Are Zombies Possible?
I'm not talking about the arm-ripping, brain-eating type of zombie, I'm talking about the philosophical zombie. In philosophy, a zombie is something that looks, acts, and talks in every way like a human, but there's no one home. These creepy entities have no thoughts, feelings, desires, or sense of self. If you think zombies could exist, then it's possible that everyone you know (including your spouse, parents, and children) is a zombie. As a physicist, I feel justified in ignoring these fantastical creatures: by assumption, there is no detectable difference between a zombie and a human. So what's the use in talking about them?
Would You Do It All Again?
One way of phrasing the free will issue is to ask, "If you were in the exact same situation, would you do the exact same thing, or could you have made a different choice?" This is often illustrated with Austin's Putt. Philosopher J. L. Austin wrote
Consider the case where I miss a very short putt and kick myself because I could have holed it. It is not that I should have holed it if I had tried: I did try, and missed. It is not that I should have holed it if conditions had been different: that might be so, but I am talking about conditions as they precisely were, and asserting that I could have holed it.
The problem with this sort of discussion is in the phrases "exactly the same" or "conditions as they precisely were." Presumably we are talking about conditions being microscopically the same: same position of the ball, of every blade of grass and every air molecule. Further, I must be in the exact same state myself: every atom and electron in my brain and my body must be in the exact same state.
If that is what is meant, then I think this is a profoundly uninteresting question.First of all, there is clearly no way to test this question on the macroscopic level. Even if we could get the ball in the right place and the external conditions precisely the same (which we can't, of course) my own internal state will be different on a second go-round, for I will have a memory of the first try. Secondly, we already know the answer: from a physical point of view, having the exact same (quantum) state of the system is no guarantee of the same outcome. Finally, it is not at all clear what this has to do with free will. Let's humor the questioner and suppose we were able to do the experiment: make ten absolutely identical copies of me and my environment, and observe what the ten copies do. Suppose we found that I did the exact same thing each time. What have we learned? Only that identical copies do identical things - not particularly surprising or interesting. Suppose, on the other hand, that the copies do different things. On the physical level, this is possible if some quantum randomness is getting amplified into behavioral differences, as already noted. This would indeed be an interesting result - but it's not clear whether we've learned anything about free will. We have merely slipped back to the question of whether the underlying physics is deterministic or indeterministic. And, as I argued in the previous post, (in)determinism isn't really a crucial issue for free will.
(As an aside, I note that our inability to perform the experiment is not just a matter of technological sophistication: it is actually impossible in principle to put someone or some thing into the exact same state if the world runs according to quantum mechanical principles. This is the famous no-cloning theorem, to which I will return in the next post.)
What About The Nefarious Neurosurgeon?
Dennett, paraphrasing Frankfurt, presents this scenario (Elbow Room, p. 132):
Jones hates Smith and decides, in full possession of his faculties, to murder him. Meanwhile Black, the nefarious neurosurgeion, who also wants Smith dead, has implanted something in Jones's brain so that just in case Jones changes his mind (and chickens out), Black, by pushing his special button, can put Jones back on his murderous track. In the event, Black doesn't have to intervene; Jones does the deed all on his own.
Is Jones responsible for the murder, Frankfurter asks, even though he could not have done otherwise?
My question: why would anyone waste time worrying about such ridiculous stuff?
Next time: All sphexish things considered.