Ghosts and sparse properties: why physicalists have more to fear from ghosts than zombies

Zombies are bodies without minds: creatures that are physically identical to actual human beings, but which have no conscious experience. Much of the consciousness literature concerns how threatening philosophical reflection on such creatures is to physicalism. There is not much attention given to the converse possibility, the possibility of minds without bodies, that is, creatures who are conscious but whose nature is exhausted by their being conscious. We can call such a 'purely conscious' creature a ghost. [opening paragraph]