In
philosophy of mind, a zombie is a person with no
inner conscious experience. They may behave and act in a seemingly lucid manner, even providing the appropriate linguistic replies in conversation, but the behaviors are not accompanied by any
consciousness. As the popular phrase has it, "the lights are on, but nobody's home."
As discussed by such philosophers as Daniel Dennett and David Chalmers, the concept of zombies is useful for discussing the nature of intentionality. See also martians.