. 8 See for example Laureys (2005), Giacino et al. (2002), Overgaard & Overgaard (2010), Boly et al. (2013) 9 Bayne et al. (2016). 10 To use a common metaphor, conscious experience is like the light of a lightbulb, which is either "on" or "off". But it may specifically be like a light with a dimmer switch: although it is either on or off, it also varies along a single graded dimension when it is on (see for example Kriegel, 2012, p. 482). The same analogy could be applied to selfconsciousness. While luminance is a gradable property that can easily be measured with a light meter, I will suggest that it remains unclear on what kind of scale degrees of self-consciousness could be mapped in principle. 11 Overgaard & Overgaard (2010). See Bayne et al. (2016) for a critical discussion of this proposal. 3 This proposal, according to which degrees of self-consciousness can be specified with reference to the vividness of specific conscious mental states, raises a number of issues. Even if we assume for the sake of argument that "vividness" is a gradable property of conscious mental states that can be reliably assessed and reported, it is debatable whether the degree of vividness of a creature's most vivid state of self-consciousness at a given time could be equated with the creature's alleged level of self-consciousness. Vividness is a generic property of all mental states that is unrelated to the self-representing nature of states of self-consciousness. The hypothesis that states of selfconsciousness can be ranked on a scale with respect to their putative vividness does not necessarily entail that their subjects can be more or less conscious of themselves. In response to these concerns, one might argue that the vividness of states of self-consciousness is not the right criterion to rank levels of self-consciousness adequately. Perhaps the right criterion should be some gradable property of mental states that is directly related to their self-representing content. For example, one could suggest that states of self-consciousness can be more or less "selfinvolving", and that a creature's overall level of self-consciousness is determined by the degree of self-involvement exemplified by its most self-involving conscious mental state at a given time. This strategy does not seem very promising, however, because the notion of self-involvement seems even vaguer than that of vividness. Presumably, a de se thought is "self-involving" in so far as it involves de se content, which is another way to say that its content includes the first-person concept and is suitably expressed by a statement using the first-person pronoun. It is unclear how a de se thought could be more self-involving than another, given that the property of involving the firstperson concept is not gradable12. So far, I have challenged the claim that the putative "vividness" or "self-involvement" of states of self-consciousness gives us a grasp on the proposal that self-consciousness is a gradable property of creatures. I suspect, however, that many proponents of a graded view of self-consciousness would contend that its plausibility crucially turns upon a distinction between several ways of being conscious of oneself. In what follows, I will explore this idea and critically examine the resulting account of levels of self-consciousness. 2. Modes of self-consciousness There seems to be an intuitive distinction between what one is conscious of and how one is conscious of it. Consider the difference between seeing an apple and seeing a pear; these two experiences differ with respect to their intentional object, namely what they represent. Consider now the difference between seeing, touching, imagining and thinking of a particular apple. These experiences share the same intentional object – they are all about an apple13. However, they do not share the same phenomenal character: what it is like to see a particular apple does not resemble what it is like to touch it or think of it. Some have argued that this phenomenal contrast is at least partly determined by the way in which the object is represented, which has been called "intentional mode" (Searle, 1983; Crane, 2003, 2009), "manner of representation" (Chalmers, 2004) and "attitude" (Kriegel, 2015). On this view, the experience of thinking about Barack Obama does not represent Barack Obama in the same way as the experience of seeing Obama, because thought and visual perception are two distinct intentional modes. My purpose here is not to engage in a general discussion of intentional modes14. Rather, I want to apply the distinction between different ways of being conscious of something to the case of consciousness of oneself. The idea is that states of self-consciousness may broadly speaking represent the same intentional object – the self – and yet differ with respect to the way in which 12 Alternatively, one could suggest that a creature's overall level of self-consciousness is determined by the number of self-involving conscious mental states the creature is in at a given time. I will come back to this proposal in the following sections, after introducing the idea that one can be self-conscious in different ways. 13 In this toy example, I am assuming that these experiences are all about the very same apple rather than some arbitrary apple. 14 For a defence of the claim that intentional modes are non-representational features of mental states, see Crane (2003, 2009) and Kriegel (2015). For a critical discussion, see Bourget (2017). 4 they represent it15. Accordingly, there are different ways in which one may be conscious of oneself, which I will now refer to as modes of self-consciousness. Many philosophers and psychologists endorse this pluralistic view of modes of self-consciousness, arguing that thinking about oneself is only one of such modes16. For the sake of clarity, I will refer to thinking about oneself as cognitive selfconsciousness. A number of authors claim that bodily awareness constitutes a non-cognitive mode of self-consciousness17. This claim is often motivated by arguing that our awareness of certain bodily sensations grounds first-person judgements that are immune to error through misidentification with respect to the first-person, where this immunity is heralded as a hallmark of selfconsciousness18. Some authors also argue that bodily awareness normally comes with a sense of body ownership by virtue of which we experience our body as our own19. I will refer to the mode of self-consciousness underlain by bodily awareness as bodily self-consciousness. Another candidate for a distinct mode of self-consciousness is the subject's conscious awareness of her spatial location with respect to her perceived environment20. Perceptual experiences, and visual experiences in particular, represent spatial properties of objects within an egocentric frame of reference21. This means that the location of environmental landmarks is represented with respect to a specific point of