Sunday, April 02, 2006

Zombies Revisited: Correction and Clarification

A while back I wrote about philosophers’ zombies, and I’ve had a bit of feedback to the effect that I misunderstood some of the positions I outlined, and drew the wrong conclusions from what was said. I realise now the mistakes I made, and want to briefly clear them up.

The most significant errors are in my discussion of David Chalmers, and his views on ‘functional’ and ‘biological’ zombies (see my earlier post for what I meant by these). Richard Chappell, in a comment on the previous post, says “You've got Chalmers completely wrong”. I think this is a little strong, but I certainly was wrong on some points. I claimed that Chalmers believes in the logical possibility of biological zombies and their nomological impossibility, which is correct (David Chalmers, personal communication), but I mistakenly suggested that he takes functional zombies to be nomologically possible, when in fact he doesn’t (although Chalmers argues that functional zombies, like biological zombies, are logically possible). I don’t think my discussion of Chalmers was very clear, and I misinterpreted what he was getting at in some of his responses to Sue Blackmore’s question in Conversations On Consciousness.

This was partly a failure to identify the proper focus of the discussion (which to be fair is not made explicit in the interviews with Blackmore – the distinction between logical and nomological is not made, for instance). I was suspicious of the power of mere logical possibility to tell us anything about the actual world we live in, so I was focusing on what was nomologically possible. But, according to Chalmers, the most interesting question for philosophers with regard to zombies is what is logically possible. I’m still unclear on why logical possibility is so interesting. It seems that all sorts of possibility are logically coherent, but their conceivability doesn’t seem to provide a reason to explain the presence or absence of these imagined possibilities in our world, which is the one we’re interested in explaining. But I’m open to being corrected on this.

Philosopher Gualtiero Piccinini has also suggested to me that Block’s reading of Chalmers is correct, and that I was therefore in error to suggest that Block has misread Chalmers, when I said “[Chalmers] does not seem to believe in the nomological possibility of what we’ve called a biological zombie, and so Block is wrong to say that this sort of zombie is what Chalmers does in fact believe in” (although I was correct that Block accepts the nomological possibility of functional zombies). Here’s what Block said:
“The second sort of zombie is a creature that’s physically exactly like us. This is [David] Chalmers’s zombie, so when Chalmers says he believes in the conceivability and therefore the possibility of zombies, he’s talking about that kind of a zombie. My view is that no one who takes the biological basis of consciousness seriously should really believe in that kind of a zombie. I don’t believe in the possibility of that zombie; I believe that the physiology of the human brain determines our phenomenology and so there couldn’t be a creature like that, physically exactly like us, down to every molecule of the brain, just the same but nobody home, no phenomenology. That zombie I don’t believe in, but the functional zombie I do believe in.”
I took Block to be saying that he rejects the nomological (and logical?) possibility of biological zombies, and further that Block thinks that Chalmers accepts the nomological possibility of biological zombies (which he doesn’t). Block is definitely saying that Chalmers accepts a conception of zombies that Block thinks should properly be rejected, and at the very least that must mean the nomological possibility of a biological zombie, and it seems to be this he has in mind (“the physiology of the human brain determines our phenomenology and so there couldn’t be a creature like that, physically exactly like us, down to every molecule of the brain, just the same but nobody home, no phenomenology”). But because Chalmers rejects this the nomological possibility of a biological zombie, I suggested that Block was wrong to say that this is the sort of zombie Chalmers in fact believes in. So I’m still a little bit lost by this response (though perhaps this isn’t the best characterisation of his position – Block can also be read here as arguing against the logical, not just nomolgical, possibility of a biological zombie, in which case the mistake he thinks Chalmers makes is to suppose that this is conceivable - which Chalmers does claim).

From the feedback I’ve had, and re-looking at what the philosophers said, my tally up should have been the following. Chalmers believes in the logical possibility of both functional and biological zombies, but rejects the nomological possibility of both (Chalmers says “I think that even a computer [in this world] which has really complex intelligent behaviour and functioning would probably be conscious” – in other words, a functional zombie is not nomologically possible). Block, contra Chalmers, accepts the nomological (and also logical) possibility of functional zombies, but not biological zombies (not quite sure what he thinks about the logical possibility of biological zombies). Searle accepts the nomological possibility of functional zombies, and the logical possibility of biological zombies, but rejects the nomological possibility of biological zombies.

So that’s what I should’ve said.

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