I'm quite fond of the current theory that holds that there is no such thing as free will.
It has been proved that we react to situations
faster than the information needed to allow us to make that particular decision can physically reach our brains from the relevant stimulus. And these situations are
not those we normally associate with autonomic 'reflex' actions, such as (unconsciously) withdrawing one's hand from a flame, or breathing, or the beating of our hearts, but actions that we believe we are consciously thinking about and deciding to make.
That we appear to react automatically to such stimuli, but then our brain tricks us into believing that we actually performed the act because we thought about, and then decided to perform that act.
If this theory holds water, the ramifications are incredibly far reaching. Imagine a situation where you stand in the dock accused of a crime. The evidence against you may be water tight, but you could argue that science has proved beyond doubt that you cannot have
consciously decided to commit the crime.
I love the idea that we all think we're in complete control of our lives, but in fact we are being 'driven' by a series of automatic responses, and that conscious thought is merely an elaborate illusion.
On an evolutionary basis, it makes a lot of sense really. Our genes are far too clever to allow
genuine conscious thought to threaten their continued survival.