Tuesday, April 15, 2008

Joining the Herd by Bleating About Zombies

The philosophy blogosphere has been abuzz with zombie talk recently (Siris helpfully compiles some of the recent discussions here; and here are some I especially like), so I’ve finally decided to conform and throw a couple of thoughts out there, though I can’t promise they’ll be coherent. For those who don’t know, zombies are imaginary beings exactly like us in every physical respect, but lacking our phenomenal consciousness. And the zombie argument is supposed to go from the alleged conceivability of such beings to evidence that the phenomenal cannot be reduced to the physical. My own stance is roughly that zombie thought experiments are silly, as well as seriously problematic. They are problematic, on my view, not simply because (like too many thought experiments) they are set up to pump our intuitions about imaginary cases about which we don’t really have clear intuitions, but also because, by giving the illusion of clarity, they are designed to convince us that we really do have intuitions, reliable ones, about things we in principle cannot have reliable intuitions about. So here are a couple of thoughts.

I. Zombie arguments seem to me to presume that we have intuitions about what counts as physical. Atoms, apparently, do. The experience of redness or pain, on the other hand, does not. But what is the physical? Presumably, the physical domain is just the domain of that which can be studied by the physical sciences. If we grant that, however, then it turns out that our intuitions about what counts as physical are entirely dependent on which sciences we consider physical sciences, and what our understanding is of what those sciences do. In other words, the intuition that the domain of the physical cannot accommodate phenomenal properties seems to rest on the idea that the physical world is composed of little particles bouncing around in accordance with laws. Since physics has moved a bit beyond Newton, however, I wonder whether those intuitions really make sense.

Importantly: the counter-intuitiveness of quantum mechanics is frequently mentioned. At the very very micro level, physical entities don’t behave the way we would expect them to. So we know that our intuitions about how physical things behave are just wrong, according to what the physical sciences tell us. And it isn’t like there are no unresolved questions. Given this, it isn’t clear that we can or should trust any intuitions about whether or not the phenomenal is or is not reducible to the physical, because we cannot trust our intuitions about the physical. And this thought seems to me to undermine a basic presupposition of the zombie argument: that zombies are conceivable in some more robust way than square circles. Quite possibly, zombies seem conceivable to us just because we have no idea what it is we are conceiving. And the zombie argument, by pushing the possibility of this conceivability, makes its point by making us further confused about what it is we are conceiving.

II. Even if we do grant that zombies are possible—that the physical as we now understand it (again, assuming that we do understand it)—does not include phenomenal properties, this is hardly an argument against reductionism as such. That is: what it gives us is an argument that phenomenal properties (if they exist) are irreducible to the current subject matter of the physical sciences. But this point can just as easily be turned around. The point of the physical sciences is to provide confirmable theories with predictive power that apply to whatever sorts of things we encounter in reality. If our current physical theories cannot do this for phenomenal properties, that can only be taken to show that our current physical theories are still a far way off from giving us absolute knowledge. But we already know that, and it doesn’t give us grounds for a priori arguments that they cannot go beyond their present boundaries.

I once heard Chomsky make a remark that went something like this: At the end of the 19th century, scientists were convinced that chemistry was entirely irreducible to physics. Today, it is more or less common sense that this view is false, because a paradigm shift in the physical sciences made the move from physics to chemistry possible. Why, then, should we think that the same cannot be done for phenomenal properties and physics? There is one answer, which has to do with distinguishing between the third-personal methods of science and the first-personal features of qualia. I will save discussion of that thought for my next post.

III. As I understand it, the phenomenal realist’s claim is that there are two sets of laws in our world. First, there are laws that govern the behavior of physical entities. Second, there are laws that govern the relation of physical and phenomenal entities. The zombie world looks the same as ours from the outside because the first set of laws is the same there. But they don’t have the second set of laws. Implied is a metaphysical view according to which the universe is composed of some substances, like elementary particles, together with a bunch of natural laws. But I am not sure that is right. Speaking of substances and laws implies that both are contingent. One might have the exact same laws, but completely different substances. Alternatively, one could have exactly the same substances but different laws. This may be useful as a shorthand way of speaking about reality, but I doubt it makes much sense. Instead, it seems more likely that substances and laws are co-constitutive. Here is what I mean:

How do we know anything about fundamental particles? Well, we know what they are like because of the effects they have on other things: other particles, our instruments, and our brains. And it is not clear that there is anything else to these particles than their effects, or dispositions to bring about certain effects, with a marked regularity. My point is not the idealist one, that since we can only know anything about reality through our perception of it, there is nothing to reality aside from our perceptions. Rather, the point is that we have no grounds for attributing any properties to substances other than causal ones, and these causal properties are nomological. We know what a particle is like because of the law-like effects it produces, and we have no warrant to say anything about it other than that it produces such effects. (That the laws are sometimes probabilistic ones does not change this picture.) And the reverse is true as well. Our knowledge of natural laws depends on the actions of particles (or macro-phenomena composed of particles). Again, I am not trying to argue that laws are nothing apart from the behavior of substances. My point is that we have no warrant to speak of laws as literally something apart from substance. From the standpoint of the sciences, it seems to me, laws just are the formulae according to which substances behave, whereas substances just are what behaves in accordance with laws.

And this is why it seems strange to me to think that the very same substances could exist in two universes with radically different sets of laws. If qualia stand in nomological relations to matter, we have three options. (1) Qualia are different substances, and the second set of laws is missing from zombie world because there is nothing for physical substances to stand in relation to. (2) Something about the physical entities in zombie world really is different, since the entities don’t have the same effects. (3) There are no nomological relations between physical substance and qualia. I doubt anyone would accept the third option these days; the parallel clock argument has had its day. The first option is also not very tempting—once we start talking about two heterogeneous substances, we run into all sorts of problems about how nomological relations between them could be possible at all. So that leaves option two: zombie world is not composed of the same physical substances as our world. And this, of course, is what almost everyone (aside from the few hardcore zombie-philes) has been saying.

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