That free will was demonstrated in the placing of temptation before man with the command not to eat of the fruit of the tree which would give him a knowledge of good and evil, with the disturbing moral conflict to which that awareness would give rise.
I don't remember deciding to become a writer. You decide to become a dentist or a postman. For me, writing is like being gay. You finally admit that this is who you are, you come out and hope that no one runs away.
The overwhelming majority of theories are rejected because they contain bad explanations, not because they fail experimental tests.