According to Wikipedia.org, a philosophical zombie or p-zombie is a hypothetical being that is indistinguishable from a normal human being except that it lacks conscious experience, qualia, or sentience. When a zombie is poked with a sharp object, for example, it does not feel any pain. While it behaves exactly as if it does feel pain (it may say “ouch” and recoil from the stimulus, or tell us that it is in intense pain), it does not actually have the experience of pain as a putative “normal” person does.
The notion of a philosophical zombie is mainly a thought experiment used in arguments (often called zombie arguments) in the philosophy of mind, particularly arguments against forms of physicalism, such as materialism and behaviorism.
Philosophical zombies are widely used in thought experiments, though the detailed articulation of the concept is not always the same. There are, in effect, different types of p-zombies. What differs is how much exactly they have in common with normal human beings. P-zombies were introduced primarily to argue against specific types of physicalism, such as behaviorism. According to behaviorism, mental states exist solely in terms of behavior: belief, desire, thought, consciousness, and so on, are simply certain kinds of behavior or tendencies towards behaviors. One might invoke the notion of a p-zombie that is behaviorally indistinguishable from a normal human being, but that lacks conscious experiences. According to the behaviorist, such a being is not logically possible, since consciousness is defined in terms of behavior. So an appeal to the intuition that a p-zombie so described is possible furnishes an argument that behaviorism is false. Behaviorists tend to respond to this that a p-zombie is not possible and so the theory that one might exist is false.
One might distinguish between various types of zombies, as they are used in different thought experiments, as follows:
* A behavioral zombie is behaviorally indistinguishable from a human and yet has no conscious experience.
* A neurological zombie has a human brain and is otherwise physically indistinguishable from a human; nevertheless, it has no conscious experience.
* A soulless zombie lacks a soul but is otherwise indistinguishable from a human; this concept is used to inquire to what, if anything, the soul might amount.
However, philosophical zombies are primarily discussed in the context of arguments against physicalism (or functionalism) in general. Thus, a p-zombie is typically understood as a being that is physically indistinguishable from a normal human being but that lacks conscious experience.