A “zombie,” in the philosophical sense of the term, is a creature physically and behaviorally identical to a human being but devoid of any sort of mental life. That’s somewhat imprecise, in part because the notion of a zombie could also cover creatures physically and behaviorally identical to some non-human type of animal but devoid of whatever mental properties that non-human animal has. But we’ll mostly stick to human beings for purposes of this post. Another way in which the characterization given is imprecise is that there are several aspects of the mind philosophers have traditionally regarded as especially problematic. Jerry Fodor identifies three: consciousness, intentionality, and rationality. And the distinction between them entails a distinction between different types of zombie.
The kind of zombie usually discussed in recent philosophy of mind is a creature physically and behaviorally identical to a human being but devoid of the qualia characteristic of everyday conscious experience. Call this a qualia zombie. If you kick a qualia zombie in the shins he will scream as if in pain; if a flashbulb goes off in his face he will complain about the resulting afterimage; if you ask him whether he is conscious or instead just a zombie he will answer that of course he is not a zombie and that the whole idea is absurd. In every way he will act just like a normal human being would and if you examined his body you would find that both externally and internally it is identical to that of a normal human being. But if you had the metaphysical equipment with which to peer inside his conscious experience, you would find there is none at all -- no actual feeling of pain associated with his scream, no actual afterimage associated with his complaint, no conscious awareness of any sort associated even with his vigorous protest against the suggestion that he is a zombie.
The point of this sort of thought experiment is to show that there is a gap between the material facts about our nature, on the one hand, and the facts about conscious experience on the other. This is philosophically significant both because it suggests that materialism is false and because it suggests that there is a problem about knowing other minds. If the material facts about us could be the same but without the presence of consciousness, then consciousness (so the argument goes) must not be material. If we could know all the material and behavioral facts about a person but still not know from that alone whether or not he is a zombie, then there is a problem of explaining how we know that he really isconscious and not a zombie.
This sort of zombie argument is the flip side of Descartes’ argument to the effect that you could exist even if your body did not. Descartes imagines a scenario (his “evil genius” thought experiment) in which your conscious experiences are as they are now, but there is no material world at all, and thus in which you have no brain or body at all. Conscious thought could exist in the absence of matter; therefore (Descartes concludes) conscious thought is not material. The zombie scenario is one in which matterexists in just the way it does in the actual world but without any consciousness. Once again we seem to have the result that consciousness and matter are distinct. The divorce between them is absolute. (Given the provenance of zombies in the everyday sense, Steely Dan fans might call it a “Haitian divorce.”)
Are qualia zombies really possible? I don’t think so, but before we get to that let’s consider the other sorts. A second kind of zombie would be one devoid of intentionality, i.e. the directedness or “aboutness” of at least some mental states. Your belief that it is sunny outside is about or directed at the state of affairs of its being sunny; your perception of a dog in front of you is aboutor directed at the dog; and so forth. The intentionality of mental states is like the meaning that written or spoken words have, except that where their meaning is derivative -- there is nothing in the physical properties of ink marks or sound waves that gives them any meaning, so that meaning must be conventionally assigned to the marks or sounds by language users -- the intentionality of mental states is somehow “built in.”
Consider a creature physically and behaviorally identical to a normal human being or non-human animal but devoid of intentionality. Call this an intentional zombie. An intentional zombie might utter and write the same sounds and shapes a normal human being would, might give what seemed to be the same gestures, and so forth, but none of this would actually involve the expression of any meanings, since the zombie would entirely lack any meaning, intentionality, or aboutness of any sort. It would react to objects in its surrounding environment in just the way a normal human being or other animal would, but there would be nothing in it that counted as a representation of these objects. For instance, an intentional zombie “dog” might start wagging its tail in the presence of a bowl of Alpo and run over to the bowl and start eating, but not because there was anything in it that counted as a perceptual state that was about or directed at the dog food. (Donald Davidson’s “swampman” example is essentially concerned with the question of whether an intentional zombie is possible.)
