DESPITE ITS GREAT DIVERSITY of forms, life has brought forth only a few basic modes of being during its natural history on Earth. Unicellular autopoiesis, as we have seen, is the minimal organization of life. Multicellularity, the cooperative linking together of multiple cellular individuals to form a body, is the basis for the other modes of being. If we regard bacteria and protists as forming multicellular colonies rather than distinct individuals, then we can say that there are basically three ways of being a multicellular organism, classified on the basis of how subsistence is derived or nourishment procured: the plant mode, in which subsistence takes the form of feeding on light; the fungi mode, in which food is extracted or absorbed from a surrounding environment of other organic beings; and the animal mode, in which nourishment must be actively searched for and pursued. Animal life is thus marked by a distinctive sensorimotor way of being in the world. This sensorimotor way of being, in its full extent, comprises locomotion and perception, emotion and feeling, and a sense of agency and self—in a word, sentience.
The subject matter of Part III is consciousness, beginning with bodily sentience. Earlier in this book I described sentience as the feeling of being alive. Being sentient means being able to feel the presence of one’s body and the world. Sentience is grounded on the autopoietic identity and sense-making of living beings, but in addition it implies a feeling of self and world. How to account for the emergence and presence of sentience in the natural world is one of the outstanding problems of the sciences of mind today.
To prepare the way for our investigation of consciousness in the remaining chapters of this book, I begin by examining some prevalent philosophical assumptions about consciousness and biological life. The point of this examination is to show that the dualistic separation of consciousness and life makes it impossible to understand consciousness in its basic form of bodily sentience. According to the enactive approach, there is a deep continuity of life and mind, including conscious mentality, and the philosophy of mind needs to be rooted in a phenomenological philosophy of the living body.
Many philosophers of mind today believe that a profound difference exists between consciousness and mere biological life. On the one hand, consciousness, or more precisely, so-called phenomenal consciousness, is thought to be an internal, subjective, qualitative, and intrinsic property of certain mental states. Life, on the other hand, is thought to be an external, objective, structural, and functional property of certain physical systems. Given this way of thinking, the attempt to understand consciousness and its place in nature generates a special problem, the so-called hard problem of consciousness (Chalmers 1996, 2002; Nagel 1974): how is consciousness, as experienced from the inside by an individual conscious being, related to the natural life of that being, as observed and understood from the outside? In Thomas Nagel’s words:
For if the facts of experience—facts about what it is like for the experiencing organism—are accessible only from one point of view [the subjective point of view], then it is a mystery how the true character of experiences could be revealed in the physical operation of that organism . . . The problem is unique. If mental processes are physical processes, then there is something it is like, intrinsically, to undergo certain physical processes. What it is for such a thing to be the case remains a mystery. (1979, pp. 172, 175)
The problem is that physical accounts explain the structure and function of a system as characterized from the outside, but a conscious state is defined by its subjective character as experienced from the inside. Given this difference, physical accounts of structure and function seem insufficient to explain consciousness. In other words, there seems be an explanatory gap between physical structures and functions and consciousness (Levine 1983). Thus it is a mystery how conscious experiences could be physical processes.
According to this way of thinking, there is no equivalent hard problem about how biological life is related to physical structure and function. Thus David Chalmers writes:
When it comes to the problem of life … it is just obvious that what needs explaining is structure and function: How does a living system self-organize? How does it adapt to its environment? How does it reproduce? Even the vitalists recognized this central point: their driving question was always “How could a mere physical system perform these complex functions?”, not “Why are these functions accompanied by life?” . . . There is no distinct “hard problem” of life, and there never was one, even for vitalists. (Chalmers 1997, p. 5)
The thought proposed here is that although physical accounts of structure and function are conceptually and logically sufficient to account for living processes, consciousness is different. Conscious experience, though associated with various cognitive functions, such as perceiving things around one and reporting or expressing one’s state of mind, seems resistant to functional analysis. Many philosophers believe that the physical structures and functions that make up a conscious being are not conceptually and logically sufficient to account for the subjective character of its experience. These philosophers think they can conceive of a system that is physically identical to a conscious being, but that either has systematically different sorts of experiences from that conscious being (an “invert”) or lacks conscious experience altogether (a “zombie”). According to this way of thinking, whatever continuity exists between life and mind holds only for the functional properties of the mind and not for consciousness. There is no deep continuity of life and consciousness but rather a radical break between them. Given a complete and precise account of the physical structure and function of a living, conscious being, nothing about its conscious experience logically or conceptually follows. As Chalmers writes: “For a phenomenon such as life . . . the physical facts imply that certain functions will be performed, and the performance of those functions is all we need to explain in order to explain life. But no such answer will suffice for consciousness” (1996, pp. 106–107).
This line of thought is questionable. It is well known that sentience is deeply involved with life-regulation processes of complex organisms (Damasio 1999; Panksepp 1998b; Parvizi and Damasio 2001). We therefore ought to be suspicious of any apparently intractable dichotomy between consciousness and life. In other words, we ought to be suspicious of the concepts of consciousness and life that lie behind this formulation of the hard problem.
