Blogosophy

All You Zombies

A thorough article in the Stanford Encyclopedia of Philosophy explores Zombies of the philosophical variety (creatures behaviorally and possibly physically identical to you and me, but who lack any sort of consciousness). It's argued that if Zombies are even conceivable, some form of dualism must be true. Now, I find the idea of Zombies so absurd that I think almost any of the arguments advanced against it (as put forth in the above article) persuasive, which may be a problem since some of them may be contradictory, but without poking holes in the standard arguments against dualism (which as far as I can tell the Zombie-friendly don't do) it appears to me that the Zombie argument begins with a reductio. I.e. if the conclusion is dualism, there must be a mistake in one of your premises.

The argument for the possibility of Zombies goes:

1) Zombies are conceivable
2) What's conceivable is possible
3) Zombies are possible

From there it's reasoned that if Zombies are even possible, there must be something else going on that gives us conciousness and subjective sensations (qualia). I think if you buy that you ought to also buy the following:

1) It's conceivable that you are mistaken about having qualia
2) What's conceivable is possible
3) It's possible you are a Zombie

Hence the title of this post, taken from Heinlein's short story in which a man through time travel becomes his own origin and ends up saying "I know where I came from -- but where did all you zombies come from?"

As with the Zombie argument, you can argue against either 1 or 2, but the Zombie-friendly accept 2 so are left with arguing against 1. At first blush it might seem that 1 is eminently defeasible, since if Descartes's cogito ergo sum establishes anything it's that the subjective experience of qualia is self-validating. I don't think it's quite that simple, though, given how much more we now know about the brain and cognitive processing. We know for a fact that what might seem to introspection to be a single immediate sensation is actually a complex multi-stage process that takes place over time, involves various parts of the brain, involves subprocesses over which we have no conscious awareness, is sensitive to context and can be mistaken. For instance we know that we can easily mistake cold for hot, or see different shades of gray where there are none (c.f. the checkerboard illusion that was bouncing around the blogosphere recently); these might be taken as evidence that of course there are qualia--the mistaken impression is the qualia...but that has to be wrong: since Zombies are behaviorally identical, the Zombie would also report the mistaken impression. The mistake must occur at the physical level.

Consider this: when you introspect about qualia how do you know that's what you're doing? The you that is introspecting from moment to moment is a complex thing that's relying very heavily on memory (possibly among other things) for its sense of continuity, and we know how easily memory is mistaken. Isn't it conceivable that you are mistaken in thinking that you have qualia, when actually what you have is a mistaken memory of having had qualia. The memory of having had qualia is not necessarily evidence of qualia, any more than the Zombie's verbal report that it has qualia is necessarily evidence that it has them. If this seems farfetched, it's only because the act of introspection is not itself subject to introspection, even though it is known to be prone to error. That this is so is well documented empirically. For instance, take the case of the the patient described in Brain-Wise, by Patricia Smith Churchland with "anosognosia" (unawareness of illness):

Ramachandran studied one patient who, though very normal in other respects, believed that her motor functions were entirely normal, and specifically that she could move her paralyzed left arm and leg. She nonchalantly explained her presence in the hospital as owing to some minor problem. When asked to move her left hand, she would cheerfully agree to comply, and a moment later when queried about not complying, she would reply that indeed she just did move it. If asked to point at Ramachandran's nose, she would agree to do so, and later reply that yes, she could see her hand pointing directly at his nose.

Now, this is obviously some kind of introspection failure. One explanation of the failure is that the introspection worked, but there were hallucinatory qualia--but isn't it at least conceivable that there were no qualia at all, but the act of introspection itself failed and reported what the outcome would have been had there been sensory data and qualia? Remember that by the Zombie hypothesis everything about what actually happens in the perceptual system and reporting about it is completely explained at the physical level, so there cannot be a physical or perceptual difference between introspecting and actually having had qualia and introspecting and not having really had qualia (otherwise you could tell the difference between real people and Zombies by quizzing them on the act of introspection). If that still doesn't seem conceivable, consider some of the scenarios proposed by the Zombie-friendly in arguing for its conceivability where you slip in and out of the Zombified state (through plugging and unplugging your qualia): isn't it then conceivable that at any given moment you are Zombified, although your normal state is in force the moment before and the moment after, with the physical Zombie memories afterward indistinguishable from the ones that were "accidentally" accompanied by qualia? Isn't it conceivable you were a Zombie in the past, and will be in the future, even though you aren't right now? But if that's conceivable, isn't it conceivable that you are a Zombie even right now?

Do I believe this argument? No, I think it trades on the same laxity in what it means to be conceivable that the original Zombie argument does, although I think that the idea that we may sometimes misattribute qualia to ourselves may be in better empirical shape than the admittedly non-falsifiable Zombie hypothesis. There is necessarily something that it is like to be us--even though there may never have been a situation in which being us was exactly like what our memories prompt us to suppose it was. There is no possible universe where there are physically and behaviorally identical beings to ourselves who have nothing which it is like to be them, any more than (to use an example from Churchland) there is a universe which has physically and behaviorally identical beings that lack the property of being alive.