origin, which roughly coincides with the centre of the subject's head for human beings. Correlatively, the relative location of the point of origin of the visuospatial perspective is itself represented with respect to surrounding objects. Many authors have suggested that in normal perceptual experience, the location of the point of origin of the subject's visuospatial perspective is represented as the subject's location. Perceptual (visual) experience is self-locating, meaning that it represents the location of the self with respect to the perceived environment. In so far as self-locating perceptual content is associated with a specific phenomenology – a sense of being located with respect to one's environment – it may be said to constitute a form of selfconsciousness. This claim is further supported by the idea that self-locating perceptual content grounds self-locating judgements (such as "I am in front of this table") that are immune to error through misidentification with respect to the first-person22. I will refer to the mode of selfconsciousness underlain by the subject's awareness of her egocentric location as spatial selfconsciousness. I have introduced three ways of being self-conscious, or modes of self-consciousness: cognitive, bodily and spatial self-consciousness23. Can the distinction between different modes of self- 15 I remain neutral here on the metaphysics of the self. It might be the case that what is represented by states of selfconsciousness as oneself (a) exists and is adequately represented (i.e., self-representation is veridical), (b) exists and is systematically misrepresented (i.e., self-representation is illusory), or (c) does not exist (i.e., self-representation is hallucinatory). On this issue see McClelland (2017). 16 See for example Gallagher (2000, 2013), Bermúdez (2001), Zahavi (2014) and Peacocke (2014). 17 See Strawson (1966), Evans (1982), Sutton Morris (1982), Ayers (1991), Brewer (1995), Cassam (1995, 1997), Bermúdez (1998, 2011), Legrand (2006) and De Vignemont (forthcoming).. 18 For an example of this strategy see Bermúdez (2011). A judgement of the form "I am F" is said to be immune to error through misidentification with respect to the first-person if it is impossible that its utterer be right that something is F and wrong that she herself is F. The notion of immunity to error through misidentification was coined by Shoemaker (1968). For a critical discussion of whether bodily self-ascriptions are immune to error through misidentification, see De Vignemont (2011). 19 For an example of this strategy see De Vignemont (2007, 2013, forthcoming). For a critical perspective on the sense of body ownership, see Bermúdez (2011, 2015) and Alsmith (2015). 20 See Evans (1982), Cassam (1997, pp. 52–53), Hurley (1998), Bermúdez (1998; 2001; 2011), Peacocke (1998), Noë (2005) and Schwenkler (2014). 21 See Klatzky (1998) on the notion of egocentric frames of reference. 22 See Evans (1982), De Vignemont (2011) and Bermúdez (2011). 23 There are a few other candidates for distinct modes of self-consciousness, such as the sense of agency or the firstperson perspective, although they are arguably more contentious. The sense of agency refers to the experience of one's action as one's own (Haggard, 2017). However, the hypothesis that there is a sui generis phenomenology of agency is controversial (Grünbaum, 2015; Grünbaum & Christensen, 2017; Parrott, 2017), and the sense of agency is not easy to disentangle from bodily awareness. As for the "first-person perspective", it is an umbrella-term whose use often conflates several notions, including (a) the experienced location of the origin of the egocentric frame of reference structuring the visual field (equivalent to self-location), (b) the experience of one's absolute orientation in space with 5 consciousness shed any light on the idea that self-consciousness comes in degrees? One option would be to attempt ranking modes of self-consciousness in a definite order, from "lower" to "higher" forms of self-consciousness. I see two issues with this proposal. First, there is no obvious property of modes of self-consciousness that could serve as the criterion for such ranking. Admittedly, there is a difference between thinking about oneself on the one hand, and experiencing one's body or egocentric location on the other. Indeed, while de se thoughts engage the first-person concept (the concept of self), a number of authors have argued that the two other forms of selfconsciousness do not. Most conscious animals and infants, for example, presumably feel their body and location in egocentric space without possessing a concept of self. Consequently, it has been suggested that these forms of self-consciousness are rooted in nonconceptual de se content, rather than in the involvement of a full-blown concept of self24. This proposal does support the idea that modes of self-consciousness come in two flavours: they can be conceptual or nonconceptual. But it does not yield a ranking between bodily and spatial self-consciousness, nor does it warrant the claim that there is a "simplest form of self-consciousness"25 – since bodily and spatial modes of self-consciousness are both nonconceptual. There is a deeper issue with the suggestion that ranking modes of self-consciousness on a particular scale will make sense of the claim that creatures' or subjects' self-consciousness comes in degrees. Indeed, if there are distinct modes of self-consciousness, we can assume that any particular state of self-consciousness belongs to one of such modes. For example, a de se thought is an instance of cognitive self-consciousness, a proprioceptive sensation an instance of bodily selfconsciousness, and a self-locating visual experience an instance of spatial self-consciousness. But if this is the case, creatures are often in more than one state of self-consciousness at a given time. A subject can simultaneously have a visual experience of a table whose content represents her as being in front of a table, a proprioceptive experience whose content represents her legs as crossed, and think at the same time "my legs are crossed". In this situation, which does not seem particularly far-fetched, the subject is simultaneously conscious of herself in three different ways – cognitive, bodily and spatial. However, the fact that one can be in several modes of self-consciousness at any one time allows for an intriguing idea that appears to have some support in the literature: the hypothesis that modes of self-consciousness are systematically related in such a way that one can trace one-way dependence relations between them. I will now examine how this idea can be developed to justify the claim that self-consciousness comes in degrees, before arguing that it is challenged by empirical evidence. 