Restoring Guy, I wonder if you think probabilistic theories in physics could make any real trouble for the substantive claims of determinism?
Ellis, I'm not sure if those sorts of choices are actually "random," but if they are, and determinism is true, then it must be that such choices are possible in a deterministic world. Does the pattern make sense? I keep saying that I don't know how the universe or mind work, or if determinism is true, but if determinism is true, then it must be that none of the things we observe are actually incompatible with determinism.
Nexalacer, I never said that determinism has been proven or is the only scientific position. In fact, I specifically said in an earlier post that I didn't think it could be proven, and that there's nothing wrong with libertarian free will. I also said that Stefan holds the view that all matter in fact operates according to immutable physical laws, and that non-law-bound things do not exist (he advances this view in his UPB book). So if you're objecting to those claims by pointing to the difficulties involved in testing them, then I'll have to direct you to him. I don't personally hold either of those views for reasons very much like those which you alluded to.
You make a point I haven't heard anyone make before when you say "...possible choices made [by] humans are boundless, within the set of choices that do not violate the laws of physics, because the possible influences on the human mind are boundless." I'm really not sure why you think that this is relevant. Are you suggesting that minds are somehow able to freely select the things that will affect them, and therefore can guide their otherwise law-bound choices?
PCRS, it's clear that we experience what seems to be the ability to choose freely, and so no determinist could reasonably argue that we need to live as if our choices are predetermined. It's not possible to live as if our choices are predetermined; we have to make our choices! People who act differently as a result of accepting determinism are probably missing the point. If determinism is true, then it's true whether or not you believe it. If it's not meaningless to talk about responsibility, meaning, and choice, then if determinism is true, then determinism must not be incompatible with those things. And if determinism is incompatible with those things, and it's true, then not believing in it won't help.
As for how morality could play a role in a deterministic world, welcome to the battlefield. That question has been fought over for centuries, and I'm not touching it. Suffice it to say that "I believe that X has some property Y, but if I believed that determinism were true, then I would believe that X has the negation of property Y" has precisely no bearing on whether or not determinism is true, no matter how much it would suck to believe that X has the negation of property Y.