This is a very difficult question to answer. If all events, say at the atomic level, are caused by preceding events, then it seems to follow that all the atoms in the brain are simply moving in response to earlier atomic movements and are thus not in the control of the brain of which they form part. Laplace said that if atomic movements are all controlled by ealier movements, then if the position and other physical properties of all the atoms in the universe could be measured, then the future of the universe could be predicted; hence no free will.
However, Heisenberg's uncertainty principle says that the position and momentum of a particle cannot in principle be measured with precision, so Laplace's prediction could not be possible.
I imagine Theland would be interested in this stuff, as it could be said to fit in with his first cause belief. I don't think that first cause could be used to support free will, since after the first cause everything else could be a simple consequence of God's will and thus inevitable. There would need to be some 'mechanism' whereby non-physical 'mind-stuff' could exert an influence on physical things.