3. The scaffolding model of self-consciousness The proposal that modes of self-consciousness are systematically related builds upon the broad idea that self-consciousness is a multi-layered phenomenon, which frequently involves more than one mode of self-consciousness at any given time. The crucial claim is that some modes of selfconsciousness are more fundamental or basic than others, and that more sophisticated modes can only occur concurrently with more basic modes. Specifically, a subject cannot be self-conscious in some way A unless she is also self-conscious in a more basic way B at the same time, unless A is the most basic mode of self-consciousness. On this view, self-consciousness is akin to a scaffolding: each floor or layer requires the floor below in order to stand, unless it is the first and lowest layer respect to gravitational cues (where is "up" and "down") and (c) what Alsmith (2017) calls "limitation structure", namely the fact that in (visual) perceptual experience things can only be perceived within a certain bounded region in space and may be occluded. See Millière (2017) for a disambiguation of the notion of first-person perspective as it is used in the scientific literature on full-body illusions and autoscopic phenomena. In this article I will leave aside the sense of agency. 24 For a discussion of the relationship between nonconceptual de se content and self-consciousness see Bermúdez (2011) and Peacocke (2014, 2015). The hypothesis that perceptual and bodily experience might carry nonconceptual content has generated a lot of debate, which I cannot go into here. 25 Blanke & Metzinger (2009, p. 12). 6 of the structure. Drawing on this analogy, I will refer to this view as the scaffolding model of selfconsciousness (Fig. 2). Bermúdez evokes a similar idea when he writes that "there are many distinct layers of selfconsciousness", each of which is "parasitic on a more primitive and already-existing form of selfconsciousness" with the exception of the bottom layer. Indeed, "it seems plausible that all these layers must eventually be grounded in a form of self-awareness primitive enough not to depend on a more basic self-awareness"26. There is, however, an important caveat to consider: Bermúdez appears to claim that one-way dependence relations hold between capacities for different modes of self-consciousness, and are determined by the order in which these capacities appear during the development of an organism. This ontogenetic claim does not necessarily entail that one organism may be more or less self-conscious than another at a given time. To draw upon the analogy with consciousness, the hypothesis that capacities for various intentional modes may unfold in a particular order during development (e.g. the ability to entertain thoughts emerges after the ability to have visual experiences) does not entail that consciousness comes in degrees, nor does it entail that one cannot exercise a capacity acquired at a later developmental stage without exercising at the same time all the capacities acquired at earlier stages. The same line of reasoning applies to a phylogenetic perspective on modes of self-consciousness; while interesting in its own right, the claim that the capacities for modes of self-consciousness appear in a particular order in the evolution of a species does not support the idea that self-consciousness comes in degrees for individual members of the species at any given time. By contrast, the scaffolding model of selfconsciousness holds that modes of self-consciousness are parasitic on each other in actual global states of consciousness, such that any mode of self-consciousness must co-occur with more basic modes of self-consciousness in the overall experience of a subject at any given time, with the exception of the most basic mode of self-consciousness27. The scaffolding model often rests upon the assumption that there is a single mode of selfconsciousness that a subject can be in without being in any other mode of self-consciousness, and that must also occur when all other modes of self-consciousness occur28. This assumption seems to show through in a number of publications in philosophy and psychology. For example, Blanke and Metzinger defined "minimal phenomenal selfhood" as "the simplest form of selfconsciousness" in an influential paper29. On their view, the simplest form of self-consciousness has to be both minimally sufficient and necessary for a creature to be self-conscious at all at any given time. There are two main candidates for the simplest form of self-consciousness in the literature, namely bodily self-consciousness and spatial self-consciousness30. If bodily self-consciousness is 26 Bermúdez (1995, p. 153). 27 Strictly speaking, the scaffolding model does not allow for a linear or total ordering of creatures according to the degree to which they are self-conscious at a given time, because on this view two distinct creatures may be equally selfconscious. 28 One could conceive of a scaffolding model in which there no single simplest mode of self-consciousness, but several modes of self-consciousness which are jointly necessary for all other modes to occur. For example, one could claim that bodily and spatial self-consciousness always co-occur with one another, and are necessary for cognitive selfconsciousness to occur at a given time. The empirical evidence discussed in the next section also challenges this version of the scaffolding model. 29 Blanke & Metzinger (2009, p. 12). 30 Here are few passages supporting one or the other of these options: "Bodily self-awareness seems to be one of the most tempting and attractive candidates for the basic level of self-awareness that might be at the core of a comprehensive account of the manifold forms of self-consciousness." (Gallese & Sinigaglia, 2011, p. 118); "Selfawareness at its most basic level is a presence to oneself as a conscious, bodily orientation towards the world" (Wider, 2006, p. 82); "[P]ure spatiotemporal self-location suffices for a robust sense of self" (Metzinger, 2013, p. 12); "Spatiotemporal self-location is sufficient for the simplest form of self-experience" (Windt, 2015, p. 565). In their original paper, Blanke and Metzinger (2009) suggested that body ownership and self-locating content jointly constitute the simplest form of self-consciousness. Metzinger has since revised his position, rallying to the weaker claim that selflocating content underlies the simplest form of self-consciousness (Metzinger, 2013). Note that Windt and Metzinger talk of spatiotemporal self-location rather than merely spatial self-location. In this context, temporal self-location refers to the sense of duration (Windt, 2014). This association seems premised upon the assumption that spatial self-location 7 the simplest form of self-consciousness in the relevant sense, then being conscious of one's body as one's own must be both sufficient and necessary to be conscious of oneself. This entails that any subject who is conscious of herself in some way (e.g. through de se thoughts or self-locating content) must also be conscious of her body. Similarly, if spatial