Ben Blumson

Physicalism is incompatible with what is known as the possibility of zombies, that is, the possibility of a world physically like ours, but in which there are no conscious experiences. But it is compatible with what is known as the possibility of ghosts, that is, the possibility of a world which is physically like ours, but in which there are additional nonphysical entities. In this paper we argue that a revision to the traditional definition of physicalism designed to accommodate the possibility of ghosts inadvertently accommodates what is known as the possibility of inverted spectra, that is, the possibility of a world which is physically like ours, but in which colour experience is inverted. This consequence is unwelcome, because it is widely agreed that the possibility of inverted spectra is incompatible with physicalism. We argue for a revised definition of physicalism which resolves this problem. We then use our definition to argue that physicalism is not compatible with what is known as the possibility of blockers, that is, the possibility of a world which is physically like ours, but in which additional nonphysical entities have prevented the existence of conscious experience. This undermines Stephan Leuenberger's attempt to defend physicalism from arguments which purport to establish the possibility of zombies