What is a philosophical zombie?

A philosophical zombie, often called a p-zombie, is a being in a thought experiment that is physically identical to a normal human being but has no phenomenal experience. By definition there is nothing it is like to be one. It is unlike the undead creatures of film: it looks and acts like any other person. [1] [2] [3]

The Philosophy Now article describes a zombie version of you that would walk, talk and act as you do. If stabbed, it would scream and try to get away, but the screaming would not be accompanied by any feeling of pain. If a brain scientist examined you and your zombie twin, she could not tell the two apart. The Stanford Encyclopedia entry on qualia puts it as a molecule-by-molecule duplicate that processes stimuli the same way and produces the same behavior, yet experiences nothing at all. [4] [5]

The physical identity matters. The Stanford Encyclopedia entry on zombies notes that many physicalists already accept that a creature matching us only in behavior or function might lack qualia, the properties by which experiences are classed by what they are like. To challenge physicalism, a zombie must match us in all physical respects and be subject to the causal closure of the physical. [2]

Zombie arguments are used against forms of physicalism and in defense of the hard problem of consciousness, the problem of accounting in physical terms for subjective, first-person experience. David Chalmers, who makes the most systematic use of the idea against physicalism in his 1996 book, argues that the hard problem can be put as the question of why we are not zombies. In his view, everything in physics and neuroscience seems compatible with our being zombies, so no purely physical explanation can explain why we are not. [1] [2] [6]

Nobody believes philosophical zombies really exist, and the usual assumption is that none of us is a zombie. Chalmers says most people doubt they could exist in the actual world, meaning they are naturally impossible. The central question is whether they, or a whole zombie world, are possible in some broader sense. [4] [2] [3]

Many people hold that zombies are at least logically possible, meaning the idea is internally consistent, unlike a round square. Chalmers draws strong conclusions from this. The Stanford Encyclopedia says that if zombies really are possible, then physicalism is false and some kind of dualism is true, though it frames this as a conditional and says many hold only that zombies are conceivable. The search results here do not set out the main objections to the argument in detail. [3] [6] [2]