A third sort of zombie is one we might call a cognitive zombie. Rationality essentially involves the ability to form concepts, to put them together into propositions, and to reason from one proposition to another in a logical way. Obviously this involves intentionality, but it goes beyond that. Anything with rationality has intentionality, but not everything with intentionality has rationality. A dog has intentionality insofar as its perceptual experience of the dog food points to or is directed atthe dog food. But it does not have a concept of dog food, or any other concept for that matter. Rationality -- which, again, essentially involves the use of concepts -- goes hand in hand with language.
Now a cognitive zombie would be a creature physically and behaviorally identical with a human being, but devoid of rationality -- that is to say, devoid of concepts and thus devoid of anything like the grasp of propositions or the ability to reason from one proposition to another. It would speak and write in such a way that it seemed to be expressing thoughts and arguments, but there would not be any true cognition underlying this behavior. It would be mere mimicry.
If zombies of any sort are possible at all, then presumably something could be a cognitive zombie without being an intentional zombie or a qualia zombie. It might lack true concepts (even if it acts like it has them) but still possess intentionality of the sort non-human animals possess, as well as qualia. In the same way, something could arguably be an intentional zombie without being a qualia zombie (unless we go along with the view that all consciousness is intentional in at least a thin sense). An intentional zombie would ipso factobe a cognitive zombie, though. Less clear is whether a qualia zombie need be an intentional zombie. Plants, after all, are not conscious but do have something comparable to intentionality insofar as they are “directed at” certain ends (sinking roots, growing toward the light, etc.). So perhaps a qualia zombie could still have at least rudimentary intentionality corresponding to such low level activities (though it would be incapable of any sort of intentionality essentially associated with qualitative conscious states). Also unclear is whether a qualia zombie would be a cognitive zombie. Angels, qua disembodies intellects, would certainly lack the qualia associated with corporeality. However, there is clearly a sense in which they would be conscious. So, if a qualia zombie is something devoid merely of the qualia we associate with corporeality, then being a qualia zombie would not entail being a cognitive zombie. But if being a qualia zombie entails being devoid of any sort of consciousness whatsoever, then being a qualia zombie would presumably entail being a cognitive zombie.
We might call a creature that exhibits the entire package of zombie options -- something physically and behaviorally identical to us but devoid of qualia, intentionality, cognition, and indeed mentality of any sort whatsoever -- The Compleat Zombie. Now available as a stocking stuffer for that special someone.
Or it would be if zombies were really possible. But I think they are not. Start with qualia zombies. The very idea is, as I have noted before, an artifact of the modern post-Galileo, post-Cartesian “mathematicized” conception of matter taken for granted by Cartesians and materialists alike. If you definematter so that color, sound, heat, cold, etc. as common sense understands them are not really in matter at all but only in our conscious experience of it -- so that color as an objective feature of the world is redefined in terms of surface reflectance properties, sound in terms of compression waves, and so forth -- then naturally color, sound, heat, cold, etc. as common sense understands them are not going to be identifiable with or explicable in terms of “material” features of the world. This is the reason way materialism will always be afflicted by objections of the sort raised by Jackson, Nagel, Chalmers, et al., and given the conception of matter the materialist takes for granted these objections are unanswerable.
However, we Aristotelians would reject this conception of matter. To speak of matter merely in terms of those among its properties which can be described in the language of mathematical physics is to speak of an abstraction. What physics tells us about matter really is there in matter, but it is only part of what is there. Now for the Aristotelian, what matter is essentially is the potency for the reception of form, and there are as many kinds of material substance as there are kinds of substantial form. Given the nature of water or stone, the sort of material substance that results from a composition of prime matter and the substantial form of water or stone is naturally going to be devoid of qualia. But given the nature of a dog (say) it is metaphysically impossible for prime matter to be informed by the substantial form of a dog while lacking qualia. Physics gives you, in effect, a lowest common denominator description of material substances. But material substances are simply not all reducible to this lowest common denominator, nor is the description physics gives us of the “micro-level” in any way metaphysically privileged. A dog is not less real than the particles that make it up. Indeed, it is more real, since given Aristotelian hylemorphism, the particles exist only virtually rather than actually in the dog. The same thing can be said of fish and birds, gold and led, you name it. None of these things is any less real or less fundamental to physical reality than the micro-level is.
