## 1. The body from the inside



The body is a material entity located in space and time in the same
way as a rock, a tree or a bird. But do we perceive and experience our
body like those other objects? Most philosophical interest for bodily
awareness has come from its peculiarities. It is precisely because we
assume that we are aware of our body differently from other objects
that it raises many questions. But what makes it unique? The most
intuitive answer is that it bears a special relation to the self, and
to self-awareness. As noted by O'Shaughnessy (1980: vol. 1, p.
138), 



> 
> 
> Now there is every reason for expecting it to be a *highly unusual
> relation*. For we are talking about the epistemological link
> between a man and in all probability himself qua material object! and
> in any case the one object in the universe that is his own body. Is
> not that likely to be unusual? 
> 
> 
> 



However, although introspectively familiar, it is hard to exactly
pinpoint the nature of the specific relation. One way to characterize
it is to say that many bodies, including our own, can appear to us
from the outside but only our own body appears to us *from the
inside*. Most definitions of the inside mode then amount to little
more than list the internal ways of gaining knowledge about our body.
However, it is not clear that they form a unified category. What they
have in common is that they seem to all guarantee that bodily
judgments are immune to error through misidentification relative to
the first-person. But are body senses the only ones to guarantee
bodily immunity and are bodily judgments still immune when the grounds
of bodily awareness are multimodal?


### 1.1 Varieties of bodily experiences



Most discussions on bodily sensations focus on the privileged relation
they have with the subject's body and assume a unified account
for bodily awareness, as if it made no difference whether one feels
pain, touch or hunger. However, there are clear physiological,
phenomenological, and epistemic differences among them. Here is a
brief overview of the specificities of each type of bodily
sensations:



*Tactile sensations* are mediated by cutaneous mechanoreceptors
(see Entry on Touch). Touch carries information both about the object
one is in contact with and about the body part in contact (Katz 1925;
Fulkerson 2014; Richardson 2013; Vignemont and Massin, 2015). For
some, it is the most important sense because it gives us an
experiential access to the reality of the world we are in contact
with: 



> 
> 
> There is no commoner remark than this, that resistance to our muscular
> effort is the only sense which makes us aware of a reality independent
> from ourselves. (James 1880: 29; see also Armstrong 1962; Condillac 1754; Maine de
> Biran, 1812) 
> 
> 
> 



However, there is a large debate in the literature about how to
distinguish touch from other senses. For instance, are thermal
sensations tactile sensations or not? Should one distinguish sensory
touch and affective touch (McGlone et al. 2014)?



*Proprioceptive experiences* provide information about the
position and movement of the body, although the notion of
proprioception is sometimes enlarged to refer to all bodily sensations
(Bermudez 1998). The mechanisms of proprioception include
muscle spindles, which are sensitive to muscle stretch, Golgi tendon
organs, which are sensitive to tendon tension, and joint receptors,
which are sensitive to joint position. One question is whether these
signals give rise to sensations or not (Anscombe 1962).



The *sense of balance* depends on vision, touch, and more
importantly on the *vestibular system* in the inner ear, which
provides information about the balance of the body. It includes three
roughly orthogonal semicircular canals, which are sensitive to motion
acceleration as our head moves in space, and two otolith organs, which
are sensitive to the pull of gravity. It replies to two questions: (1)
'Which way is up?' and (2) 'Where am I
heading?'. As for proprioception, one may question whether there
is a phenomenology of balance. Besides cases of dizziness, there seems
to be indeed a paucity of vestibular experiences in normal consciousness.
The vestibular system has been ascribed a major role for self-location
by anchoring the subject to her location and in orienting the subject
in the world (Wong 2017). 



*Pain* raises many challenges for philosophers (see Pain
entry), and the variety of painful experiences makes the problems even
more complex (Corns 2014). From a physiological level, we have
*nociceptors* on the skin that respond to dangerously intense
mechanical stimuli, to mechanothermal stimuli or to thermal and
chemical stimuli. According to the dominant theory, noxious signals
are inhibited, enhanced or distorted by various factors via a gating
mechanism at the level of the spinal cord that controls the amount of
signals from the periphery to brain structures and via a central
gating mechanism (Melzack & Wall 1983). A major issue is to
account for both the sensory component of pain, which represents the
felt location and intensity of the sensation, and for the affective
component, its unpleasantness, which motivates protective behaviors.
To do so, recent representationalist theories propose that pain has
evaluative content (Bain 2013) or imperative content (Klein 2015;
Martinez 2011; Hall 2008).



*Interoceptive awareness* provides information about the
physiological condition of the body in order to maintain optimal
homeostasis, namely, cardiovascular, respiratory, energy (feeding and
glucose), and fluid (electrolyte and water) balances. It has been
recently suggested that interoception plays a major role for grounding
the "bodily self" (Damasio 1999; Craig 2003; Seth 2013;
Tsakiris & de Preester 2018). There is, however, a debate on how
to define interoception (Ceunen, Vlaeyen, & Van Diest 2016). Does
it include only information about the homeostatic state of the
organism, as originally proposed by Sherrington (1906), or any
sensation with an affective component, thus including pain and
affective touch, as recently assumed by Craig (2003)?



David Armstrong (1962) has been the only one to offer a taxonomy of
all these bodily experiences. He draws a first contrast between
*bodily sensations* and bodily *feelings*. Sensations,
such as touch and pain, are local whereas feelings, such as thirst,
hunger, fatigue, sleepiness, dizziness, and shortness of breath, are
global. For instance, you can distinguish the local sensation of
pinprick at the tip of your index finger with the diffuse feeling of
fatigue in your whole body. Or consider the case of thirst: it reveals
the general state of the entirety of your body missing water. More
generally, interoceptive feelings inform us about the welfare of the
organism as a whole. Their spatial principle of organization is thus
holistic. Within the category of bodily sensations, Armstrong further
distinguishes *transitive* and *intransitive* bodily
sensations. One experiences a mind-independent object in transitive
sensations, as in touch, but it does not seem so in intransitive ones,
as in pain. As described by Reid (1764: 56), 



> 
> 
> If a man runs his head with violence against a pillar ... he
> feels nothing in the stone but feels a violent pain in his head. It is
> quite otherwise when he leans his head gently against the pillar, for
> then he will tell you that he feels nothing in his head, but feels
> hardness in the stone.
> 
> 
> 