self-consciousness is the simplest form of self-consciousness, then being conscious of one's location in egocentric space must be sufficient and necessary to be conscious of oneself. This entails that any subject who is conscious of herself in some way (e.g. through de se thoughts or bodily awareness) must also be conscious of her egocentric location (Fig. 2). In the next section, I will challenge both of these positions by discussing counter-examples to their empirical predictions. I will suggest that spatial selfconsciousness can occur without bodily self-consciousness, that bodily self-consciousness can occur without spatial self-consciousness, and that cognitive self-consciousness can occur without either bodily or spatial self-consciousness. Fig. 2. The scaffolding model of self-consciousness 4. Dissociations between modes of self-consciousness 4.1 Spatial self-consciousness without bodily self-consciousness There is converging evidence that it is possible for a subject to be aware of her spatial location within an egocentric frame of reference without being aware of her body, casting doubt on the hypothesis that bodily awareness is necessary for self-consciousness. Some might argue that this even occurs in rather mundane situations when one does not pay any attention to bodily signals, for example when one is mind-wandering or absorbed in a task or stimulus. Consider the experience of being enthralled by a captivating novel. This involves a visual experience of the book which presumably has self-locating content: it represents the book as being in front of me, and conversely represents me as being at a certain distance from the book. Assuming that the reader stands still, it is less obvious that her overall experience would necessarily include tactile, proprioceptive or interoceptive sensations. The assumption that bodily sensations are constantly present in the background of conscious experience might simply be an instance of the refrigerator light fallacy: bodily signals are experienced as soon as one focuses on them, but this does not warrant the conclusion that they are ubiquitous in all conscious experience31. In any case, there are altered states of consciousness that clearly involve self-locating content without bodily awareness. In a subset of out-of-body experiences (OBEs) known as "asomatic", subjects have the experience of being disembodied, without having the illusion of seeing their own is always accompanied by a sense of duration, although the opposite might not be true (Windt, 2014; Windt, Nielsen, & Thompson, 2016). I have suggested elsewhere that some global states of consciousness may lack any sense of duration (Millière, Carhart-Harris, Roseman, Trautwein, & Berkovich-Ohana, 2018), and I believe this also holds true of some global states involving spatial self-locating content. There are also independent reasons to argue that having sense of duration is not sufficient for being self-conscious (Windt, 2014). For these reasons, I will focus here on spatial self-location rather than "spatiotemporal" self-location. 31 See Schwitzgebel (2007) for an interesting discussion of this point. 8 body from the outside32. In fact, a recent study with a large sample size of both healthy participants and vestibular disorder patients who reported OBEs suggests that only 10% to 30% of such experiences feature the hallucination of one's "own" body in extracorporeal space33. As experiences of disembodiment, asomatic OBEs presumably do not involve bodily awareness. Interestingly, reports of asomatic OBEs sometimes mention the experience of being an extensionless point in space, which coincides with the origin of one's visuospatial perspective. These experiences do involve visual scenes with spatial properties, and there is no reason to believe that the subjects lack spatial self-consciousness. In the general population, there is also evidence that a small subset of dreams are "bodiless", meaning that the dreamers do not experience themselves as embodied within the dream34. In bodiless dreams, some subjects report that they "experienced themselves as a disembodied point or freely moving center of awareness"35. There is also converging evidence that certain drug-induced states may involve a complete loss of bodily awareness36. Early studies with mescaline and LSD already reported depersonalizationlike effects which occasionally involved a loss of bodily awareness37. On the psychometrically validated 5D-OAV questionnaire38 commonly used to assess the subjective experience of altered states of consciousness, healthy participants score high on the "disembodiment" factor, which includes the item "it seemed to me as if I did not have a body anymore", after administration of ketamine39, psilocybin40 and LSD41 compared to placebo. There is also anecdotal evidence from narrative reports that psychedelics can radically disrupt bodily awareness: "There was purely my sensory perception of my environment... I felt disconnected from my physical being, my body"42. In a recent neuroimaging study of DMT, a drug whose short lasting subjective effects are more intense and immersive than those of psilocybin or LSD, almost all participants reported a loss of awareness of their body for several minutes during the peak of the experience in post-hoc microphenomenological interviews43. This transitory experience appears to be lacking not only tactile and proprioceptive sensations, but also awareness of interoceptive signals, such as cardiorespiratory and visceral signals44. Interestingly, DMT induces complex and vivid hallucinations of three-dimensional visual scenes that appear to have self-locating content. For example, subjects were able to report about their position with respect to environmental landmarks in the hallucinatory scene. Thus, drug-induced states offer additional evidence that spatial selfconsciousness can occur without bodily self-consciousness. Taken together, these findings strongly suggest that bodily awareness is not necessary for selfconsciousness, and that bodily self-consciousness is not a suitable candidate for the simplest form of self-consciousness. I will now turn to the question of whether subjects can have bodily selfconsciousness when they lack spatial self-consciousness. 4.2 Bodily self-consciousness without spatial self-consciousness Although it is more difficult to find evidence for bodily self-consciousness without spatial selfconsciousness than for the opposite dissociation, at least three cases seem to exemplify this 32 Alvarado (2000). See Metzinger (2013) for a discussion. 33 Lopez & Elzière (2017, p. 6) 34 Cicogna & Bosinelli (2001), LaBerge & DeGracia (2000), Occhionero & Cicogna (2011). 35 Windt (2010, p. 301) 36 See Millière (2017) and Millière et al. (2018) for a detailed discussion of the relevant data. 37 Millière (2017). 38 Studerus, Gamma, & Vollenweider (2010). 39 Schmidt et al. (2012; 2013). 40 Bernasconi et al. (2014), Kometer et al. (2012), Preller et al. (2016), Pokorny et al. (2017). 