Philosophical Zombie

A philosophical zombie (or p-zombie) is a thought experiment in the philosophy of mind: a being physically and functionally identical to a conscious human being but with no subjective experience whatsoever. It processes information, produces behavior, and reports having experiences — but there is nothing it is like to be it. The concept, developed by David Chalmers, is designed to show that phenomenal consciousness is not logically entailed by any functional or physical description, and therefore that consciousness cannot be reduced to or explained by those descriptions. If a p-zombie is conceivable, the argument runs, then physical processes alone are not sufficient for experience.

Critics deny that p-zombies are genuinely conceivable — that the apparent conceivability is itself an illusion produced by failure to fully imagine what complete physical identity would require. The debate has not converged. What is certain is that the p-zombie argument is the sharpest tool for separating those who believe phenomenal properties are real and irreducible from those who believe they are functional or illusory. See also: Consciousness, The Explanatory Gap.