A historical remark may be useful at this point. Chalmers asserts that even the vitalists recognized that the concept of life is a functional concept. Hence, he says, there was no hard problem about life for vitalism, only a problem about understanding how a physical system could carry out various vital functions (metabolism, growth, repair, reproduction, and so on). This interpretation, however, seems incorrect. Some vitalists did indeed encounter a hard problem about life (Garrett, in press). Like those philosophers who think it conceivable that a physical duplicate of a conscious being could lack consciousness altogether, these vitalists thought it conceivable that organized, moving bodies, functionally indistinguishable from organisms, could lack “vitality.” These vitalists asked, why are these organized movements accompanied by life? This reasoning strikes us as empty because we no longer accept the vitalist concepts of matter and life. Our concept of matter is no longer that of inanimate, minute, extended bodies governed by mechanical laws of motion, and our concept of life is no longer that of a special property of vitality. It seems reasonable to suppose that the concepts of consciousness and life that figure in the standard formulation of the hard problem are similarly inadequate.
My point in drawing this analogy is not to imply that consciousness is functionally definable in the same way materialists think that life is functionally definable. On the contrary, as I argued in Chapter 6, there is an inwardness to life that standard materialist accounts fail to recognize. My point is rather that to make headway on the problem of consciousness we need to go beyond the dualistic concepts of consciousness and life in standard formulations of the hard problem. In particular, we need to go beyond the idea that life is simply an “external” phenomenon in the usual materialist sense. Contrary to both dualism and materialism, life or living being is already beyond the gap between “internal” and “external.” A purely external or outside view of structure and function is inadequate for life. A living being is not sheer exteriority (partes extra partes) but instead embodies a kind of interiority, that of its own immanent purposiveness. This interiority, as we have seen, comprises the self-production of an inside that specifies an outside to which that inside is constitutively and normatively related.
To borrow Heidegger’s terminology, living being has a kind of “in-being,” and in-being is an existential structure that cannot be adequately described in the language of external structure and function (Heidegger 1985, pp. 165–166). This kind of in-being, that of autopoietic interiority, is not a matter of material boundedness. As Heidegger points out, a living being is “in” its world in a sense completely different from that of water being in a glass (ibid.). The interiority of life is the interiority of selfhood and sense-making, which is a precursor to the interiority of consciousness. A living being enacts a milieu marked by significance and valence. Exteriority is surmounted by an internal relation of meaning and normativity between the two poles of organism and milieu. There is thus an inwardness to life that escapes a purely external conception. This inwardness underlies the deep continuity of life and mind, and is the context in which the emergence of consciousness must be understood.
The problem with the dualistic concepts of consciousness and life in standard formulations of the hard problem is that they exclude each other by construction. Hence there is no way to close the gap between them. To reduce conscious experience to external structure and function would be to make consciousness disappear (materialism); to reduce external structure and function to internal consciousness would be to make external things disappear (idealism); and to inject some third ingredient between the two is a desperate effort to bridge an unbridgeable chasm. The hard problem is thus not so much hard as impossible. The problem of making comprehensible the relation of mind and body cannot be solved as long as consciousness and life are conceptualized in such a way that they intrinsically exclude one another. For this reason, it is crucial to realize that this chasm is a philosophical construction built on sedimented and problematic ways of thinking going back to Descartes. We need to look more closely at this Cartesian legacy, for it remains a powerful force in many contemporary treatments of the problem of consciousness.
Descartes is mainly responsible for conceptualizing consciousness as inner experience accessible only to first-person reflection, and life as external and mechanical structure and function. Before Descartes, in the Aristotelian tradition, life and mind belonged together under the heading of soul (psyche). For Aristotle, soul is not an immaterial substance, but in the broadest sense it is the capacity of the organism to be active in various ways. It thus encompasses whatever capacities or abilities belong to life, including cognitive or mental ones. In a striking image, Aristotle says that the soul is to the body as vision is to the eye: “if the eye were a living creature, its soul would be its sight” (De Anima II, I, 412b 19; see Mensch 1996, p. 175). In this conception, the soul is logically inseparable from the body. Precisely in the way it is inconsistent to suppose that the act of seeing can exist without the functioning of the eye, or that the eye can function properly without the act of seeing, so it is inconsistent to suppose that the soul—the vital capacities of the body—can exist without a living body or that a living body can exist without a soul. For Aristotle, exactly as seeing is the goal or purpose of the eye, so the soul is the totality of goals something must embody to be alive. Soul and body are thus two sides of the one single process of living. There are different kinds of soul, however, depending on the goals life can or must embody. These ends are nourishment and growth (the nutritive or vegetative soul); feeling and sensation (the sensitive soul); self-motion and self-direction (the volitional soul); and reason and the use of symbols (the rational or intellectual soul).1
With the rise of mechanistic natural philosophy in the sixteenth century, the Aristotelian view of natural phenomena as goal-directed was rejected. According to the mechanistic worldview, there are no goals or purposes inherent in the natural world; nature operates only according to the mechanical laws that govern matter in motion. To be alive is not to strive to realize a certain telos but to be a particular configuration of matter governed by mechanical principles. The Aristotelian notion of soul came to be seen as a fiction that did not apply to anything in the natural world. Instead, the soul was now equated with the rational mind, which transcends nature and whose essence is conscious thought.