41 Schmid et al. (2015), Carhart-Harris, Kaelen, et al. (2016), Carhart-Harris, Muthukumaraswamy, et al. (2016), Kraehenmann et al. (2017), Liechti, Dolder & Schmid (2017), Preller et al. (2017). 42 Report from online survey, quoted in Millière et al. (2018). 43 Timmermann et al. (in preparation). 44 For example, some subjects report temporarily regaining awareness of internal bodily sensations only when they remember to breathe, that is when they make a voluntary effort to take a deep breath. 9 possibility. The first comes from the experience of deafblind people, namely individuals who have little to no ability to hear or see45. Because they lack distal perceptual capacities, one can expect deafblind people to lack the kind of self-locating content that hearing and sighted individuals normally have. Nonetheless, tactile, proprioceptive and vestibular signals can provide some information about one's location with respect to one's environment. In order to shed light on this matter, I conducted a written interview with a deafblind individual (MVS) recruited online. MVS was born profoundly deaf with no residual ability to hear (unless she uses cochlear implants), and later became legally blind as a result of Usher Syndrome Type 1, which eventually reduced her visual field to a mere 5° in the left periphery. MVS mentioned that in ordinary experience, she relies on a mental "picture" of her environment. Since she only started losing sight as a teenager, she has kept the ability to mentally visualise the approximate distance and location of objects relative to herself both in familiar and unfamiliar environments, by touching reference points around her and/or with the help of a support worker describing the scene in tactile sign language. However, MVS did describe a commonly occurring experience in which she appears to completely lose awareness of her spatial location, when she takes a relaxing bath after removing her cochlear implants: Doing nothing but relaxing in the bath I always found I became lost as in relation to where I was... It is a feeling of being there but not there... You are here but not here. You are just existing... [I]f only for a short time I do lose the spatial awareness of the bath... [S]lowly the whole world vanishes... I have no sense of being present in any environment, the disconnect from all is like unplugging from the world... It is like being in a void, a nothingness that is just outside our reality, and I slip into the void when I have a bath... Your sense of where you are... just disappear[s] to nothingness, the world becomes nothing... It is as if the subconscious decides that location is now not needed and turns off the GPS area of the mind.46 Interestingly, when this happens, MVS does not completely lose awareness of her body ("I am aware of my body and limbs in this situation"), although bodily sensations are impoverished and mostly reduced to occasional twitches47. The second relevant example comes from artificial sensory deprivation. Indeed, it is likely that the kind of experience described by MVS may also occur for hearing and sighted individuals in sensory deprivation environments, such as flotation tanks, in which visual, auditory, tactile, proprioceptive, thermal and vestibular signals are extremely attenuated. The combination of the lack of distal information, minimal tactile stimulation and minimal gravitational cues achieved through floating in the dark at body temperature should yield an experience lacking self-locating content48. Moreover, it has been suggested that bodily awareness may not completely subside even in these conditions49. In fact, a recent study of the therapeutic outcomes of sensory deprivation found that participants immersed in a flotation tank reported a significant increase in the intensity 45 See Dammeyer (2014) for an overview of deafblindness. 46 Unpublished data from written interview. 47 See the next section for a more detailed discussion of the waxing and waning of bodily awareness in MVS's experience. 48 See note 63 for anecdotal evidence from narrative reports of flotation tank users. 49 "[B]odily signals of interoceptive, vestibular, or proprioceptive origin are never completely disrupted, even in... sensory deprivation" (Faivre, Salomon, & Blanke, 2015, p. 25). While these signals themselves might never be completely disrupted, the subject's conscious awareness of them might subside in some cases – see for example my discussion of certain drug-induced states above. I do suspect that awareness of bodily signals (including interoception) can disappear, if only temporarily, in sensory deprivation environments (see sub-section 4.3 for a discussion). In other words, sensory deprivation might be able to induce states with or without bodily awareness, depending on a number of factors such as the duration of the deprivation and the attentional focus of the subject. 10 of cardiorespiratory sensations compared to controls50. This suggests that interoceptive sensations can subsist in the absence of spatial self-consciousness51. A third candidate for bodily self-consciousness without spatial self-consciousness is provided by certain meditation practices. There is preliminary evidence that expert practitioners of mindfulness meditation may be able to achieve an altered state of consciousness in which they lack self-locating content52. In a recent study, a highly experienced meditator (subject S) with around 20,000 hours of practice described such a state in terms that are reminiscent of MVS's report: "I don't have any kind of sense of location... I have no idea where I am... I'm not there basically, just world, so there's no real location"53. Another study of long-term mindfulness meditation practitioners found that some of them were able to induce what was described as a state of "spacelessness"54. Yet given the focus of meditation on monitoring bodily sensations, it is unlikely that such states completely lack bodily awareness. For example, subject S reported that "there is a kind of very light sense of body in this experience"55. At the very least, it is plausible that some form of interoceptive awareness remains present in the background of the experience, even when the sense of self-location is lost56. In conclusion, I believe there is credible evidence that bodily self-consciousness may occur in the absence of spatial self-consciousness. This casts doubt on the claim that being aware of one's location in egocentric space is the simplest form of self-consciousness, if this is meant to entail that it should be both sufficient and necessary for self-consciousness. However, the arguments of this sub-section (4.2) and the previous one (4.1) do not yet rule out a 'disjunctive' version of the scaffolding model, according to which the first level of self-consciousness involves either bodily or spatial self-consciousness, while the second level involves cognitive self-consciousness in addition to either of the other modes. I will now turn to empirical evidence that challenges this possibility. 