I think the answer is yet to be determined. We are just begining to peer into the physical basis for thoughts and memories. Any opinion on the origin of agency in our conciousness must necessarily be mostly conjecture. That said, past experience has shown that the explanation for natural phenomena has had a concrete physical basis in all cases where science has come to understanding. Why should a person's will be any different and therefore only free in the sense that it will respond independently to outside stimulus. Even if the basis of thought is solely chemical in nature, then there must be some element of randomness in the system. (i.e. ? thought mutation). Now, my free will is telling me to stop thinking so hard and grab a beer.
I would define choice as the introduction of freedom into a causal system, meaning an acausal interruption into an otherwise causal sequence (or the opposite, a causal interruption into an acausal sequence). In order to consider humans any different from rocks, we would have to be capable of such a feat. Otherwise, we are just lifeless, drifting husks of matter, acting only as we must.
DesCartes tried to posit that the pineal gland was the locus of man's ability to affect reality - where thought became action, but his guess bore no fruit (actually there are some rather interresting studies on the possible production of DMT in the pineal gland which could, in a roundabout way, end up lending some validity to Rene's theory, but hallucinogen production in the brain would only explain the feeling of choosing, not an actual means by which one might affect choice. The feeling would be an illusion. Which brings to mind a study done recently in which stimulation of the post-parietal cortex created a desire to move while, alternately, stimulation of the motor cortex triggered movement without the desire, thereby explaining at least one instance in which both the desire to move and the act of moving were created thorugh chemical stimulation.
Another study I recall, had subjects choose between pushing one of two arbitrary buttons. EEGs showed that the subject's "choice" could be predicted several seconds ahead of their physical movement, even before they were aware they had made a choice. This suggest to me that the feeling of wanting to perform an action is symptomatic of the process which causes it, rather than the feeling being the cause itself.
Will I have Salad or pizza for lunch? I've been putting on weight, I should have salad... but the pizza smells great... but my girlfriend would be pissed if I had pizza as she is on a diet... and the pizza is more expensive... and the TV told me that'd I'd get Heart disease if I ate lots of junk food...
Determinism is complicated. The amount of factors that effect a decision are immense, but they are all from pre-programming, past experiences, genetics, anything that has led to the moment you are in right now. just because some of them are brought to consciousness they get labeled "free will" rather than instinct... you still arrive at a decision based on knowledge and environment.
All systems in the universe respond in predictable ways (if they didn't science wouldn't work AT ALL), some of them are very very complicated, like the brain, and seem random before further research, but if we are to believe that science can actually explain the whole universe then we should reject free will - as free will would be completely ruining the predictability of the universe in any location where self aware beings could come in and enact their free will.
Hah, I love that we keep coming back to this discussion. I'm gonna send you a request to join my new group, maybe you can help me decide on how things really work in probably the most important way - how we determine what is good/bad and right/wrong.
Anyway sadly no, I haven't read DDI by DD. What I've read of Dennett's I've loved, but I am too busy writing these days to actually do much reading. I've got a lot of catching up to do. But the points you bring up are spot on. Even viruses may have choice. Obviously we've got a lot more choice, but this is a matter of difference of degrees, not differences in kind. People who argue for free will must really misunderstand what determinists mean by our arguments. We are not saying that choice does not exist, but neither are we saying that it is "free" as in unconstrained by reality and natural causes. But you've got to admit, it is sort of weird to say that we have choice but that it is more of an illusion than anything else. As weird as it may be, however, and as weird as evolution is and even existence (which is really quite bizarre if you think about it), the notion of free will makes still less sense. Weirdness abounds!