To Armstrong's list, one may add what has been called
existential feelings (Ratcliffe 2008; Billon 2015). All those bodily
sensations listed above describe the 'anecdotal' state of
the body, so to speak, that is, the state of the body that keeps
changing (e.g., its posture, its temperature, its movement, and so
forth). However, there is another aspect of bodily awareness, which is
less directly connected to sensory receptors, and which concerns the
enduring state of the body, its 'fundamental' properties.
Imagine having a terrible nightmare in which you are floating in the
sky but then suddenly start falling down. After waking up, you become
aware that you are alive and that all your limbs are intact. You are
aware of your body being here in your bedroom, no longer floating up
in the sky. You also regain awareness that this body has two legs and
two arms that can cycle and swim, but that cannot fly. You are finally
aware that this body is of a highly peculiar significance for you: it
is yours, or maybe even it is you. It includes the sense of bodily
presence (awareness of one's body as being here), the sense of
bodily ownership (awareness of one's body as being one's
own), and the sense of bodily agency (awareness of one's bodily
capacities for action). These senses are rarely at
the forefront of consciousness because they normally do not vary, and
thus do not attract attention.


### 1.2 Immunity to error through misidentification



Despite their differences, all bodily experiences seem to display the
same epistemological signature: they ground the immunity to error
through misidentification relative to the first-person of bodily
self-ascriptions. Self-ascription of a property is said to be immune
to error if and only if one cannot rationally doubt who instantiates
the property when one has gained information about the property in the
appropriate way (although one can be mistaken about the property that
one ascribes to oneself) (Shoemaker 1968; Evans 1982). For instance,
if I think that I am anxious because I feel anxious, my thought is
immune to error through misidentification of the subject. But if I
think that I am anxious because my psychoanalyst told me so, my
thought is not immune to error. Indeed, the psychoanalyst may have
confused me with another patient, who is the person suffering from
anxiety. To be immune, my thought must be grounded in introspection,
that is, on a way of gaining information about one's mental
states *from the inside*. The question is whether the
self-ascription not only of mental properties, but also of physical
properties (such as body posture) can be immune to error in such a
way. Consider the following example. I form the judgment that my legs
are crossed while I am seated around a small table with several other
persons. Can I rationally doubt that they are mine? If I make this
judgment on the basis only of my seeing legs, then I can confuse my
legs with the legs of the person seated next to me. By contrast, if I
make this judgment because I feel my legs as being crossed, then the
answer is negative. The inside mode of body senses guarantees immunity
to error (IEM) because they provide a privileged informational access
to one's own body only. Because of this privileged relation, the
judgement "my legs are crossed" is not grounded in the
judgement "these legs are crossed" and in the
identification "these legs are mine". Proprioceptive
experiences suffice to justify bodily self-ascriptions such that no
intermediary process of self-identification is required
(Bermudez 1998; Brewer 1995; Cassam 1995; Evans 1982).



Bodily IEM has been taken by some as evidence that the self is
embodied. For instance, Evans (1982) and Cassam (1997) use bodily IEM
as an argument against the Cartesian view of the self. In a nutshell,
one can self-ascribe bodily properties as well as mental properties to
the self without self-identification. Hence the object of such
judgments, the self, is not a Cartesian ego, but a bodily subject of
both mental and physical properties. However, others wonder if one is
entitled to draw such a metaphysical conclusion from the
epistemological fact of bodily IEM (Chen 2011; J. Smith 2006). Some
further deny that bodily self-ascriptions display the same type of IEM
as mental self-ascriptions (Shoemaker 1968; Coliva 2012). The IEM of
pain self-ascriptions, for instance, is said to be absolute or
logical. On this view, there is no possible world in which one can
feel pain and be mistaken about who is feeling pain. By contrast, one
can easily conceive a case of a cross-wiring scenario such that A is
connected through A's proprioceptive system both to A's
body and to B's body. Then A can feel B's legs being
crossed. The question then is whether this cross-wiring scenario
invalidates bodily IEM. One can also wonder about actual breach of
bodily IEM, such as the rubber hand illusion in which subjects
self-ascribe a hand that does not belong to them (Mizumoto &
Ishikawa 2005). However, one might reply that none of these thought
experiments or bodily illusions show that bodily sensations fail to
guarantee IEM because the epistemic grounds of bodily self-ascriptions
in these cases differ from ordinary somatosensory judgments (Salje
2017; Vignemont 2012). At most, they show that bodily IEM is only
*de facto* (Evans 1982).



To recapitulate, although the debate of IEM has mainly focused on the
ascription of mental states, the ascription of bodily properties
raises three major questions: (i) Can bodily self-ascriptions be
immune to error, and if so, what are the appropriate grounds that
secure bodily IEM? (ii) Is bodily IEM of a different type from mental
IEM? (iii) Does bodily IEM reveal the bodily nature of the self?


### 1.3 The body from the outside



As just seen, it is generally assumed that vision, and other external
senses, do not guarantee bodily IEM. Ernst Mach famously reported
stepping onto a bus and noticing a man who looked like a shabby
pedagogue. In fact, he was seeing himself in a large mirror at the far
end of the bus (Mach 1914). Conversely, if we see a broken arm, we can
mistake it for our own, although it is another person's arm that
is mixed up with ours (Wittgenstein 1958). On the basis of such
examples, it is said that no judgement based on external senses is
immune to error through misidentification. There is a gap between
visually knowing that a body is *F* and visually knowing that it
is my own body that is *F*. Consequently, when people discuss
bodily awareness, they rarely mean the visual awareness one can have
of one's body.



Some, however, are opposed to such a contrast between external senses
and body senses. For instance, the psychologist Gibson (1979) argues
that even while looking at the external world, our visual experiences
carry information about our own body: 



> 
> 
> I maintain that all the perceptual systems are propriosensitive as
> well as exterosensitive, for they all provide information in their
> various ways about the observer's activities... Information
> that is specific to the self is picked up as such, no matter what
> sensory nerve is delivering impulses to the brain. (Gibson 1979: 115)
> 
> 
> 
> 



The fact is that when I have the visual experience of a tree in front
of me, I cannot have the following doubt: "someone is standing
in front of a tree, but is it I?" (Evans 1982: 222). Evans
concludes that visual experiences of the external world from an
egocentric perspective guarantee the IEM of self-locating judgments
(Cassam 1995; Bermudez 1998; Peacocke 2012; Schwenkler 2014).
Likewise, one may argue that visual experiences *of the body*
could also guarantee IEM in some ecologically valid situations (Evans
1982: 220 fn 26; Peacocke 2012).
Proprioception guarantees bodily IEM because of some biological facts
about the human body (i.e., the proprioceptive neural system is
connected only to one's own body). In the same vein, one may
suggest that there are some other basic biological facts that secure
the link between certain visual contents and one's own body. For
instance, I can see my nose if I close one eye and I cannot doubt that
this is my own nose when I see it from this specific angle. 