4.3 Cognitive self-consciousness without bodily or spatial self-consciousness In light of the cases I have already discussed, it seems possible to think about oneself without being aware of one's body. During asomatic OBEs, for example, subjects do not lose the ability to think of themselves and self-ascribe certain properties. In fact, in one of the earliest reports of OBEs, the neurosurgeon Wilder Penfield recounts that a patient whose temporal lobe he was electrically stimulated suddenly screamed "Oh God! I am leaving my body"57. There is no reason to believe that cognitive self-consciousness is impaired during such phenomena. Admittedly, the cases of bodiless dreams and drug-induced states are more complex. Although I am not aware of actual reports of lucid bodiless dreams, this certainly seems to be a possibility; a lucid dreamer should be able to entertain de se thoughts within a bodiless dream. In drug-induced states, the ability to think about oneself can be impaired concurrently with impaired bodily awareness58. This does not have to be the case however: some instances of drug-induced experiences of disembodiment, induced for example by ketamine59, do not seem to necessarily impair the ability to have de se thought. Overall, these different cases suggest that the occurrence of cognitive self-consciousness does not depend on that of bodily self-consciousness. It also seems possible to think about oneself without being aware of one's location in egocentric space. Cases of extreme sensory deprivation are likely 50 Feinstein et al. (2018). 51 It is debatable, however, that having interoceptive sensations is sufficient to be aware of one's body as one's own. For example, de Vignemont argues that "interoceptive feelings... cannot ground the distinction between self and nonself" (2018, p. 269). 52 See Millière et al. (2018) for further discussion. 53 Ataria et al. (2015, supplementary material). 54 Berkovich-Ohana et al. (2013). 55 Ataria et al. (2015, supplementary material). 56 Again, one could dispute that interoception is sufficient for bodily self-consciousness. In any case, MVS's experience is not vulnerable to this concern. 57 Penfield (1955) 58 See Millière et al. (2018) for discussion. 59 Muetzelfeldt et al. (2008). 11 candidates for the occurrence of de se thoughts in the absence of self-locating content. Indeed, there is no evidence that the loss of self-locating content in such states impairs the ability to think about oneself. Similarly, there is no reason to think that the kind of experience described by MVS in deafblindness is incompatible with the occurrence of de se thought, such as the ability to wonder where one is located with respect to one's environment. In order to rule out a disjunctive version of the scaffolding model, however, one needs to motivate the claim that cognitive self-consciousness may occur when neither spatial nor bodily selfconsciousness occurs. This project can be traced back to the so-called "Flying Man" thought experiment conceived by the Persian philosopher Ibn Sīnā (c. 980-1037), also known as Avicenna in the Christian world. In an influential passage from his psychological treatise On the Soul, Ibn Sīnā asks the reader to imagine what it would be like to be flying in the void without any kind of sensory input60. He goes on to speculate that one would still be conscious of oneself in such conditions, through an intellectual form of self-consciousness. In a recent article, Dainton imagines a similar scenario with a deaf and blind puppy "in outer space, floating mid-air, weightless, in a well-heated chamber"61. He suggests that the fictional puppy would lack any sense of its location with respect to its environment. As he acknowledges, however, the animal would arguably still be conscious of its body through interoception. Ibn Sīnā does insist that the limbs of the Flying Man should not be touching, to avoid the occurrence of tactile sensations; but one can similarly hypothesise that the Flying Man would not lack the ability to feel internal bodily sensations. As previously mentioned, actual sensory deprivation in flotation tanks – which can be seen as an attempt to emulate Ibn Sīnā's thought experiment in the real world – may not only preserve awareness of interoceptive signals, but even temporarily increase it62. Nonetheless, I believe there are reasons to think that bodily awareness and self-locating content can both be missing in certain cases. Firstly, as I have already suggested, it is not obvious that bodily awareness is as pervasive as it might seem even in ordinary experience, during mundane episodes of mind-wandering or task-related absorption. If bodily awareness dynamically waxes and wanes as a function of the allocation of attention, it is reasonable to suppose that a subject deep in thought in a flotation tank might, if only for a short time, lose any awareness of her body. Even if one remains unconvinced by the hypothesis that mind-wandering does suppress bodily awareness, anecdotal evidence suggests that artificial sensory deprivation may induce conscious states in which both self-locating content and bodily awareness are missing – including interoception. Indeed, many users of flotation tanks report losing awareness of their body and location in space during prolonged sessions, in a state often described as intermediate between wakefulness and sleep63. Secondly, it seems that experiences lacking both spatial and bodily modes of self-consciousness may occur for deafblind people in certain conditions. When I asked MVS to elaborate about her experience of disconnection when taking a relaxing bath, she qualified her statement that she could feel her body during this experience: 60 Ibn Sīnā, Shifā': Fī al-nafs 5.7. For a historical discussion see Kaukua (2015, p. 35). 61 Dainton (2016, p. 139). See also Dennett (1993, p. 4) for a similar thought experiment about a "deafferented" brain in a vat whose subject is "blind, deaf, completely numb, with no sense of [their] body's orientation". 62 Feinstein (2018). 63 "I... just flew away into nothing... and could not feel whether I was in the tank or where I was" (Kjellgren, Buhrkall, & Norlander, 2010, p. 1252); "I'd reached a stage where I literally couldn't feel my body or tell if my eyes were opened or closed" (Allison P. Davis for the The Cut, 20 August 2015, https://www.thecut.com/2015/08/isurvived-my-terrifying-hour-in-a-float-spa.html); "I felt nothing. After some time, I became acutely aware that I could not feel my body" (Richard A. Friedman for the New York Times, 29 December 2016, https://www.nytimes.com/2016/12/29/opinion/sunday/whos-in-charge-the-body-or-the-brain.html). As I mentioned in note 49, the experience of sensory deprivation can be modulated by a number of factors, and it is possible that interoceptive awareness remain present in some cases and completely subside in others (e.g. for prolonged sessions in flotation tanks, when subjects stop attending to their body). In any case, as I also mentioned, there is some debate about whether interoception is a form of bodily self-consciousness. More credible data from controlled experiments is needed to draw stronger conclusions on the full spectrum of experiences that can be induced through artificial sensory deprivation. 