Descartes played a key role in effecting this separation of mind and nature, consciousness and life. He rejected both the traditional connection between being conscious and being alive, as well as the traditional separation of living things and mechanisms (Matthews 1991). On the one hand, consciousness is a property of the immaterial mind or soul, and therefore the conscious mind per se is not alive. On the other hand, being alive is a property of the human body, which is simply a machine, and therefore the living body per se is not conscious. Consciousness and life have different natures, and no matter how closely united they are within a human person, they can nevertheless exist apart (as indeed supposedly happens after death, according to Descartes’s Catholicism).
Descartes’s separation of consciousness and life involved a new way of thinking about consciousness in relation to sense experience (Matthews 1991). According to the traditional Aristotelian conception, sensation and perception logically require a body. That is, the statement (1) S senses or perceives something, entails (2) S has a bodily organ of sensation or perception; and therefore (3) S has a body (or is a body). Descartes, however, in the “Second Meditation” of his Meditations on First Philosophy, proposes a new meaning for “sense-experience” (sentire), in which the entailment from sense-experience to the existence of one’s body no longer holds. He writes that he can doubt whether he has a body (it is possible he is deceived), and therefore his body might not belong to his proper essence. He cannot doubt, however, that he is consciously thinking, and therefore he must be essentially a thinking thing. But what exactly is a thinking thing? It is, he states, “A thing that doubts, understands, affirms, denies, is willing, is unwilling, and also imagines and has sense perceptions” (Descartes 1986, p. 19). Yet how can a mere thinking thing, that is, a thinking thing that is supposed to have no body, also imagine and have sense perceptions, which apparently require a body? Descartes’s answer is that even if none of the objects of his imagination is real, the power of imagination nevertheless belongs to his thinking. Similarly, even if none of the things he senses is real, it certainly seems to him that he senses them: “I certainly seem to see, to hear, and to be warmed. This cannot be false; what is called ‘having a sensory perception’ is strictly just this, and in this restricted sense of the term it is simply thinking [or consciousness]” (ibid.).
The upshot of this restricted sense of sense-perception, according to Gareth Matthews’s explanation, is “a new concept, consciousness, which includes thinking plus the ‘inner part’ (so to speak) of sensation and perception” (Matthews 1991, p. 68). Put another way, to arrive at the proper conception of consciousness, “We must (so to speak) ‘peel off’ from seeing, hearing, tasting, etc., the seeming to see, to hear, to taste, etc., which is such that one cannot do that and also doubt that one is doing it” (ibid). Such “seemings” provide the intrinsic “phenomenal contents” (as they are called today) of perception, and they do not logically entail the existence of one’s body (or any other thing of nature for that matter).
Unlike the Aristotelian concept of soul, Descartes’s new concept of consciousness was radically divorced from the concept of life. Yet it also had a first-person, phenomenological orientation missing from the concept of soul. Aristotle recognized the unity of soul and life only from an impersonal standpoint. He never discussed the body from an inward point of view, as one’s own body (Patocka 1998, pp. 8–11). Descartes, however, established his separation of consciousness and life on the basis of a first-person starting point. Beginning from his own self-awareness, he asked what must indubitably be the case given his own experience. Sometimes this first-person impulse led him to reflect on bodily experience, in particular when he had to account for the experiential unity of mind and body in his own case. Thus, in a famous passage in the “Sixth Meditation,” Descartes rejected the metaphor of the soul as a pilot of its ship:
There is nothing my nature teaches me more vividly than that I have a body, and that when I feel pain there is something wrong with the body, and that when I am hungry or thirsty the body needs food and drink and so on. So I should not doubt that there is some truth in this.
Nature also teaches me, by these sensations of pain, hunger, thirst, and so on, that I am not merely present in my body as a sailor in a ship [the French version reads: as a pilot in his ship], but that I am very closely joined and, as it were, intermingled with it, so that I and the body form a unit. If this were not so, I, who am nothing but a thinking thing, would not feel pain when the body was hurt, but would receive the damage purely by the intellect, just as a sailor perceives by sight if anything in his ship is broken. (Descartes 1986, p. 56)
Yet the undeniable fact that I and my body form a unit is precisely what Descartes’s philosophy is unable to explain.The body for Descartes is simply a mechanical thing, and any inwardness or sentience that apparently belongs to its vital functioning lies on the other side of a metaphysical divide, in the realm of immaterial consciousness. But if the conscious mind and the living body are thus completely different, then the fact that they form a distinct unity in each individual human being is incomprehensible. In particular, the fact that my mind is united to my body is entirely accidental or arbitrary, for as a matter of metaphysical principle my mind could just as easily be united to some other body. There is thus no way for Descartes to make good on his advance over Aristotle in recognizing the personal character of the living body (see Patocka 1998, pp. 9–20).
