Interactionism and Physicality

Substance‐dualist interactionism faces two sorts of challenge. One is empirical, involving the alleged incompatibility between interactionism and the supposed closure of the physical world. Although widely considered successful, this challenge gives no reason for preferring materialism to dualism. The other sort of challenge holds that interactionism is conceptually impossible. The historically influential version of the conceptual challenge is now discredited, but recent discussions by Chomsky and by Crane and Mellor suggest a new version. In brief, the argument is that anything that interacts causally with physical things would have to be sanctioned by physics,and anything sanctioned by physics is ipso facto (as a matter of conceptual necessity) physical. I focus on the second premise. I show that plausible arguments for it are in fact fallacious and that counterexamples undermine it. Thus the argument fails: substance‐dualist interactionism cannot be ruled out on conceptual grounds alone.