The fact that the inside mode exclusively results from body senses,
with no influence from external senses, has also been questioned by
recent empirical evidence (Stein & Meredith 1993; Ernst 2006; van
Beers et al. 1999; Welch & Warren 1980). Information from one
modality can affect information in another modality. Multisensory
effects occur very early on in sensory processing and they are often
automatic and mandatory. Consequently, the 'normal' way of
gaining bodily self-knowledge is not on the basis of body senses only,
but rather on the basis of their integration with vision. Take the
rubber hand illusion, which results from the incorrect integration of
somatosensory information and visual information about the rubber
hand. It induces not only a sense of ownership for the rubber hand,
but also proprioceptive drift (i.e., one mislocalizes one's hand
in the direction of the location of the rubber hand) and referred
sensation of touch (i.e., one feels touch on the rubber hand). It can
be explained by three major facts about the sensory systems. First,
optimal estimates of bodily properties require combination of
information from various sensory channels. Second, vision can dominate
over proprioception and touch because it often offers more accurate
and precise spatial information. Third, visual information can affect
the phenomenal content of bodily experiences. What we *feel* is
determined not only by information from body senses, but also by
information from external senses. Our access to the intrinsic
properties of our body is also partly based on vision. Although
O'Shaughnessy (1989: 56) claims that that our body image is
nothing more than a collection of information from body senses, it has
been found that blind individuals have a less accurate representation
of the size of their body parts compared to sighted individuals
(Kinsbourne & Lempert 1980: 37). The fact is that vision is the
only sensory modality that can directly and reliably (though not
perfectly) process size information (Longo & Haggard 2010). As
concluded by the neurologist Schilder (1935: 38) a long time before
multisensory research had started to take off: 



> 
> 
> It is not the case that the schema of the body has two different
> parts, the one optic and the other tactile. It is in essence a
> synaesthesia (...) The synaesthesia, therefore, is the normal
> situation.
> 
> 
> 



The notion of multimodality has become of interest to philosophers
only recently (Bennett and Hill, 2014; O'Callaghan 2020).
Unfortunately, there is already little agreement in philosophy on the
way to individuate the modalities themselves, let alone on how to
understand multimodality. One crucial question is whether these
multisensory effects show that vision plays only a *causal*
role in fixing the spatial content of bodily experiences or whether
bodily experiences are *constitutively* multimodal (Vignemont
2014). One may also ask whether some features can be represented only
thanks to multisensory integration (Briscoe forthcoming). A final
question is whether multimodality comes at the cost of bodily IEM. If
bodily self-ascriptions are grounded not only in the body senses,
which secure IEM, but also in vision, which does not always guarantee
IEM, then can one still claim that bodily self-ascriptions are immune
to error?


## 2. The perceptual model of bodily awareness



The previous section highlighted that I am aware from the inside only
of my own body. Does it prevent bodily awareness to be perceptual? Do
the body senses qualify as sensory modalities? Aristotle lists only
five of them (sight, hearing, touch, olfaction, smell) and if we added
the body senses, we would end up with possibly more than ten. The
question then is whether these so-called body senses behave like
sensory systems that lead to perceptual experiences. At first sight,
it may seem that some types of bodily experiences (like touch) are
perceptual, but not others (like pain, tickles, itches, thirst or
hunger) because they seem subjective and incorrigible (Aydede 2009).
But even if we focus on transitive bodily sensations, they differ from
visual experiences on several respects. They are continuously active
and they function largely outside consciousness. They often do not
appear to provide a sensory field in which perceptual objects can be
presented (Martin 1992, 1993; Wong 2017). Finally, there are important
epistemic asymmetries, bodily sensations appearing as less reliable
than visual sensations (Munro forthcoming).



Some of the worries outlined above may just evaporate if one gives up
theories of perception that treat vision as the paradigm of sense
perception. It is indeed controversial that every external sense,
including olfaction for example, meets all the constraints posited by
visuo-centric models and more recent works on perception go beyond
vision (e.g., McPherson (ed) 2011; Matthen (ed) 2015; Gatzia &
Broogard (eds) 2020). Furthermore, what implications, if any, do
multisensory effects have for the perceptual debate? In brief, as
outlined in the previous section, I am aware that legs are crossed on
the basis of the integration between vision and proprioception. Does
the involvement of visual information suffice to make my sense of
posture perceptual?



This section will focus on four issues: the notion of the body as a
perceptual object, the spatial peculiarities of bodily awareness, the
alleged epistemic failure for bodily sensations to ground bodily
knowledge, and the relationship between bodily awareness and
action.


### 2.1 The body as a perceptual object



McGinn (1996: 8) claims: "bodily sensations do not have an
intentional object in the way perceptual experiences do". His
view is shared by many, for at least two reasons: (i) the body cannot
both anchor our perception of the world and be an object of perception
for risk of infinite regress; and (ii) the body senses do not need to
identify and reidentify the body since they give information about
nothing else.



The first objection comes from Merleau-Ponty (1945: 92), who claims:
"The body is not one more among external objects". He
draws the distinction between the objective body made of muscles and
bones, and the lived body (*corps propre*), that is, the body
that we experience in pre-reflective awareness. He argues that the
lived body is not an object that can be perceived from various
perspectives, left aside or localized in objective space. On the
contrary, it is the zero-point (Husserl 1913), from which one can see
the objective space. If one were to adopt an objective stance on the
lived body, then the objectified body could no longer anchor the way
one perceives the world. Likewise, Gallagher (2003) argues that bodily
experiences should not be understood in perceptual terms. Using
Wittgenstein's distinction between the self as a subject and the
self as an object, Gallagher argues that the lived body must be
conceived as subject. Only then can it ground our conscious experience
of the world. However, subjectivity is not incompatible with
intentionality. Arguably, one can perceive the self as a subject
(Bermudez 1998). Furthermore, the lived body can be a
perceptual object without being transformed into an object among
others. Dokic (2003), for instance, claims that bodily sensations
display a *special* kind of perceptual awareness, but it is
still perceptual.



