I’m increasingly confused by what Goff’s argument is supposed to be. It seems like there are now three difficulties:

(a) How could there be a determinate answer about what function a physical system implements?

(b) How could a physical process account forthe addition function? (Goff gave something like this formulation in another comment)

(c) How could a physical process account for our knowledge of addition?

Supposedly, there is an argument against physicalism that follows from a puzzle for the view. Bracketing any evaluation of these puzzles, I’m just unsure which one is supposed to lead to the argument against physicalism.