After Descartes there was a current of European thought that confronted the Cartesian separation of mind and body, consciousness and life, by reflecting once more on bodily experience (see Merleau-Ponty 2001). A prime example is the French philosopher Marie-Francois-Pierre Maine de Biran (1766–1824), who from his earliest texts in 1794 to the last pages of his Journal never ceased to wonder at what he called the “feeling of existence” (le sentiment de l’existence). Maine de Biran did not contest the disembodied Cartesian thinking ego in the name of some kind of sentimentalism. Instead he tried to grasp the very source of the personal “I,” which, he held, is to be found in the bodily experience of exercising effort in movement. Jan Patocka, the noted Czech phenomenologist, describes Maine de Biran’s insight this way:
I have a primordial awareness of effort, of having certain possibilities, for instance, of moving my hand. The meaning of effort, of my purposive manipulating of my body, stems from myself. From this effort I know immediately that the movement stems from me as from an autonomous center . . . We are primordially an active I, exercising effort.
Effort has its bounds: something resists it. It is not boundless energy, it is an efficacity of the body, a bodily effectiveness. Here it becomes evident that the I is possible only as corporeal—the I is a willing, striving I and, consequently, a corporeal one. This includes various modes—freshness, fatigue, exhaustion, etc. . . . An I is possible only in a biological organism. A biological organism becomes a real person in the moment I can do something on my own (i.e., move). (Patocka 1998, p. 25)
Maine de Biran’s “feeling of existence” is another way of describing sentience, the feeling of being alive. This notion points away from the disembodied Cartesian concept of consciousness and back to the primordial experience of exerting effort and being affected, that is, to consciousness as bodily sentience.
Attention to sentience can also help us to see the limitations of another aspect of Descartes’s legacy—the penchant for “zombies” among many philosophers of mind today (Chalmers 1996, pp. 94–99; Moody 1994). A zombie is a fictional entity that has exactly the same physical structure, functional mechanisms, and behavior as a conscious human being, but has no conscious experience whatsoever. If such an entity is logically or conceptually possible, if it is genuinely conceivable without contradiction or some other kind of incoherence, then (so the argument goes) materialist analyses of consciousness in terms of physical structure and function cannot be correct.
This argument is deeply Cartesian in form. Descartes argued in his Meditations on First Philosophy that the mind is essentially conscious thought, the body is essentially extension or the occupation of space, and it is perfectly conceivable that conscious thought can exist apart from extension. Although Descartes concluded that the mind and the body are not identical, his argument can be turned around, as Nagel pointed out in one of the earliest versions of the modern zombie argument:
The existence of the body without the mind is just as conceivable as the existence of the mind without the body. That is, I can conceive of my body doing precisely what it is doing now, inside and out, with complete physical causation of its behavior (including typically self-conscious behavior), but without any of the mental states which I am now experiencing, or any others for that matter. If that is really conceivable, then the mental states must be distinct from the body’s physical states. (Nagel 1980, p. 205)2
With regard to these sorts of arguments, Nagel went on to observe the following: “The real issue is whether one can know that one has conceived such a thing . . . What must be shown, to defeat the Cartesian argument, is that when we try to conceive of our minds without our bodies, or vice versa, we do not succeed in doing that, but instead do something else, which we mistake for it” (1980, p. 205).
The Cartesian argument in its zombie form provides an extreme case of the radical conceptual divorce between consciousness and life. Your hypothetical zombie twin is physically and biologically identical to you; it is a complete duplicate of the biological organism that you are. It is therefore alive exactly as you are, with regard to every structural, functional, and behavioral detail. Nevertheless, it does not feel alive in the slightest; it is not sentient.
This thought seems incomprehensible. We are asked to imagine a living being, a human organism, whose bodily life is identical with respect to its physical structure and function to that of a conscious human being, but that has no bodily sentience, no subjective experience of its bodily existence and environment. In phenomenological language, we are asked to imagine a physical living body (a Körper) that is physically and behaviorally identical to a conscious being, but that is not a lived body (a Leib). It is hardly clear that this scenario is conceivable or imaginable strictly as described. The scenario requires that a physical counterpart (a molecule-for-molecule duplicate) of a given conscious subject’s actual-world body have a bodily life indistinguishable from that of the conscious subject in every respect except for having no subjective experience whatsoever of its own body (Hanna and Thompson 2003).
Yet many of the perceptual and motor abilities of one’s physical living body (the body as Körper) evidently depend on that body’s being a subjectively lived body (a Leib). Without proprioceptive and kinesthetic experience, for example, many kinds of normal perception and motor action cannot happen. The zombie scenario requires the assumption that bodily experience is not necessary for or in any way constitutive of the relevant behavior, that exactly the same behavior is possible without bodily sentience. This assumption is quite strong and needs to be argued for independently. There is little reason to believe it. Although one can make a conceptual distinction between bodily experience from the inside and bodily functioning from the outside, it hardly follows that the latter could exist without the former.
