A Deepness of Thought
It is impossible to do science without presupposing free will. Someone has to create the experiment and observe the results. This is a paradox. Science assumes the world is deterministic yet the observer cannot be.
We all behave as if we have free will. Some may believe that it is an illusion and if we only knew enough about the brain we could determine someone's thoughts and actions. But I do not think so. Studying the brain will only tell us what free will is not. It will tell us about the tools we have to observe and interact with the world. It cannot tell us what free will is in a deterministic way because science requires free will to exist in a non-deterministic way.
Historically, both determinism and non-determinism have been part of human thought since the beginning. But, historically, determinism has not held the dominant position in thought that it does today. Today, people get so amazed by the wonders of technology that they forget this fundamental paradox.
For me this paradox is a window to spirituality. I was raised Catholic, going to parochial schools and mass on Sundays. I struggled with religion in college and eventually gave it up. I agree with my educated friends that organized religion has a lot of superstition but I do not dismiss it as only being that.
Prior to free will and determinism, there is self awareness. To exercise free will you must be aware of "you". And, by extension, aware of others. A psychopath may have a brain defect that prevents this self awareness but that does not mean this awareness is a deterministic function of the brain. In means the brain is necessary for self awareness but not necessarily sufficient.
Dolphins are self aware in many respects, probably more self aware that any other species besides human. This would appear to be a case of convergent evolution. But convergent evolution occurs in similar environments and humans and dolphins have completely different environments. Science may one day resolve this but for now it would appear to be a fantastic coincidence. There is another possibility. Perhaps the evolution of self awareness is not completely deterministic.