Does it make sense to speak of creatures which behave exactly like conscious beings, but are not actually conscious? Such creatures are called Philosopher’s zombies, and they are very different from Hollywood zombies. Hollywood zombies are noticeably different from normal human beings, they drool, shuffle etc. However, when we use this definition of “Hollywood zombie” for philosophical purposes, we must remember that there are many Hollywood zombies who are not sufficiently behaviorally anomalous to land movie contracts. In this technical philosophical sense, if a zombie’s behavior deviates from the behavior of conscious beings in any way whatsoever, she (it?) is a Hollywood zombie.
I think that philosopher’s zombies could not possibly exist, because they are as self-contradictory as round squares. The following argument is one reason why. The logic of the argument is unassailable, so it will thus stand or fall depending on the truth of the three premises, which I will now defend in turn.
1) Zombies are possible if and only if subjective experiences are epiphenomenal.
Philosopher’s Zombies are possible only if there are mental states, often called qualia, which have no causal impact on the physical world whatsoever. If these qualia have any impact at all on the behavior of the creature that possesses them, then in principle another person could detect that impact, and consequently that creature would be a Hollywood zombie, not a philosopher’s zombie. There can never be such a thing as objective evidence for this kind of purely subjective consciousness, which means it would be epiphenomenal.
2) Subjective experiences are epiphenomenal if and only if we have a direct awareness of them.
Descartes claimed we have direct awareness of our mental states. It supposedly gives us absolute certainty, but granting this kind of certainty to our awareness of mental states gives second class status to our knowledge of everything else (including the mental states of other people). If we don’t have a direct awareness of our subjective states, how else could there be any reason for believing that they exist? We have already stipulated that there must be no evidence for their existence in the external world. Everyone agrees that there is no such thing as what Dan Dennett calls a zagnet i. e. an object which behaves like a magnet but lacks some kind of inner “magnetismo”. The only difference between a zagnet and a zombie is that we supposedly have a direct awareness of these epiphenomenal states which we possess and zombies lack.
3) There is no such thing as direct awareness.
See Sellars’ attack on the Myth of the Given and Quine’s on the second of the two dogmas of empiricism. These arguments are too complex to summarize briefly, but most people who have carefully studied them find them to be decisive. Check them out, if you can find the time. Also, anyone who has studied the physiology of perception knows that there is nothing direct about how we become aware of our sensations. There is lots of complicated processing going on; they don’t just jump into our awareness and say “hi , I’m the color red.”
Therefore, (by hypothetical syllogism and modus tollens) subjective experiences are not epiphenomenal, and zombies are not possible.
For my argument, I only need conditionals (if. . .then) not biconditionals (if and only if). However, I think the standard argument for zombies flips these conditionals around, (which is only possible with a biconditional), adds a modal operator, and creates an argument that looks like this.
A) If we have a direct awareness of our subjective experiences, then they could be epiphenomenal.
B) If our subjective experiences are epiphenomenal, then Zombies are possible.
C) We do have a direct awareness of our subjective experiences
Therefore, (by hypothetical syllogism and modus ponens), Zombies are possible.
The punchline of all this is that the best way to settle the zombie controversy is to refocus on the question of direct awareness. That is the only premise in this argument that both sides disagree on, and the two classic papers by Quine and Sellars, linked above, pretty much finished off the concept of direct awareness, as far as many of us are concerned. I hear it’s coming back, though, and I don’t think it’s a coincidence that many of its supporters also think that zombies are possible. Let’s redirect the zombie problem to the question of whether there is direct awareness. If direct awareness goes, zombies go with it.