It is worth elaborating this line of thought in relation to phenomenological analyses of perception. One of the central themes of Husserl’s analyses of perception is that every visual or tactile perception is accompanied by, and functionally linked to, the sensing of one’s bodily movements (hand movements, eye movements, head movements, whole-body movements, and so on) (Husserl 1997). Every aspect or profile of an object given to tactile or visual perception is not simply correlated to a kinesthetic experience of one’s body but is functionally tied to that experience. When one touches the computer keys, for example, the keys are given in conjunction with a sensing of one’s finger movements; when one watches a bird in flight, the bird is given in conjunction with a sensing of one’s head and eye movements. Husserl argues at length that perceptual continuity—the continuity of the object through a changing manifold of appearances—depends on this linkage of kinesthesis and perception. As he states, it is through one’s movement and bodily self-experience in movement that an object presents itself as a unified series of appearances. In other words, bodily self-experience in the form of kinesthesis is a constitutive condition of ordinary perception.
Behind this analysis is the idea that in order to perceive an object from a certain perspective—to take its appearance or profile from that perspective as an appearance of an objective thing in space—one needs to be aware, tacitly or prereflectively, of other coexisting but absent profiles of the object. These absent profiles stand in a certain relation to the present one: they can become present if one carries out certain movements. In other words, they are correlated to one’s kinesthetic system of possible bodily movements and positions. If one moves this way, then that aspect of the object becomes visible; if one moves that way, then this aspect becomes visible. In Husserl’s terminology, perception is “kinesthetically motivated.”
For simplicity, we can take the case of a motionless object. If the kinesthetic experience (K1) remains constant throughout a given time interval, then the perceptual appearance (A1) remains constant too. If the kinesthetic experience changes (K1 becomes K2), then the perceptual appearance changes too (A1 becomes A2). There is thus a functional interdependency between the kinesthetic experiences and the perceptual ones. A given appearance (A1) is not always correlated with the same kinesthetic experience (e.g., K1), but it must be correlated with some kinesthetic experience or other. For this reason, perception is bound up with kinesthetic and proprioceptive experience.
The result is that prereflective bodily experience, the tacit experience of one’s body, is constitutive of perception. How, then, can we make sense of the idea of a completely unconscious being, a being with no experience whatsoever of its own body, whose (functionally defined) perceptual abilities are exactly those of its (physically identical) conscious counterpart? For this scenario to make sense it must be conceivable that a being having normal human perceptual abilities could have no kinesthetic experience of its body and no prereflective experience of itself as an embodied agent. But if the phenomenological analysis is right, then bodily experience is constitutive of the perceptual function of individuating continuous objects in space through a manifold of sensory appearances. So any being that was capable of the same perceptual function would need to have an experience of its own body and hence could not be a zombie.
This line of reasoning challenges confidence in the imaginability of the zombie scenario but does not demonstrate that the scenario is inconceivable. My aim, however, is not to refute the belief in the logical possibility of zombies, as it were head-on. One does not need to demonstrate the logical impossibility of zombies by deriving a formal contradiction from the supposition to call into question this supposition’s philosophical value (pace Chalmers 1996, p. 96). One need only reveal the problematic assumptions on which it rests—that exactly the same behavior can happen in the presence and absence of sentience, and that sentience is a strictly internal and phenomenal occurrence, whereas behavior is entirely a matter of external structure and function. Given these problematic assumptions, philosophers should not be allowed to get away with simply asserting that the zombie scenario seems conceivable to them. They must describe the scenario in sufficient detail so that it is intelligible given the apparent inseparability of a conscious subject’s physical living body (its Körper) and its lived body (its Leib).
This demand requires more than what zombie aficionados provide. Jaegwon Kim, for example, simply asserts that zombies seem conceivable “without much difficulty” (Kim 1998, pp. 101–102). And Chalmers writes:
I confess that the logical possibility of zombies seems equally obvious to me [as that of a mile-high unicycle]. A zombie is just something physically identical to me, but which has no conscious experience—all is dark inside. While this is probably empirically impossible, it certainly seems that a coherent situation is described; I can discern no contradiction in the description. In some ways an assertion of this logical possibility comes down to a brute intuition, but no more so than with the unicycle. Almost everybody, it seems to me, is capable of conceiving of this possibility. (Chalmers 1996, p. 96)
I disagree. It hardly seems true that, when asked to imagine the scenario in sufficient detail, almost everyone can conceive of this possibility or that they can do so without much difficulty (see Cottrell 1999; Dennett 1995b). What does seem true is that the scenario will seem conceivable to anybody who is under the sway of the Cartesian concept of consciousness and who has not thought carefully about what the scenario, strictly described, actually demands of one’s imagination, in particular with regard to the phenomenology of bodily experience. The putative logical possibility of zombies is therefore not like the logical possibility of a mile-high unicycle. The latter supposition involves simply an imagined variation on the physical size and structural proportions of a thing, but the former supposition involves an intellectual extrapolation to the limit of a deeply problematic way of thinking about consciousness and bodily life.
