Illusionism and a Posteriori Physicalism: No Fact of the Matter

Illusionists and a posteriori physicalists agree entirely on the metaphysical nature of reality — that all concrete entities are composed of fundamental physical entities. Despite this basic agreement on metaphysics, illusionists hold that phenomenal consciousness does not exist, whereas a posteriori physicalists hold that it does. One explanation for this disagreement would be that either the illusionists have too demanding a view about what consciousness requires, or the a posteriori physicalists have too tolerant a view. However, we will argue that this divergence of opinion is merely an upshot of the semantic indeterminacy of the term 'conscious' and its cognates. We shall back up this diagnosis by showing how semantic indeterminacy of the kind in question is a pervasive feature of language. By illustrating this pattern with a range of historical examples, we shall show how the dispute between the illusionists and a posteriori physicalists is one instance of a common kind of terminological imprecision. The disagreement between them is thus not substantial. In effect, the two sides differ only about how to make an indeterminate term precise. The moral is that they should stop looking for arguments designed to settle the dispute in their favour.