Sunday, April 24, 2011

Troubles with the zombie argument in philosophy of mind

First of all it is important to keep in mind my initial disambiguation of intentional states and phenomenal states. It is already established that intentional states, since they are supervenient on physical states, can only be categorized operationally. Phenomenal states, as the friend of qualia has characterized them, cannot be categorized operationally (since they are beyond the reach of language). Of course an android could distinguish color surfaces without recourse to qualitative experience. We don’t think that there is “something that it’s like” for welder-directing robots in automobile factories to locate the seams with lasers. So when we are told that we can conceive of zombies it must be that we are meant to be conceiving of beings that are physically identical to humans but have no conscious experience. That functional descriptions can supervene on multiple physical descriptions has no bearing on the ontological status of qualia at all. I will make two arguments that are variations on the larger set of arguments presented here. First that the zombie counterfactual assumes something that it purports to show, and second that the zombie argument is an example of skepticism and is vulnerable to some counter-skeptical arguments.

The zombie counterfactual turns out to be question-begging: the friend of qualia has included qualia-body dualism as one of the premises. The claim is that we can conceive of beings that are physically identical to humans but that do not have immaterial phenomenal mental properties, unlike, presumably, the actual humans. To see this, try the same thought experiment only with the initial assumption (the most reasonable one, on the principle of parsimony) that qualitative experience will ultimately be explicable in wholly physical terms (that is, assume materialism as the default metaphysical position). The thought experiment now looks strikingly different.

Now (assuming materialism to be axiomatic, instead of dualism) the zombie argument is not question-begging: our initial assumption is that both the “blueness” of the surface of the plastic chair and the “blueness” of the phenomenal experience of the surface of the plastic chair are qualities had by virtue of the physical properties of the perceived chair and the perceiving body respectively. Now try this assertion on for size: “I can conceive of the plastic chair as having the identical physical properties that it now has (including its light-absorbing and –reflecting properties) but not having any color at all.” This is definitely inconceivable. When I try to conceive of an object with no color I for one try to imagine that the objects are transparent - I’m not sure if that counts as an object that has no color but it’s the best I can do. I cannot conceive of a physical object that is physically identical to an object that is colored but that has no color. This is just an application of the argument that to the extent that what I know, I know through “experience,” it makes no sense to draw a distinction between the phenomenal and the physical.

A second line of argument is suggested by the way Wittgenstein’s linguistic arguments can be deployed against skepticism. “Philosophical skepticism” is any argument to the effect that you don’t know something that you’re certain that you do know. Modern skepticism is closely connected to rationalism: Descartes thought that logical proof was the paradigm of “knowledge,” and it turned out, perhaps unsurprisingly, that by that standard we know very little. “The Problem of Other Minds” is a skeptical argument: you’re certain that other people have experiences and thoughts like yours but it seems that you can’t prove it. The Zombie problem is a variant on the problem of other minds: can’t you just see that other people are conscious? What would it be to doubt this? If the Zombie argument is an example of skepticism then we should be able to extend Wittgenstein’s treatment of skepticism to the Zombie argument.

A famous back-and-forth between Wittgenstein and G. E. Moore is good for illuminating this. In his essay “Proof of an External World” (1939) and elsewhere Moore is arguing in much the same philosophical spirit as Wittgenstein (they both think that skepticism is a pseudo-problem with roots in a faulty understanding of language), but Wittgenstein’s remarks on Moore’s arguments (included in On Certainty) make a crucial difference clear. Moore, presaging the “Ordinary Language” movement, wanted to show that “common sense,” by which he meant, roughly, ordinary talking and thinking about our physical selves in our physical world, was better defended with reasons than the speculative bases of skepticism and the “idealism” (really a kind of phenomenalism) still powerful in English philosophy at the beginning of the 20th century. Moore thought that our perceptions of our own bodies in the environment were instances – paradigmatic instances - of knowledge, not belief. Holding up his hand he would say, “I know I have a hand.” From the plain fact that I know I have a hand there arises similar knowledge of, ultimately, the external world: the keyboard is a reason for (believing in) the hand, the hand is a reason for the keyboard; the desk is a reason for them both and so on.

Wittgenstein’s response to skepticism is altogether different. Drawing on his premise that language must have operational criteria for determining appropriate conditions of use, Wittgenstein challenges the skeptic’s use of the verb “to know.” Take an ordinary (non-philosophical) instance of using that verb: “Do you know where your keys are?” The question makes sense because one might know or might not know, and “knowing” can be defined operationally: one can put one’s hands on one’s keys or one cannot. The question, “Do you know that the external world exists?” has no criterion for use: nothing could count as demonstrating that the external world either does or does not exist. That is, we neither “know” nor do we “not know” that the external world exists. The word “knowledge” has no place here. Where Moore proposed a kind of normative epistemology that would, if accepted, constitute an argument for the existence of the external world, Wittgenstein denies that there could be any argument one way or the other: Moore has taken the bait and tried to play a game that can’t be played.

Here we can see Wittgenstein’s “soft” arguments about language and his “hard” argument called “solipsism” come together. It is important also to see that Wittgenstein is much closer to Hume than Moore is. Hume (like Berkeley) stresses that the assertion that the external world “exists” is just as untenable as the assertion that it might not. Both sides of the disjunction are nonsense, if either side is.