Obviously this is all very sketchy and very controversial. See Oderberg’s Real Essentialism or my forthcoming Scholastic Metaphysics for the long story. The point here is not to defend or even give much in the way of an exposition of the Aristotelian account of material substance, but merely to note that given its radical anti-reductionism, the very notion of a qualia zombie cannot get off the ground. The same thing is true of the notion of an intentional zombie. For the Aristotelian account of material substances includes the notion of irreducible intrinsic teleology or finality. It is of the nature of the phosphorus in the head of a match to point to or be directed at the generation of flame and heat; it is of the nature of an acorn to point to or be directed at growing into an oak; and so forth. In the same way, given what a dog is, it necessarily going to have states which point to or are directed at things like food, mating opportunities, predators, etc. Hence there is, given the Aristotelian conception of material substance, no such thing as a creature materially and behaviorally identical to a dog yet lacking any “directedness” of any sort.
It is no accident that the Aristotelian tradition regards sensation and imagination as entirely corporeal and in no way supportive of dualism. What contemporary philosophers call qualia and intentionality (or at least a rudimentary sort of intentionality that involves mere directedness without conceptual content) are, for the Aristotelian, simply ordinary corporeal features of certain kinds of ordinary material substances. This only sounds odd if you assume that a material substance is “really” “nothing but” something going on at the micro-level -- particles in motion, say. For naturally (the Aristotelian would agree) it is hard to see how the feel of pain, the way red looks, the way heat feels, etc. can be reduced to or explained in terms of particles in motion, the firing of neurons, or the like. But that is a perverse way of thinking of material substances. To describe a dog in terms of the particles that make up its body or the firing of certain neurons in its nervous system is like describing a painting at the level of the splotches of color scattered about on a canvas. It is to abstract out from a whole certain parts which are metaphysically less fundamental than the whole is.
More interesting is the question of whether cognitivezombies are possible on an Aristotelian view. For the Aristotelian does regard rationalityas at least partially non-corporeal. Following James Ross, I have defended the claim that formal thinking is immaterial because it has a determinacy of content that purely material systems cannot have. (I had reason to defend this argument recently against objections raised by Robert Oerter.) Does this sort of argument entail that cognitive zombies are possible? In particular, does it entail that a creature could be physically and behaviorally identical to a normal human being but (since cognitive activity has an immaterial aspect) nevertheless devoid of any concepts or the rational activity that presupposes concepts? (Compare Oerter’s “Hilda” example.)
I think it does not. Ross’s argument holds, and need hold, only that no set of material facts entails any determinate content; the argument does not and need not hold that the material facts could be just as they are without any content at all. Consider the following analogy: You might know that Δ is a symbol without knowing exactly what it is a symbol of. A particular triangle? Triangles in general? A dunce cap or slice of pizza? The material facts about Δ alone won’t tell you, even if you know on independent grounds that it is a symbol of something or other. Similarly, Ross’s argument does not require that we cannot know from the physical and behavioral facts alone whether a person has thoughts with someconceptual content or other. It requires only that the physical and behavioral facts alone do not metaphysically determine what, specifically that content is.
In that case, though, Ross’s argument would establish that there is an immaterial aspect of thought -- and it is significant that he speaks in his original paperspecifically of “immaterial aspects of thought” -- without thereby entailing that a creature could be physically and behaviorally identical to a human being without having anythought content whatsoever. It would refute materialism without entailing the possibility of cognitive zombies or opening up a problem of other minds. (Whether Ross’s argument somehow indirectlyentails the possibility of a cognitive zombie, or whether any other Scholastic argument for the immateriality of the intellect does so, are questions I will leave for another time.)