12 Thinking more about this – where I say that I can feel my body – it's more of a split second of awareness, it is also only if some part of my body twitches... [I]t is a passing moment of awareness. You're not there in your body anymore... till your body does a natural twitch... The boundaries of my body vanish when [I am] cocooned in the water, the only time I become aware is when I twitch.64 While occasional twitches are enough to make MVS aware of her body when she takes a bath, these are only transitory episodes of bodily awareness. It seems that most of her experience of disconnection involves neither awareness of her location with respect to her environment, nor awareness of her body. Does it remain possible for someone who undergoes such an experience to think about themselves? While evidence is scarce on this point, I see no good reason to presume otherwise. For example, MVS appears to retain some ability to think about what is happening to her when the feeling of disconnection occurs ("I am aware of what happens to some degree"), which should include the ability to form de se thought. Likewise, there is no reason to think that artificial sensory deprivation necessarily disrupts the ability to think about oneself once one's body and location have faded away, especially if mind-wandering – which frequently involves de se thought – potentiates the suppression of bodily awareness and self-location. In an influential paper on the first person, Anscombe considers what would happen if she was immersed in a flotation tank. She speculates that even if she lost awareness of her body, she would still be able to form de se thoughts such as "I won't let this happen again!". She adds that "if the object meant by 'I' is this body, this human being, then in these circumstances it won't be present to my senses; [but] I have not lost my 'self-consciousness'" – precisely because she would still be thinking about herself65. There are perhaps a few other cases in which de se thoughts might occur without either bodily or spatial self-consciousness. There is some evidence that episodes of conscious thought might occur during dreamless sleep, without the sensory phenomenology characteristic of dreaming66. In this phenomenon, known as "sleep thinking", the kind of sensory information needed to be aware of one's body or location in egocentric space is simply not available. Nonetheless, it seems that subjects in these states can form reportable thoughts in abstracto, without the sensory background of ordinary experience. While there is no evidence, to my knowledge, regarding the specific occurrence of de se thought in dreamless sleep, it cannot be ruled out if sleep thinking does occur. Finally, certain drug-induced states might also involve cognitive self-consciousness without either bodily or spatial self-consciousness. There is converging evidence that certain psychedelic drugs such as 5-MeO-DMT can suppress both one's awareness of one's body and one's awareness of one's location in egocentric space67. Moreover, anecdotal evidence from narrative reports suggests that in some cases, de se thoughts might occur in these states, such as the thought that one is dying68. Overall, these data points raise a serious challenge to the disjunctive version of the scaffolding model. 4.4 Pre-reflective self-consciousness Before closing the discussion of the scaffolding model, I will briefly consider the suggestion that the "most minimal" form of self-consciousness is not bodily or spatial self-consciousness, but a 64 Unpublished data from written interview. 65 Anscombe (1975, p. 57). Although Anscombe does not discuss spatial self-consciousness in this example, one could similarly imagine thinking "I won't let this happen again!" after losing awareness of one's body and location in a flotation tank. 66 See Windt et al. (2016). 67 See Millière et al. (2018) for a discussion. 68 Here are two examples from a curated database of narrative reports of drug-induced states (retrieved from Erowid.com): "[I]t felt as though there was, at that point, no longer any difference between me and the room... I was suspended in space, surrounded by emptiness infinite in all directions. I began to think about the cliché routine of asking myself about the imminence of my own death." (report #88358 from a user of 5-MeO-DMT); "I finally lose consciousness of my surroundings... I can remember in my mind continuing to say to myself, 'just let go'... until there was pure darkness. At that moment, I thought I was dead. I had no senses for these few seconds." (report #94141 from a user of 5-MeO-DALT). These are of course anecdotal reports and should be treated with caution. 13 pre-reflective form of self-consciousness that is constitutive of consciousness in general. According to this claim, which is arguably a version of the scaffolding model, all conscious mental states involve pre-reflective self-consciousness (PRSC), while only some conscious mental states also involve more sophisticated forms of self-consciousness like those I have discussed so far. On this view, principally developed within the phenomenological tradition69, "there is a constitutive link between phenomenal consciousness and self-awareness"70. Philosophical discussions regarding PRSC are complex and ramified, and I cannot reasonably attempt to provide an exhaustive analysis of this notion in this article71. I will simply suggest that PRSC is not in fact a form of self-consciousness as I have defined it in this article – a consciousness of oneself (as oneself). Indeed, PRSC refers to "the fact that experiences are... present [to their subject] in a distinctly subjective manner, a manner that is not available to anybody else"72; that is, "our acquaintance with our own experiential life differs from the acquaintance we have with the experiential life of others and vice versa"73. All conscious mental states constitutively involve PRSC insofar as they constitutively contribute to the overall phenomenology of their subject – and not to anyone else's. Dan Zahavi occasionally puts this point by saying that whenever a subject S is in a conscious mental state M, S is aware of M in a way in which no one else is aware of M74. As he emphasizes, however, "being aware of one's experiences when they occur is [not] tantamount to being aware of oneself as a (secondary) object [of one's experience]"75. Thus, I take it that PRSC is not a form of self-consciousness as I have used the term throughout this article: it does not refer to the subject's awareness of herself as herself, but to the subject's awareness of her experience (or to the experience's constitutive contribution to the subject's overall phenomenology)76. Consequently, the claim that PRSC is a necessary component of consciousness does not in fact support a version of the scaffolding model of self-consciousness77. 