The Cartesian concept of consciousness also leads to an extreme skepticism about other conscious minds. How could one ever tell the difference between a zombie and a conscious subject? If “zombiehood” is possible, then it is possible (conceptually or logically, if not empirically) that your spouse, child, closest friend, or lover is a zombie without you or anyone else knowing. Such a supposition expresses at its most extreme the Cartesian problem of other minds.3 But it gets even worse. As Guven Güzeldere observes: “Zombiehood brings with it not only the problem of other minds, and thus third-person [and second-person] skepticism, but first-person skepticism as well. If you, the reader of these lines, suddenly turned into a zombie, no one would notice any difference, and in a significant sense of ‘noticing’ [the external, functional sense], neither would you” (Güzeldere 1997, p. 43). One problem with this kind of skepticism is that our understanding of what it is to be a conscious subject is intersubjectively constituted through empathy. (By “empathy” I mean the sensorimotor and affective coupling of our lived bodies as well as our mutual imaginative exchange of cognitive and emotional perspectives.) I will return to this idea in Chapter 13.
The moral of this discussion is that instead of starting from the concepts of mind and body in standard formulations of the hard problem we need to take our start from the lived body. To close this chapter I would like to reformulate the problem of the explanatory gap by taking life and the body as our starting point.
If on the one hand mental processes are bodily processes, then there is something it is like, intrinsically, to undergo certain bodily processes. On the other hand, if there belongs to certain bodily processes something it is like to undergo them, then those bodily processes are experiences. As Nagel (1974) puts it, they have a “subjective character,” without which they would cease to be experiences. They are feelings in the broad sense that William James had in mind when he used the word “feeling” “to designate all states of consciousness merely as such” (1981, p. 185) and that Antonio Damasio has revived by describing feelings as “bearing witness to life within our minds” (Damasio 2003, p. 140). The problem of what it is for mental processes to be also bodily processes is thus in large part the problem of what it is for subjectivity and feeling to be a bodily phenomenon.
In this formulation of the hard problem, I have substituted the term body for physical.4 Body connotes life, a living organism, and is richer in meaning than physical in the Cartesian sense. Drawing on this richness can help us to refine the terms of the explanatory gap.
Phenomenologists distinguish between two ways the body can be disclosed or constituted in experience—as a material thing (Körper) and as a living subject of experience or lived body (Leib). We need to refine this distinction, however, for at least two reasons. First, we need to guard against the danger of reifying a phenomenological distinction between two ways our body can be disclosed into an ontological duality. The body can be disclosed as a physical body and as a lived body, but this does not imply that there are two bodies or that the body has two mutually irreducible, metaphysical properties or aspects.5 Second, even this distinction between two modes of bodily presence, correlated with two ways of experiencing the body, is inadequate, because it does not convey the diversity of ways the body can be disclosed in our experience.
Husserl had to avail himself of a variety of terms for the spectrum of differentiated ways the body can be disclosed, from an objective physical body to a subjective life-flow, with various notions of the body as living or lived in between (Depraz 2001a, pp. 2–111).6 Subsequent phenomenologists have elaborated, enriched, and refined these analyses. As we will see in Chapter 13, there is also a complex intersubjective structure of experience, linking how one’s own body is disclosed to oneself and how it is disclosed to another (as well as how another’s body is disclosed to oneself). For these reasons, “body” has to be taken as naming an open region of investigation and analysis, not a fixed ontological reference point in some abstract metaphysical scheme (like “physical” and “mental” in Cartesian dualist or materialist metaphysics).
I have argued that the standard formulation of the hard problem is embedded in the Cartesian framework of the “mental” versus the “physical,” and that this framework should be given up in favor of an approach centered on the notion of life or living being. Although the explanatory gap does not go away when we adopt this approach, it does take on a different character. The guiding issue is no longer the contrived one of whether a subjectivist concept of consciousness can be derived from an objectivist concept of the body. Rather, the guiding issue is to understand the emergence of living subjectivity from living being, where living being is understood as already possessed of an interiority that escapes the objectivist picture of nature. It is this issue of emergence that we need to address, not the Cartesian version of the hard problem.
To sharpen this issue, we need to refine the phenomenological distinction between the physical body and the lived body. In addition to this basic distinction, we can distinguish between the structural morphology of the physical body and its living and lived dynamics (Cole, Depraz, and Gallagher 2000). The morphology comprises the bodily structures of limbs, organs, regulatory systems, brain structures, and so on, whereas the dynamics comprises the lived flow of life, that is, the flow of intentional movement and lived sensations (interoceptive, exteroceptive, and proprioceptive). There does not seem to be any explanatory gap in the transition from seeing the body as a physical object to seeing it in its structural morphology as a living body. But there does seem to be a gap or discontinuity in the movement from seeing the body as a living body to seeing it as a lived body, as a locus of feeling and intentional activity—in short as sentient. What exactly is the nature of this gap?
Two points are important here. First, the gap is no longer between two radically different ontologies (mental and physical), but between two types within one typology of embodiment. Second, the gap is no longer absolute because in order to formulate it we need to make common reference to life or living being. For these reasons, and to highlight the contrast with the Cartesian formulation of the hard problem, we could call this explanatory gap the body-body problem (Hanna and Thompson 2003).