The second objection against the perceptual model follows from
Shoemaker's (1994) standard model of perception. On his view,
one key condition of perception is that the way of gaining information
allows for identification and re-identification of the perceived
objects. The difficulty with the body senses is that they seem to give
access only to a single object, namely, one's body. Several
answers have been offered to this objection. For instance, Schwenkler
(2013) replies that the body senses still convey facts about different
objects insofar as they convey facts about different parts of the
body. It is not clear, however, whether this suffices to refute the
objection. Martin (1995), on the other hand, defends what he calls the
sole-object view, according to which bodily sensations are only about
one's body and when they are not, they are illusory or
hallucinatory. Still, on his view, this does not prevent bodily
sensations to be perceptual. One indeed experiences one's body
as a bounded object. By becoming aware of bodily boundaries, one then
becomes aware of a larger space that contains one's body as well
as other objects (see also Bermudez 1998).


### 2.2 The spatiality of bodily awareness



One can also question the perceptual character of bodily sensations on
the basis of their peculiar spatiality. We experience sensations
"at-a-part-of-body-at-a-point-in-body-relative-space"
(O'Shaughnessy 1980). In Bermudez's (2005) terms,
bodily sensations have both A-location (i.e., bodily frame of
reference independent of the posture of the body) and B-location
(i.e., external frame relative to the posture of the body). But how to
account for A and B-location? As Merleau-Ponty (1945: 98) warns,
"ordinary spatial relations do not cross" the experience
of the space of the body. It seems indeed that the way we experience
bodily space does not follow some basic spatial rules (Coburn 1966;
Vesey 1964; Margolis 1966; K. Baier, 1964; Holly 1986). For instance,
the pain that I feel in my thumb is not felt in my mouth when my thumb
is in my mouth (Block 1983). Nor does it seem to make sense to claim
that the pain in my thumb is far from the pain in my foot. How can one
envisage accounting for bodily space in terms of Cartesian reference
frame when one cannot provide a center of this frame, nor suggest axes
on which one could compute distances and directions (Bermudez
2005)? One may conclude that the claim that one feels pain *in*
the finger does not indicate the location of the sensation, but rather
the state of the finger (Noordhof 2001; for discussion see Tye 2002).
One may then question whether bodily
sensations themselves are intrinsically spatial. According to the
Local sign theory, as defended in the 19th century by psychologists
such as Wundt, Titchener and James, each sensible nerve gives rise to
its own characteristic sensation that is specific to the body part
that is stimulated but spatial ascription does not derive from the
spatial content of bodily sensations themselves. As described by James
(1890: 798), the Local sign theorists deny 



> 
> 
> that there can be in a sensation any element of actual locality, any
> tone as it were which cries to us immediately and without further ado,
> "I am here", or "I am there". 
> 
> 
> 



However, there seems to be no non-spatial differences between
sensations in one's right and left hands (Holly 1986;
O'Shaughnessy 1980; Margolis 1966; Coburn 1966). How then do I
feel the right or the left hand to be touched? And how to account for
sensations felt to be located in phantom limbs (K. Baier 1964)? It is
hard to explain spatial ascription of bodily sensations if bodily
sensations are not intrinsically spatial.



According to A. D. Smith (2002), perception requires the possibility
of achieving different perspectives on perceptible objects through
self-movement. This comes with the existence of perceptual constancies
(see Burge 2010 for the importance of perceptual constancies).
However, unlike other perceptual objects, the body cannot be felt from
different perspectives. Smith thus claims that bodily sensations are
mere sensations; they do not count as perceptual. Likewise, Matthen
(forthcoming) distinguishes within the sense of touch the tactual
sensation on one's skin and the haptic perception of the object.
These are two distinct types of experiences and only haptic
experiences are truly spatial, and thus truly perceptual. On the
contrary, Martin (1992) claims that there is no reason to draw a
distinction within tactile experiences: one can simply shift
one's attention from the bodily side to the exteroceptive side
of the same perceptual experience (see also O'Shaughnessy 1989).
Nonetheless, according to Martin (1992), touch differs from vision
insofar as it has no unified tactile field equivalent to the visual
field (see also Richardson 2013; Hopkins 2011).


### 2.3 Knowledge without observation



A different type of criticism of the perceptual model of bodily
awareness can be found in Wittgenstein (1978), and later Anscombe
(1962). They claim that the ability to report how the limbs are
located and how they move does not depend on sensations of position.
It thus differs from perceptual knowledge. I know that the sky is blue
in virtue of having a visual experience of the blueness of the sky but
I know that my legs are crossed independently of any sensation.
According to Anscombe, bodily knowledge cannot be grounded in
sensations because only sensations whose content is
"independently describable" can play an epistemic role.
The sense of position is thus what Anscombe calls a kind of knowledge
without observation: "It is without observation, because nothing
shews him the position of his limbs" (Anscombe 1957: 13).



The interpretation of the notion of knowledge without observation has
given rise to many debates. A first concerns Anscombe's
epistemological theory. Why do contents have to be independent to
ground judgments? The second problem is that it seems that her
argument ultimately relies on her phenomenological intuitions:
"no question of any appearance of the position to me, of any
sensations which give me the position" (Anscombe 1962). However,
one may question this claim on the basis of bodily illusions (Harcourt
2008; for a reply, McDowell 2011). For instance, if the tendon of the
biceps is vibrated, one can "feel" one's arm moving
though one knows the arm actually remains still. But does that suffice
to show that the sensation is independently describable? The problem
is that the notion of independent description is not clear. Why does
"the visual impression of a blue expanse" (Anscombe 1962:
57) qualify as independent but not the impression of one's arm
moving? It may sometimes be difficult to see why bodily awareness does
not fall into the same category as perceptual awareness.


