Recent comments on a recent post by Peter were (inevitably) inappropriate, so I thought I'd better post something here, regarding the causal closure of the physical world. That closure seems to be widely presumed (e.g. by Searle, and Chalmers, and those I've read less recently), presumably because of (what is said to be) overwhelming evidence (although some physicists disagree), but I'm wondering why? I doubt that it is simply a matter of a lot of evidence: cf. how not so long ago there was apparently overwhelming evidence that space was Euclidean (e.g. the huge explanatory success of the extremely neat Newtonian physics of the day), so much so that Kant (and Poincare etc.) could reasonably say that it was a matter of logic, not empirical evidence (rather paradoxically); and of course, modern physics (and the associated philosophy) is hardly so tidy.
......What there was (we now know) was a lot of evidence that space was approximately Euclidean (as we already knew) and about where to look for the non-Euclidean stuff (for Einstein). Similarly a (substantial) dualist about mind and body (such as myself) might expect non-closure to show up only in the details of the mind-brain interaction (e.g. via an explanatory gap remaining even with a completely detailed theory of the brain, or via observations of exceptional neurones directly and therefore unlikely, or via theoretically related phenomena beyond the brain, and so forth). The "overwhelming evidence" cited in defence of closure seems to lie far from where that is likely to be.