The difference between the body-body problem and the Cartesian hard problem is philosophically nontrivial. In the hard problem, the explanatory gap is absolute because there is no common factor between the mental and the physical (and there can be none given how they are defined). Hence the main options are to accept the gap as a brute ontological fact (dualism), to close the gap by reduction (materialism or idealism), or to bridge the gap by introducing some third and speculative “extra ingredient” (for which there is no scientific evidence or motivation). These options make no sense for the body-body problem. In finding our way to this problem, we have had to jettison the traditional Cartesian vocabulary of mental versus physical entities and properties. The lived body is the living body; it is a dynamic condition of the living body. We could say that our lived body is a performance of our living body, something our body enacts in living. An important philosophical task is to show how there can be an account of the lived body that integrates biology and phenomenology, and so goes “beyond the gap” (Bruzina 2004; Roy et al. 1999). The scientific task is to understand how the organizational and dynamic processes of a living body can become constitutive of a subjective point of view, so that there is something it is like to be that body. For the enactive approach, this task takes the form of trying to understand a lived body as a special kind of autonomous system, one whose sense-making brings forth, enacts, or constitutes a phenomenal world.
Before ending this chapter, I would like to compare the approach to consciousness and life I have been exploring with John Searle’s “biological naturalism” (Searle 1992, 2004). Searle also rejects the traditional categories of mental and physical. He writes: “If we are going to keep this terminology at all, we need an expanded notion of the physical to allow for its intrinsic, subjective mental component” (2004, p. 116). For Searle, conscious states are biological processes that are intrinsically qualitative, subjective, and first-personal. They have a subjective or first-person ontology, which means that they exist only insofar as they are experienced by a conscious animal or human subject. Conscious states are constitutively first-personal, and therefore are ontologically irreducible to brain processes described neurophysiologically, which are constitutively third-personal. At the same time, consciousness is causally reducible to the brain because it is entirely caused by lower level neurobiological processes and is realized in higher level or systemic brain activity.
I share Searle’s view that consciousness is a subjective biological process and that, so described, it is irreducible to brain processes described neurophysiologically in the third person. But there are also differences between our views.
I have argued that we already need an expanded notion of the physical to account for life and to prepare the way for any further expansion needed to account for consciousness. Life is not physical in the standard materialist sense of purely external structure and function. Life realizes a kind of interiority, the interiority of selfhood and sense-making. We accordingly need an expanded notion of the physical to account for the organism or living being. Furthermore, I find compelling Robert Rosen’s view that such an expanded, biological notion of the physical would be generic or typical in its application to nature rather than a special case (Rosen 1991, 2000). Although organisms are statistically rare in the class of physical systems, it does not follow that they are special or nongeneric in that class (Rosen 1991, pp. 13, 37; 2000, p. 27). Most of physics has been developed for thermodynamically closed rather than open systems, and especially not for autopoietic systems or living systems generally, which are precisely those systems for which individuality and interiority are applicable concepts. It is the closed systems that are organizationally special or nongeneric, not the open ones. Rosen makes an analogy to rational and irrational numbers in arithmetic: “We have … a predilection for rational numbers, a predilection that gives them weight out of all proportion to their actual abundance. Yet in every mathematical sense, it is the rational numbers that are rare and very special indeed. Why should it not be the case with physics and biology? Why could it not be that the ‘universals’ of physics are only so on a small and special (if inordinately prominent) class of material systems, a class to which organisms are too general to belong? What if physics is the particular, and biology the general, instead of the other way around?” (1991, p. 13).
I also differ from Searle in my assessment of the irreducibility of consciousness. Searle observes that, in standard cases of scientific reduction, a given type of phenomenon, such as heat or color, gets redefined in terms of its underlying microphysical causes (molecular kinetic energy or light reflectances), such that its subjective appearance (felt heat or perceived color) is excluded from its definition.7 Thus, causal reduction of the macroscopic causal properties to the microstructural ones, and redefinition of the phenomenon in terms of its microstructure, are supposed to support ontological reduction of the phenomenon to its microstructural constituents.
This pattern of reduction depends on the appearance/reality distinction: the phenomenon is supposed to be reducible because it can be redefined in terms of the underlying reality and not the appearance. In the case of consciousness, however, we cannot make this appearance/reality distinction because “consciousness consists in the appearances themselves” (Searle 1992, p. 122).8 Hence “the point of the reduction would be lost if we tried to carve off the appearance and simply defined consciousness in terms of the underlying physical reality” (ibid). Searle, however, thinks the irreducibility of consciousness is trivial, for it is simply “a trivial consequence of the pragmatics of our definitional practices” (ibid.). We define consciousness in terms of the subjective appearances, not the underlying physical reality, with the result that “the reductions . . . that leave out the epistemic bases, the appearances, cannot work for the epistemic bases themselves” (ibid.).
