There's a school of thought that states that the brain operates at a quantum level, and there is a more classical view that it's all 'billiard balls', and some people are in between there somewhere and see the billiard balls setup as so complex that the knowledge about any initial configuration must always be incomplete.

Only in the classical 'billiard balls' universe would there not be free will, in every other situation there has to be some element that allows us to make choices for good or bad.

Interesting aside: if an omnipotent being would exist and we'd live in a classical billiard balls universe that being would be able to predict the outcome of its own creation which would obviate the need for creating stuff in the first place.

So 'free will' is a central tenet of almost every religion, and according to that we are given choices and how we make those choices determines whether we are 'worthy' or not.

Obviously it doesn't require religion to have free will but I find it interesting that religions have caught on to this so universally.

Good, if somewhat large book that touches on this subject: The emperors new mind, by Roger Penrose.