Honestly, from a psychological standpoint, I think it's purposeless to consider that we might NOT have free will. It sure seems like we do, and to think that 'you' are not the cause of your behavior but rather the impersonal deterministic forces of the universe seems to open a lot of doors for scapegoating and devaluation of human experience. IMHO, it's difficult to see the value in the love my mother expresses for me if I consider the possibility that should couldn't have done otherwise. Then again, if the universe were deterministic, I suppose *I* couldn't help but see the value in her love-which-she-could-do-nothing-other-than-express.
I've been over the argument an hundred times, it seems. No, the universe doesn't appear to be deterministic because of quantum indeterminacy, but does that mean that my consciousness 'determines' the states of the particles that compose my brain and body? As far as quantum experimentation goes, there's no real support for that hypothesis, though I find it intuitively obvious that the spontanaeity of my behavior is not a strict consequence of only my environmental stimuli.
Then we consider possibilities like Many Worlds and Parallel Universes in which all probabilities actualize, and we wonder how we should regard this. If ALL real probabilities actualize,
then do we have determinism? It would seem so since all possible outcomes are necessary and unavoidable. But how do we account for the discrepency with macro-reality experience? Why don't we experience these alternative outcomes?
Too many questions, and not enough meaingful answers, IMHO.