By contrast, I think the irreducibility of consciousness is not trivial and indicates that consciousness has a transcendental status in addition to an empirical one. Consciousness, considered as epistemic base, is not equivalent to the perceptual appearances, which pertain to empirical objects as given to our consciousness. Consciousness as epistemic base is equivalent to the experiential acts by which those objects are disclosed to us. From a phenomenological perspective, objects are disclosed in the ways they are—as complex structured manifolds of appearance—thanks to certain essential formal laws under which experience necessarily operates so as to disclose a meaningful world. Consciousness considered in this way is a condition of possibility for there being any appearances at all. To understand consciousness this way is to understand it transcendentally and not merely empirically. Thus I take the irreducibility of the epistemic bases themselves to point toward the need for a transcendental perspective on consciousness (see also Rowlands 2003).9
The last difference I want to mention concerns Searle’s view that consciousness is causally reducible entirely to the brain. This view provides a way to see consciousness as a causally efficacious biological process. Consciousness in Searle’s view is a higher level or global state of the brain that is causally relevant to the organism’s behavior and subsequent neural activity. This neurobiological conjecture coincides with several neurodynamical proposals about consciousness (see Cosmelli, Lachaux, and Thompson 2007; and Chapters 3, 11, and 12 of the present volume). Nevertheless, the view that consciousness is entirely causally reducible to the brain may be biologically premature. We simply do not yet know whether the brain alone is the minimal causal basis for consciousness or whether this basis also includes features of the brain-body interface or brain-body-environment interface.
Consider the philosophical thought experiment of the brain in a vat. Your brain is removed from your body and is artificially maintained in a chemical vat where it receives exactly the same stimulation to all its neuronal terminals that it normally receives as you go about your life. Would you (or your brain) notice any difference? Would you not have qualitatively identical subjective experience? Philosophers have used this scenario to motivate many ideas, one of which is that the brain (or some subsystem of the brain), and nothing outside the brain, is the minimally sufficient condition for consciousness or subjective experience. Yet this claim does not follow from the brain-in-a-vat scenario. Rather, what follows is that, whatever is the minimally sufficient condition for consciousness, this condition has been successfully realized by the vat setup. For all we know, this condition necessarily includes as a proper part something outside the brain, provided in this case by the vat.10
Notice that the vat setup would have to be capable of (1) keeping the brain alive and up and running, (2) duplicating all exogenous stimulation, and (3) compensating in exactly the right way for all endogenous (and self-organizing) activity. Such a setup would almost certainly have to duplicate many of the chemical, biomechanical, and sensorimotor properties of the body, probably even the body’s sensorimotor coupling with the world. In other words, the null hypothesis is that any vat that meets the requirements of this scenario will be a surrogate body. Hence the brain-in-a-vat thought experiment does not establish either that consciousness is entirely causally reducible to the brain or that the minimally sufficient condition for consciousness resides exclusively within the brain. Perhaps bodily processes belong to the minimally sufficient condition for consciousness and the “vat” would have to be a surrogate body.11
One might object that we already know that direct electrical stimulation to the cortex can produce various sorts of conscious experiences. Is this fact not good reason to think that, given appropriate background conditions in the rest of the brain and body, there must be some neural substrate that is minimally sufficient for the instantiation or realization of consciousness?
This proposal, however, depends on empirical considerations that are far from settled. We simply do not yet know the minimal biological requirements for the instantiation or realization of consciousness. It is one thing for neural activity to be the minimal sufficient condition for the instantiation of a fleeting, episodic moment of phenomenal consciousness. It is quite another thing for neural activity to be the minimal sufficient condition for the instantiation of consciousness in the sense of coherent and temporally extended intentional experience of the world. As the above considerations about the brain-in-a-vat scenario suggest, such consciousness might require nothing less than a living body engaged with the world.
Even if the minimally sufficient condition for consciousness is indeed the brain, it does not follow that we are nothing over and above our brains. Consider these statements by Searle: “The brain is all we have for the purpose of representing the world to ourselves and everything we can use must be inside the brain. Each of our beliefs must be possible for a being who is a brain in a vat because each of us is precisely a brain in a vat; the vat is the skull and the ‘messages’ coming in are coming in by way of impacts on the nervous system” (Searle 1983, p. 230). Yet the brain is not all we have, and not everything we can use for the purpose of representing the world is inside our brain. We have our body as well as resources in the environment, and it is far from obvious that any bodily process or environmental resource used in representing the world needs to be represented inside the brain. Each of us is precisely not a brain in a vat but rather a bodily subject. The body is not a vat, and any so-called vat that could duplicate or stand in for the body would most likely have to be a surrogate body. The brain is an organ, not an organism, and it is the organism, animal, or person that has conscious access to the world. As conscious subjects we are not brains in cranial vats; we are neurally enlivened beings in the world.
Although for every subjective and phenomenal change in one’s conscious experience there is presumably a corresponding change in one’s brain, it remains an open question to what extent these changes are explicable independent of the sensorimotor and environmental contexts of brain activity.12 The hypothesis of the enactive approach is that the relation between experience and the brain will remain opaque unless these contexts figure explicitly in our accounts. This issue is central to the next chapter.