### 2.4 Bodily awareness and action



Interestingly, both the phenomenological and the analytic traditions
that reject the perceptual model emphasize the role of action and
bodily know-how in their account of bodily awareness. Anscombe
describes knowledge without observation as a form of practical
knowledge. In a nutshell, knowing that your legs are crossed is not
feeling them to be crossed; it is knowing how to uncross them. Along
the same lines, Merleau-Ponty claims that the lived body is a space of
possibilities for actions. There is, however, a major difference. For
the phenomenologist tradition, what we *feel* is determined by
what we know how to do. For Anscombe, on the contrary, we do not feel
anything. Instead, one should say that what we *report* is
determined by what we know how to do. Furthermore, the emphasis on
action does not necessarily entail giving up the perceptual model of
bodily awareness and one should be careful distinguishing the two
claims.



Two main sensorimotor views of perceptual awareness have indeed
recently been proposed (see Entry on Action-based theories of
perception). According to the *enactive* approach, perceptual
experiences consist in sensorimotor expectations (O'Regan &
Noe 2001; Noe 2004; Hurley 1998; Thompson 2005;
O'Regan 2011). According to the dispositional approach, the
spatial content of perceptual experiences is made possible by
dispositions to act (Evans 1982; Brewer 1995; Briscoe 2009; A. J. T.
Smith 2009; Mandrigin forthcoming). Despite apparent similarities, the
two views make different claims. The enactive view aims to account for
consciousness in general, for its phenomenal character (O'Regan
2011). By contrast, the dispositional account applies only to
egocentric content. Furthermore, the enactive view makes a
constitutive claim: bodily experiences are inseparable from
sensorimotor expectations (for discussion of the constitutive claim,
see Block 2005). By contrast, the dispositional view does not claim
that the spatial content represents dispositions to act. It only makes
"a claim about the conditions under which a visual experience
will have such content" (Briscoe 2014: 208). 



A major challenge for the sensorimotor approaches is to account for
dissociations between perception and action. Such dissociations have
been found for vision, leading Milner and Goodale (1995) to propose
a dual model of visual processing: the ventral pathway is dedicated to
conscious perception whereas the dorsal pathway is dedicated to
visuomotor transformation perception. Dissociations have also been
reported in the case of bodily awareness. For instance, patients with
numbsense have no tactile awareness, but retain a surprising ability
to point to where they were touched (Paillard et al., 1983; see also
Anema et al. 2009 for further dissociation). The rubber hand illusion
as well indicates that bodily know-how can be at odds with bodily
experiences: participants accurately grasp the stimulated hand with
their opposite hand at its real location, and not at the illusory
location that they report (Kammers et al. 2009). Proponents of the
enactive view may have difficulties accounting for this type of
results, which indicate that sensorimotor knowledge is neither
necessary nor sufficient for bodily experiences (Vignemont 2011).
However, perception-action dissociations are less problematic for the
dispositional view (Mandrigin forthcoming).



We have just asked whether bodily awareness requires action. But one
may also ask whether action requires bodily awareness
(O'Shaughnessy 2000; Wong 2015). Action requires detailed
information about the long-term and short-term properties of the
bodily effectors. But does the information need to reach the threshold
of awareness, even at the margin? Action requires fast processing of
information, whereas bodily awareness takes time. Furthermore,
deafferented subjects who have no kinaesthetic and tactile awareness
of their body retain their ability to control their movements as long
as they receive visual feedback. Hence, kinaesthetic experiences do
not seem to be necessary for action. The body is not always
immediately present in all its details to the subject, even when
acting. Yet as Descartes pointed out, we are not like pilots in a
ship. The difference is that we are able to feel our ship from the
inside. Hence, there must still be a connection, still to be explored,
between our capacity to act directly with our body and our capacity to
feel our body from the inside (Wong 2015).


## 3. Mental representations and the body



When one discusses the relationship between bodily awareness and
action, one frequently appeals to the notion of *body schema*.
It is used, however, in many different ways. One of the main
controversies is whether it should be conceived as a specific type of
mental representation of the body. For Merleau-Ponty (1945), and more
recently for Gallagher (2008), the body schema should be conceived as
a sensorimotor function, devoid of intentional content. Their
definition is in line with a general trend in the last thirty years
that rejects the necessity to posit representations in the
mind (Gallagher 2008; Thelen & Smith 1994; Turvey & Carello
1995; van Gelder 1995; Thompson 2005; Zahavi & Parnas 1998). On
this view, representations are inadequate because they are too costly
and they are unnecessary because they can be easily replaced by
sensorimotor loops. The body ca be conceived as "its own best
model", to use Brooks's (1991) expression. If biological
systems only know what they need to in order to get their job done
(Clark 1997), is the body really something that the brain needs to
represent in this sense? All that may be needed is to pay attention to
it (Kinsbourne 1995; Hochstetter 2016).


### 3.1 Why body representations?



Until the end of the 19th century, bodily awareness was typically
understood in terms of a bundle of internal bodily sensations. Bonnier
(1905) first introduced the term *schema* to refer to the
spatial organization of these bodily sensations. But it was only in
Head and Holmes (1911)'s fundamental paper (discussed in the
next section) that one finds the first systematic analysis of the
way(s) the brain represents the body. They initiated what might be
called the *representationalist approach* to bodily awareness
(e.g., O'Shaughnessy 1980; Bermudez 1998; Vignemont
2018; Carruthers 2008;
Alsmith forthcoming; Murillo Lara 2018). Proponents of the
representationalist approach claim that in order to account for bodily
awareness one needs to appeal to mental representations of the body.
According to a minimal definition, a body representation is an
internal structure that has the function to track the state of the
body and encode it, that can misrepresent it and that can be decoupled
from it. It plays the role of model that represents in virtue of its
resemblance to the structure of the body (Alsmith forthcoming; Gadsby
& Williams 2018). Now the question is why positing such internal
models.



The first reason is to account for disturbances in bodily awareness.
Most of the literature on body representation can be found in patient
studies (Head & Holmes 1911; Lhermitte 1942; Cole & Paillard
1995, Schwoebel & Coslett 2005; Sirigu et al. 1991; Gadsby 2017).
With the help of the notion of body representation, and thus of body
misrepresentation, one can easily explain how the way the body is
experienced can be at odds with the physical reality of the body. On
the one hand, amputated patients can still feel the presence of their
absent limb because the physically missing limb is still represented.
On the other hand, patients with xenomelia can wish their perfectly
healthy limbs to be amputated because these limbs are not incorporated
in their body representation (Hilti & Brugger 2010).