The problem of other minds is exposed to the same treatment as a pseudo-problem. PI 246:

In what sense are my sensations private? – Well, only I can know whether I am really in pain; another person can only surmise it. – In one way this is wrong, and in another nonsense. If we are using the word “to know” as it is normally used (and how else are we to use it?), then other people very often know when I am in pain. – Yes, but all the same not with the certainty with which I know it myself! – It can’t be said of me at all (except perhaps as a joke) that I know I am in pain. What is it supposed to mean – except perhaps that I am in pain?
Other people cannot be said to learn of my sensations only from my behavior, - for I cannot be said to learn of them. I have them.
The truth is: it makes sense to say about other people that they doubt whether I am in pain; but not to say it about myself.

If I say “I know he’s conscious” and you challenge me by excluding all operational criteria from counting as justification for my claim, all you will do is change the ordinary meaning of the (public) word “conscious.” But then I’ll just have to start using another word for the same purpose, because what I have to say will remain exactly the same. PI 403:

If I were to reserve the word “pain” solely for what I had hitherto called “my pain”, and others “L. W.’s pain”, I should do other people no injustice, so long as a notation were provided in which the loss of the word “pain” in other connexions were somehow supplied. Other people would still be pitied, treated by doctors and so on. It would, of course, be no objection to this mode of expression to say: “But look here, other people have just the same as you!”
But what should I gain from this new kind of account? Nothing. But after all neither does the solipsist want any practical advantage when he advances his view!

As for “consciousness,” its meaning will now be anything you care to stipulate – in other words nothing - since you’ve stipulated that one can’t hear, see, smell, taste or touch anything that could even possibly indicate its presence: much like the word “god.” Thinking about the semantics of the word “god” brings us back to the first argument about the question-begging nature of the Zombie counterfactual. If the claim is that an operational theory of mind such as functionalism, specifically, has a problem with qualia, it must at least be a tacit assumption that there could be some non-operational theory of mind (a traditional one? a popular one? a philosophical one?) that does not: one that actually incorporates information about “what it’s like” into psychological descriptions and explanations. But there is no theory of mind like that, and if the arguments rehearsed in this chapter are correct there cannot be one.

Even after all of this, though, Nagel’s point still stands: there is “something that it’s like” for me to have a qualitative experience, and mine might very well be different from a Martian’s, or a dog’s or even yours. Although language cannot express these “qualia,” much less produce coherent claims that they are “properties” distinct from physical properties, our progress here has not been wholly destructive. I am now in a position to say a few things, after all, about the metaphysics of phenomenal experience.


  1. Interesting analysis, but I think that you're not being fair to the zombie argument. The argument is usually phrased in terms of 2-dimensional semantics, which eliminates the appearance of question-begging.

    It's not clear when you say that consciousness can be wholly explicable in material terms whether you think that this it will be explicable a priori or whether it will happen to be a matter of natural law that qualia are caused by certain physical properties.

    The Zombie argument was really designed to defeat an a posteriori physicalism that claims that dualism could have been true, but just happens not to be. Under this understanding there is no barrier to conceiving of a zombie world (in that conceivability implies only that a proposition is not ruled out a priori). So the argument in this case doesn't involve question-begging because the a posteriori (or type-B) physicalist admits the conceivability of zombies, but denies their possibility.

    If you mean to say that physicalism should be a priori in the sense that qualia should be logically derivable from the true physical laws, then the full apparatus of the zombie argument is not required. The a priori (type-A) physicalist is making a strong metaphysical claim that is not compatible with a very intuitive thought experiment involving zombies. Because type-A physicalists believe that physics logically entails qualia, they don't have access to a parsimony argument either, since parsimony only tells us which of two logically possible alternative to believe in. We wouldn't use arguments about parsimony in mathematics, for instance, so we can't use them to appeal to claims of logical entailment in philosophy either.

    At this point the a priori physicalist has to make a substantive argument about why zombies are not actually conceivable, even though they seem to be coherent.

    As far as zombie intuitions being susceptible to Wittgenstein's language arguments, I guess you're right. I haven't been convinced by those arguments particularly, but I think that the conceivability of zombies is the same as our inability to disprove solipsism a priori. If you think that Wittgenstein has disproved solipsism a priori, then you're right that zombies should also be disproved. I'm just not sure that most people accept those Wittgensteinian arguments against skepticism.

  2. Anonymous, You are obviously well-versed in the professional discussion of this topic. It would be nice to know who you are and to have an e-mail if you were interested in more discussion. (I can't figure out how to show the comments on the blog).
    My view is that qualia do not exist. I find support for this view in Hume, Wittgenstein, and some Buddhist philosophy. That is, qualitative experience of the world is not something that can be said to exist in the experienced world. Experience of properties has no properties.
    I am excited, not daunted, when someone remarks that "most people don't accept those arguments."

  3. I can imagine a fitness landscape which selects for being a zombie (by making mental representation punitively costly) within the terms of this gedanken. If our own ability to discriminate zombies from us is not being selected for- indeed, if it is adaptive for us not to notice zombie 'tells'- then, for all we know, we may indeed be living in such a world. Moran (1992) shows how competition between kin might drive genetic polymorphism.

    More generally, against stochastic fitness landscapes, anything adaptive (as opposed to wholly impossible and imaginary)is going to be radically polymorphic in a sense I am tempted to call reverse mereologically- i.e. it acts like 'a hopeful monster' towards some new and larger whole- in which case, I cant see how arguments that appeal to a 'FIST' can be considered persuasive in our Zeitgeist.

    On the other hand, rigor of this sort has much to recommend itself for the project of reconstructing Classical Sanskrit Buddhist logic- at least in its influence on the Nyaya School.