4.5 Beyond the scaffolding model The upshot of the dissociations between three modes of self-consciousness is that the idea that there is a "simplest form of self-consciousness", namely a feature of experience both sufficient and necessary for self-consciousness, is challenged by empirical evidence. Bodily self-consciousness is not necessary for self-consciousness, since both spatial and cognitive self-consciousness can occur in its absence; neither is spatial self-consciousness necessary, since bodily and cognitive selfconsciousness can occur when it is missing. Although I have not discussed this possibility here, there is also evidence that cognitive self-consciousness is not necessary for self-consciousness78. Unless there exists some other mode of self-consciousness that can be shown to be necessary for 69 See Zahavi (2004, 2005, 2014) and Gallagher & Zahavi (2005) for historical overviews of this proposal articulated to contemporary discussions. 70 Zahavi (2018, p. 707). 71 See Kriegel (2009) and Zahavi (2014) for book-length treatments of these notions. For a critical perspective, see Guillot (2017) and Salje & Geddes (forthcoming). One potential issue with the discussion of notions such as PRSC and other related constructs is that their meaning varies across authors and publications. 72 Zahavi (2014, p. 41). 73 Zahavi (2014, p. 24). 74 See also Kriegel (2009). 75 Zahavi (2018, p. 706). 76 As Gurwitsch (1941) puts it, PRSC is a "non-egological" notion of self-consciousness. A proponent of PRSC could argue that I beg the question against the scaffolding model by excluding the "non-egological" notion from my understanding of self-consciousness. In my opinion, self-consciousness needs to be disambiguated before the scaffolding model can be assessed. 77 A few authors do claim that all experiences involve a form of self-consciousness construed as a consciousness as of oneself (Sebastián, 2012). Although I cannot discuss this proposal within the space of this article, I think it is at odds with phenomenology, especially when it comes to radically altered states of consciousness such as drug-induced ego dissolution (see Millière, 2017). 78 There is evidence that flow states (Csikszentmihalyi, 1990) and meditation (Millière et al., 2018) may exhibit bodily self-consciousness without cognitive self-consciousness, while certain drug-induced states may exhibit spatial selfconsciousness without cognitive self-consciousness (Millière et al., 2018; Timmermann et al., in preparation). 14 self-consciousness, there is simply no reason to believe that there is a simplest form of selfconsciousness in the relevant sense. In addition, the empirical dissociation between cognitive selfconsciousness and both bodily and spatial self-consciousness also raises a serious challenge to the weaker disjunctive version of the scaffolding model. Overall, this suggests that the scaffolding model does not offer a credible account of levels of self-consciousness79. This does not bode well for the idea that two creatures can be ranked according to the degree to which they are self-conscious. Admittedly, my criticism of the scaffolding model does not rule out the weaker claim that there are relative degrees of self-consciousness following a partial ordering between global states. For example, one could claim that the more modes of self-consciousness a subject is in at a particular time, the more self-conscious she will be overall. Accordingly, a subject who is conscious of herself in one way would be less self-conscious than a subject who is conscious of herself in two ways, the latter would herself be less self-conscious than a subject who is conscious of herself in three ways, etc. While this proposal is coherent, it seems ad hoc. It is not obvious to me why a subject who is aware of her location in egocentric space and thinking about herself during an out-of-body experience should be said to be less self-conscious than a subject who is aware of her body and location in space while having a de se thought. By analogy, it is unclear why someone who sees a particular apple would be less conscious of that apple than someone who sees and touches it at the same time. Conclusion It is not easy to make sense of the claim that self-consciousness comes in degrees. The most interesting account of self-consciousness as a gradable property is arguably the scaffolding model, according to which one-way dependence relations hold between different ways of being selfconscious. The scaffolding model allows for an ordering of global states of consciousness according to the degree to which their subjects are self-conscious, which is determined by the modes of self-consciousness they instantiate. However, I have argued that this model does not sit well with empirical evidence from a variety of conditions in which different modes of selfconsciousness are not instantiated. Rather than thinking of self-consciousness as graded on a single scale, it seems preferable to think of it as a multidimensional construct, where each mode of selfconsciousness constitutes a different dimension80. Future research could assess to what extent these different dimensions are themselves gradable, whether the relevant scales are discrete or continuous, and what kind of psychometric tools could be used to measure them81. 79 One could object that the various empirical cases I have discussed only show that spatial self-consciousness or bodily self-consciousness (depending on which is taken to be more fundamental) can be strongly "disrupted" or "diminished", rather than altogether missing. I see two issues with this proposal. First, it seems ad hoc, given that the interpretation I have given is the most straightforward. For example, MVS's description of her experience of disconnection is unambiguous regarding the loss of any awareness of her location with respect to her environment, and is consistent with the lack of relevant sensory signals from visual, auditory, vestibular and tactile cues in this situation. Second, if the scaffolding model was correct, one would expect the "weakening" of the bottom level of the scaffolding, as it were, to have an effect on the top level. In other words, it is unlikely that the profound disruption of bodily or spatial selfconsciousness would have no consequence on one's ability to form de se thought. And yet, as I have suggested, there are reasons to believe that cognitive self-consciousness may occur in sensory deprivation, deafblindness, sleep thinking and drug-induced states in which bodily and spatial self-consciousness are thoroughly impaired. 80 See Millière et al. 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