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

It's often hypothesized that the structure of mental representation is map-like rather than language-like. The possibility arises as a counterexample to the argument from the best explanation of productivity and systematicity to the language of thought hypothesis—the hypothesis that mental structure is compositional and recursive. In this paper, I argue that the analogy with maps does not undermine the argument, because maps and language have the same kind of compositional and recursive structure.

Just as it’s possible to understand novel sentences without having heard them before, it’s possible to understand novel pictures without having seen them before. But these possibilities are often supposed to have totally different explanations: whereas the ability to understand novel sentences is supposed to be explained by tacit knowledge of a compositional theory of meaning for their language, the ability to understand novel pictures is supposed to be explained differently. In this paper I argue against this disanalogy: insofar as the ability to understand novel sentences is explained by tacit knowledge of a compositional theory, I argue, so is the ability to understand novel pictures.