[Hererdebert]

based on these assumptions here is my reply:
1. We live in a closed physical universe.
2. That we have three areas to be considered as causal determinates: Physical, genetic and social.
3. that all of these elements are reducible to physical causality.
4. Free will is the idea that in a given situation, with the choice of a or b, a human is free to choose either without the influence of causal determinates.

Everything which I am, which makes me specifically me, is determined by my genetic make-up and the experiences which I have throughout my life. Both of these forms of causality are ultimately reducible to physical causality (although at a level of such complexity it doesn't bare thinking about). When I make a decision, I make it on the basis of my past experiences and my genetic predispositions. This is a deterministic view of human behaviour.
Looking at this view, it becomes clear that if you accept that the 'I' is a physically determined process (a story which we tell to ourselves and develops according to certain predefined and acquired constraints/predispositions). So every choice which 'I' make is caused by these different determined factors.
Looking at free will then: As defined in my 4th assumption free will can be characterised by the idea that if I went back in time to exactly the same point, with exactly the same conditions determining the situation, I could make a different decision each time. I.E., If I chose A the first time and then went back to that exact point, and all the determining factors (internal and external) were the same then I could still choose B.
Comparing the two, in the first we say that everything which makes 'I' 'I' determines the decisions which I make. In the later we see a situation in which 'I' (ie, our history, genetic make up and predispositions) has no determining role in our decisions.
In short, this notion of free will is a coin toss at the centre of human functioning. I personally find this to be a horrifying idea. I have no interest in believing that my acts are essentially random and uncaused.