The second reason focuses on the spatial organization of bodily
awareness (Bonnier 1905; O'Shaughnessy 1980, 1995; Murillo Lara 2018).
Over an extended period, all bodily experiences share the same spatial
content of the structural shape of the body. To account for this
commonality, O'Shaughnessy posits the existence of a long-term
body image that plays a structural role in spatially shaping bodily
experiences. One may then propose a hierarchical model of body
representations on the model of Marr's theory of vision: the
primal sketch, the 2.5D sketch, and the 3D sketch (Marr 1982). At each
step, more information is extracted from the original sensory input
until it switches from a viewer-centered perspective to an
object-centered perspective. At each stage, the representation of the
body gains in complexity and spatial richness (Longo 2017; Haggard et
al. 2017). The level of the primary somatosensory area (SI)
corresponds to the primal body sketch, which takes the shape of a
"homunculus" (Penfield & Rasmussen, 1950). Although it
generally follows natural anatomical divisions, associating cortical
areas to specific parts of the body, some are over-represented (e.g.,
hand), and others under-represented (e.g., torso). Furthermore, the
homunculus does not represent anatomical contiguity (e.g., the
hand-specific area is next to the face-specific area). Consequently,
the primal body sketch cannot play the role of supplying information
about body metrics and configuration (Medina & Coslett 2016). This
is done at a higher level of integration (integration among body parts
and among multiple sensory sources), at which a kind of 3D body sketch
is generated. Its function is to reliably covariate with the spatial
organization and dimensions of the body and its segments, in order to
spatially organize information coming from the body senses. This level
of body representation is partly independent from online inputs.



The body model thus seems to play an explanatory role. It remains
unclear, however, what kind of representation it consists in. On one
interpretation, it can be conceived as a kind of scenario in
Peacocke's (1992) sense. A scenario is a nonconceptual,
analogue, unit-free, spatial representation that uses a set of
labelled axes in relation to body parts. Peacocke describes scenarios
that depict the subject's environment, but arguably, one can
have a scenario that depicts the subject's body, with similar
properties. On another interpretation, it can be conceived as an
action-orientated representation (Brewer 1995; Bermudez 2005):




> 
> 
> The intrinsic spatial content of normal bodily awareness is given
> directly in terms of practical knowledge how to act in connection with
> the bodily locations involved. (Brewer 1995: 302)
> 
> 
> 


### 3.2 Taxonomies of body representations



Now one may ask whether we have only one model that depicts the whole
body or whether it is sufficient to have a collection of local models
(Alsmith forthcoming). Try, for instance, using a hand to touch your
foot whilst using the other to touch your face. To perform this task,
is it sufficient to have local body models that represent individual
body parts? Or do we also need a global body representation whose
function would be to structure these local representations?



One may further ask whether one can functionally defined different
types of body representations. One single body representation does not
seem to suffice to account for the variety of bodily disorders and for
the variety of aspects of bodily awareness. There needs to be more,
but how many? In 1911, Head and Holmes present the first taxonomy of
the representations of the body. In addition to what they call a body
image, which constitutes the conscious percept of the body, they
distinguish two types of unconscious representations, called body
schemata: one records every new posture or movement whereas the other
maps the surface of the body on which sensations are localized.
However, for a long time, the terms of body schema and body image had
been used interchangeably (see Schilder 1935, for instance), whereas
the fine-grained distinction between the two types of body schema had
almost completely disappeared. Nonetheless, since the eighties there
has been a renewal of interest for distinguishing various types of
body representation (O'Shaughnessy 1980; Paillard 1999;
Gallagher 1986), although there is little agreement, neither on the
way to individuate the distinct types of body representations, nor on
their precise number. Here is a sample of the
characteristics that have been used so far to distinguish them:


* Availability to consciousness (unconscious/conscious)
* Dynamics (short-term/long-term)
* Functional role (action/perception)
* Format (sensorimotor/visuo-spatial/linguistic/affective)
* Modality of input (proprioception/vision/interoception)
* Bodily information (enduring properties such as body metrics/body
posture/internal balance)
* Perspective (first-person/third-person)
* Direction of fit (mind-to-world/world-to-mind)



These distinctions give rise to different taxonomies (e.g., Schwoebel
& Coslett 2005; Sirigu et al. 1991; Paillard 1999; Dijkerman &
de Haan 2007; O'Shaughnessy 1980; Gallagher 1995), which
sometimes lead to opposite interpretations of the very same bodily
disorders. For instance, personal neglect (i.e., lack of exploration
of half of the body) has been interpreted as resulting from a deficit
of body schema (Coslett 1998), or from a deficit of body image
(Gallagher 1995). Furthermore, although most taxonomies rely on
neuropsychological dissociations, it does not seem likely that they
can account for all bodily disorders. Even three types of body
representation might not suffice to explain all the possible
dissociations. On the other hand, one may wish to avoid a
quasi-infinite list of body representations.



Even the definition of the body schema, which appears the less
controversial notion, often remains vague. The term 'body
schema' functions as a general term that groups together various
body representations intervening at different stages in motor control,
representing short-term or long-term body properties, used for
positive or negative affordances. It is commonly defined as the representation of the body
for action. But many states can contribute to action planning,
including some very high-level states. Imagine for instance that you
want to cut a cake into six equal slices. To do so, you can exploit
your mathematical knowledge that 360 degrees divided by 6 equals 60
degrees. This knowledge can guide your hand while splitting the cake.
Your ability to do maths can thus play a role in guiding your action,
but clearly, the body schema must be more intimately connected to
action. What makes the body schema so special? The type of information
that it represents? The way this information is represented? Or the
function of the representation? Furthermore, the distinction between
the body schema and the body image has become the stock in trade of
much recent work in cognitive neuroscience and philosophy. Yet little
is known about the interactions between these two types of body
representations (Gadsby 2018; Pitron,
Alsmith, & Vignemont 2018). In our everyday life the body we
perceive does not conflict with the body we act with. One needs to
account not only for dissociations in rare cases, but also for
convergence most of the time.


## 4. The sense of body ownership



According to Peacocke (2014, 2017), we must distinguish among three
degrees of self-representations:


* Degree 0: Mental states that do not represent anything as standing
in certain relations to the subject. For example, a proprioceptive
experience with nonconceptual content of the type [this leg is
bent].
* Degree 1: Mental states whose nonconceptual content represents the
subject as standing in relations to other objects and events. For
example, a proprioceptive experience with nonconceptual content of the
type [my leg is bent].
* Degree 2: Mental states that can use the conceptual first person.
For example, a proprioceptive judgment with conceptual content of the
type [my leg is bent].



