Daniel C. Dennett
Knock-down refutations are rare in philosophy, and unambiguous self-refutations are even rarer, for obvious reasons, but sometimes we get lucky. Sometimes philosophers clutch an insupportable hypothesis to their bosoms and run headlong over the cliff edge. Then, like cartoon characters, they hang there in mid-air, until they notice what they have done and gravity takes over. Just such a boon is the philosophers' concept of a zombie, a strangely attractive notion that sums up, in one leaden lump, almost everything that I think is wrong with current thinking about consciousness. Philosophers ought to have dropped the zombie like a hot potato, but since they persist in their embrace, this gives me a golden opportunity to focus attention on the most seductive error in current thinking.
Todd Moody's essay on zombies, and Owen Flanagan and Thomas Polger's commentary on it, vividly illustrate a point I have made before, but now want to drive home: when philosophers claim the zombies are conceivable, they invariably underestimate the task of conception (or imagination), and end up imagining something that violates their own definition. This conceals from them the fact that the philosophical concept of a zombie is sillier than they have noticed. Or to put the same point positively, the fact that they take zombies seriously can be used to show just how easy it is to underestimate the power of the "behaviorism" they oppose. Again and again in Moody's essay, he imagines scenarios to which he is not entitled. If, ex hypothesi, zombies are behaviorally indistinguishable from us normal folk, then they are really behaviorally indistinguishable! They say just what we say, they understand what they say (or, not to beg any questions, they understandz what they say), they believez what we believe, right down to having beliefsz that perfectly mirror all our beliefs about inverted spectra, "qualia," and every other possible topic of human reflection and conversation. Flanagan and Polger point out several of Moody's imaginative lapses on these matters in careful detail, so I needn't belabor them. In any case, they follow trivially from the philosophical concept of a zombie.
Flanagan and Polger also fall in the very same trap, however. For instance, they say it is "highly unlikely--implausible to the extreme--that mentalistic vocabulary would evolve among Moody's zombies. But is it metaphysically, logically, or nomically impossible? No." Here getting it half right is getting it all wrong. It is not at all unlikely or implausible that mentalistic vocabulary would evolve among zombies. That must be conceded as part of the concession that zombies are "behavioral" twins of conscious beings; if it is likely that we conscious folks would develop mentalistic vocabulary, then it must be exactly as likely that zombies do. It is just such lapses as this one by Flanagan and Polger that feed the persistent mis-imagination of zombies and make them appear less preposterous than they are.
(The whole paper is now available in Daniel Dennett, Brainchildren, Essays on Designing Minds, MIT Press and Penguin, 1998.)