Constitution and the Explanatory Gap

Proponents of the explanatory gap claim that consciousness is a mystery. No one has ever given an account of how a physical thing could be identical to a phenomenal one. We fully understand the identity between water and H ₂O but the identity between pain and the firing of C-fibers is inconceivable. Mark Johnston [Journal of philosophy (1997), 564-583] suggests that if water is constituted by H₂O, not identical to it, then the explanatory gap becomes a pseudo-problem. This is because all "manifest kinds"-those identified in experience-are on a par in not being identical to their physical bases, so that the special problem of the inconceivability of 'pain = the firing of C-fibers' vanishes. Moreover, the substitute relation, constitution, raises no explanatory difficulties: pain can be constituted by its physical base, as can water. The thesis of this paper is that the EG does not disappear when we substitute constitution for identity. I examine four arguments for the EG, and show that none of them is undermined by the move from constitution to identity.