In the course of making a somewhat different point, Tyler Cowen writes:
It’s funny how Bryan thinks he can cite my actions as evidence against the correct belief. That’s absurd; for instance I also don’t act as if determinism is true, but citing that doesn’t settle the matter.
That seemed reasonable at first pass, but then I did a bit of a double take: What would it mean, exactly, to “act as if determinism is true”? What are we imagining that people would do differently if they were convinced of determinism? I’m not even sure this is the sort of belief one could coherently import into practical reasoning with any effect: “My actions are predetermined; what should I do about it?” I may regard my next five decisions are preordained, but that doesn’t spare me the trouble of having to make them, which means treating them (counterfactually) as “open,” in some sense, during my deterministic process of deliberation—it means invoking an “if”. What would the alternative even look like?
Maybe we’re imagining that I shouldn’t blame people for their bad actions or credit them for their good ones, since they were fated to act that way? (But then can I be blamed for blaming or praising them inappropriately?) I’ve never seen why this is supposed to be a real worry: If the premise is that radically free will is necessary for the assignment of moral responsibility, and it turns out we don’t have radically free will, the obvious inference to make is… to reject the premise. More generally, I can’t think of any line of reasoning that moves from the truth of determinism to some important conclusion about how we ought to act differently without either collapsing into incoherence or relying on a premise far more controversial than the conclusion it’s meant to support.