Theories of the sense of bodily ownership try to answer the
following question: how does one go from degree 0 to degree 2, from a
proprioceptive experience with the nonconceptual content [this leg is
bent] to a proprioceptive judgment with the conceptual content [my leg
is bent]? These theories pursue two objectives. First, to avoid
positing new phenomenal properties unless necessary (Wu forthcoming).
Secondly, to account for empirical data. On the one hand, the rubber
hand illusion provides an experimental window in what is required for
one to experience a hand as one's own. On the other hand, one
needs to understand how it is possible for an individual *not*
to experience one's limb as one's own in disownership
syndromes, as in somatoparaphrenia (Romano & Maravita 2019), depersonalization disorder (Billon
2017), Cotard syndrome (Billon 2015, 2016), and xenomelia (Brugger et
al. 2013), as well as in chronic pain (Moseley et al. 2012) and
complex post-traumatic disorder (Ataria 2018). The interpretation of
these various results, however, is controversial (Alsmith 2015; Wu
forthcoming; Bradley forthcoming; Chadha 2018), and at most one can
only offer an inference to the best explanation.


### 4.1 The feeling of myness



The notion of myness, which can be defined as the *de se*
property of belonging to the subject, has recently attracted
increasing attention in the literature (Guillot 2017; Guillot &
Garcia-Carpintero forthcoming). The hypothesis then is that one
experiences one's body as one's own in virtue of having a
feeling of myness. Nonconceptual myness content can then provide
rational ground for conceptual myness content. The myness hypothesis,
however, is not without raising a number of controversies and most
recent views have rejected it (Alsmith 2015; Bermudez 2011;
Chadha 2018; 
Martin 1995; Vignemont 2020; Wu forthcoming). A first worry concerns
the origin of myness. Unless one posits myness as an irreducible
primitive phenomenal property (Billon 2017), the nonconceptual myness
content itself requires explanation. Another worry is that it does not
seem salient in our phenomenology. Chadha (2018) argues that by
default, the content of bodily experiences is not self-referential. On
her view, disownership syndromes do not result from the lack of
myness, but from an unusual feeling of the hand *not being one's
own*. One may also argue that the feeling of myness is not
compatible with a parsimonious conception of the admissible contents
of perception, according to which only low-level somatosensory
properties such as pressure, joint angle, and temperature can be
represented in the content of bodily experiences. Finally,
Bermudez (2011, 2015, 2018) appeals to Anscombe's
argument for knowledge without observation. He argues that one cannot
give a separately describable description of the feeling of myness,
which thus cannot constitute a legitimate ground for ownership
judgments.



Denying the existence of myness feelings, however, does not entail
denying the phenomenology of ownership: 



> 
> 
> ownership is phenomenologically salient ... when we experience
> our bodies we experience them as our own ... there is a
> phenomenology of ownership. (Bermudez 2015: 38) 
> 
> 
> 



In other terms, it makes a phenomenological difference when one is not
aware of one's body as one's own and when one is not. The
question then is how to best interpret this phenomenological
difference: in sensory terms (Wu forthcoming; Bermudez 2011;
Martin 1995; Dokic 2003), in cognitive terms (Alsmith 2015), in
agentive terms (Peacocke 2017), or in affective terms (Vignemont
2018).


### 4.2 The deflationary conception



According to what Bermudez (2011: 167) calls the deflationary
conception, 



> 
> 
> the sense of ownership consists, first, in certain facts about the
> phenomenology of bodily sensations and, second, in certain fairly
> obvious judgments about the body (which we can term judgments of
> ownership). 
> 
> 
> 



Likewise, Martin (1995: 278) states that the sense of ownership is not
an additional quality to the sensory qualities of bodily experiences
and that it is "somehow already inherent within them". For
instance, in the rubber hand illusion participants do not report only
ownership towards the rubber hand, but also referred tactile
sensations on the fake hand. One may then argue that experiencing the
rubber hand as one's own is nothing more than feeling sensations
in it (Wu forthcoming). One intuitive way to spell out the
deflationary conception is indeed in spatial terms: "when one
feels a bodily sensation to have a location there is no issue over
whose body it appears to belong to" (Martin 1992: 201). Martin
claims that the spatial phenomenology can account for the sense of
ownership because there is an identity between one's own body
and the body in which one locates bodily experiences. According to the
sole-object view that he defends, for an instance of bodily experience
to count as an instance of perception, it must indeed be an experience
of what is in fact the subject's actual body. However, one can
be aware of the boundaries of one's body without being aware of
the boundaries of one's body *qua* one's own (Dokic
2003; Serrahima forthcoming). A further problem for all
deflationary conceptions comes from dissociation between bodily
sensations and the sense of ownership. They indeed
predict that it is inconceivable for one to experience sensations in a
limb and fail to experience this limb as one's own (Martin 1995;
Dokic 2003). However, it has been found that patients with
disownership syndromes can still experience some bodily experiences
(e.g., Moro et al. 2004). The question then is whether this type of results can
invalidate the deflationary conception or not (Bradley
forthcoming).


### 4.3 The cognitive conception



Instead of appealing to the way one *perceives* one's
body, one can appeal to the way one *thinks* about one's
body in order to account for the sense of ownership: 



> 
> 
> A cognitive account of the sense of ownership holds that one
> experiences something as one's own only if one thinks of
> something as one's own. (Alsmith 2015: 881) 
> 
> 
> 



The cognitive conception does not preclude the existence of a
phenomenology of ownership, at least if one grants the possibility of
cognitive phenomenology (as in noetic feelings, for instance).



The question then is how to account for the fact that the sense of
ownership (or its lack) is cognitively impenetrable. Participants in
the rubber hand experiment are aware that the rubber hand is a fake
hand and they rarely endorse the belief that the rubber hand is their
own hand. Vice-versa: some patients know that their hand belongs to
them, and yet it still seems to them *as if* it did not, as
described by this patient: 'my eyes and my feelings don't
agree, and I must believe my feelings. I know they look like mine, but
I can feel they are not, and I can't believe my eyes'
(Nielsen 1938: 555). Cognitive impenetrability is classically taken as
the signature of experiential states. For instance, in the
Muller-Lyer illusion one cannot help but experience the two lines
as being different despite having the belief that they are actually of
the same size. However, there are attitudes other than feelings and
sensations that can be immune to the influence of beliefs (McDowell
2011). The question then is what kind of attitude: propositional
imagination (Alsmith 2015), agreement towards a proposition (Wu
forthcoming), perceptual seeming (Lyons 2011), or alief (Gendler
2008). Whatever attitude it may be, it will have to be not only
cognitive impenetrable, but also beyond the subject's control.
Subjects cannot decide at will to experience the rubber hand illusion.
In the case of disownership syndromes, it also seems that the attitude
they are in should be affectively-loaded. Patients indeed are greatly
distressed when they report that they do not feel their hand as their
own.


### 4.4 The agentive conception



Many theories appeal to the notion of action in relation to the sense
of ownership, and even more to the sense of disownership. The fact is
that disownership syndromes often involve some more or less extreme
motor impairment. Most somatoparaphrenic patients are paralyzed, and
those who are not suffer from the Anarchic hand sign (that is, they
cannot control their limb, which seems to have a will of its own).
Patients frequently complain about the uselessness of their
'alien' limb. There are then several ways the agentive
conception has been spelled out: in terms of body schema (Vignemont
2007), agentive feelings (B. Baier & Karnath 2008), or general
agentive ability (Peacocke 2017). The challenge that the various
versions face is that the sense of bodily ownership can be preserved
in patients who are paralyzed or who have lost the awareness of their
actions as their own. For example, anarchic patients report that they
have no control over their limbs but they still claim that their limbs
belong to them (Marchetti & Della Salla 1998). The rubber hand
illusion is also difficult to account for agentive conceptions. It has
been shown that there is no agentive contrast between synchronous and
asynchronous conditions, not only at the phenomenological level
(subjects report no agentive feelings toward the rubber hand, Longo et
al. 2008), but also at the sensorimotor level (the way they perform
their movements is not altered by the illusion, Kammers et al. 2009).
Peacocke's (2017) agency-involving account may then seem the
most promising because it appeals to the notion of action at a
relatively high level of generality. On his view (Peacocke 2017: 293),
a subject can experience that this is her own hand if and only if:


1. there is a range of action notions *A* for which the creature
must be capable of being in mental states... with the content
*c* is *A*-ing where the state... is produced by the
initiation of an *A*-ing by the reference of c;
2. there is a range of notions *F* of bodily properties, spatial
properties, and past tense properties *F* such that the creature
is capable of being in mental states... with the content *c*
is *F*; where in these attributions, *c* is *F* is
accepted (in central basic cases) if and only if this body is *F*
is also accepted.



Paralyzed patients still know what it is like to act and that should
be sufficient for them to still feel their inert limbs as their own
(Peacocke 2019). One might also say that in the rubber hand illusion,
participants know what it is like to act with a hand in general
although they do not feel they could act with this specific rubber
hand. However, this account puts so few constraints on what it
takes to experience one's body as one's own, that one may
wonder how it is even possible to lose the sense of bodily ownership.
What is the agency-involving difference between the paralyzed patients
who deny ownership and those who do not? 


### 4.5 The affective conception



These last 20 years have seen an explosion of experimental work on
interoception. Recent accounts of interoception have highlighted its
role for self- awareness, positing it at the core of what is sometimes
called the "sentient self" (Craig 2003), the "proto-
self" (Damasio 1999), the "embodied self" (Seth
2013), or the "material me" (Tsakiris 2017). Even
Descartes in his *Meditations on First Philosophy* take
interoceptive feelings to be the key for our unique relationship with
our body: 



> 
> 
> Nature likewise teaches me by these sensations of pain, hunger,
> thirst, etc., that I am not only lodged in my body as a pilot in a
> vessel. (Descartes 1641 [2016] *Meditation VI*, p. 56) 
> 
> 
> 



However, even if interoception can ground some notion of the self, it
is not clear that it is specifically involved in the sense of bodily
ownership. Imagine a creature that only receives interoceptive
signals. It receives information about its body, and its body only.
But there is a difference between self-specificity (information
exclusively about the body that happens to be one's own) and
self-reference (awareness of the body *qua* one's own).
The problem is that on the basis of interoception only, there is no
need to discriminate the inside from the outside since the body is
only an inside. It is so fixated on its own body that it can dispense
with representing whose body is hungry or thirsty. The fact is that
one usually says "I am thirsty", without any reference to
bodily ownership, let alone to the body.



There is, however, another way to spell out the affective conception
without appealing to interoception. Instead it appeals to the notion
of affective significance (Vignemont 2018). On what is called the Bodyguard hypothesis, there is a
specific affective phenomenology that goes over and above the sensory
phenomenology of bodily experiences. It expresses the unique value of
the body for the self, a value that is evolutionarily rooted. In
brief, survival involves preservation of one's body. The sense
of ownership then individuates the one body that matters to the
subject for self-preservation more than anything else. In line with
this view, it has been found that participants who report ownership
for the rubber hand display an increase of arousal when the rubber
hand is under threat (Ehrsson et al. 2007). Vice-versa, patients with
somatoparaphrenia show no increase in arousal when they see the hand
that they felt as alien under threat (Romano et al. 2014).



One may object that evolutionary significance is only a consequence of
the fact of bodily ownership: this body matters because it is mine.
Consequently, affective phenomenology should be just the consequence
of the sense of bodily ownership: I feel that this body matters
because I am aware that it is mine. However, one may reply that what
happens to the body that has this significance happens to me. Why is
it so? One possibility is that it is because I am my body or more
simply because we evolved in a world such that for the self to
survive, its body must survive. Hence, for my body to have such
significance is for it to be the body to protect for the
organism's evolutionary needs. Biology here provides an
independent ground to the notion of significance. The impact on what
happens on this body for oneself gives immediate ground for labeling
it as one's own. Hence, one is entitled to judge that this is
one's own body when one feels that this body matters in this
special way, because under normal circumstances the body that matters
in such a way is one's own body.


## 5. Conclusion



Bodily awareness reveals a new rich territory for philosophical
exploration in its own right, but it also provides a new approach to
general issues of perception, action, self and space. Empirical
research on body representations, bodily sensations, bodily illusions,
and self-awareness has grown exponentially. A comprehensive
understanding of bodily awareness will likely require taking on board
its insights.