This question is about the following famous argument (*) against free will:
If determinism is true, the will is not free.
If indeterminism is true, our will would just be a result of chance and we could not be responsible for it.
I'm mostly interested in logically convincing replies to the argument above, regardless how empirically or scientifically implausible they may seem.
If it appeals to something strange (for modern philosophers), like souls, special kinds of causation, ... all the better, because I believe that I may learn the most from it.
(*) One concrete example:
"The argument is exceedingly familiar, and runs as follows. Either determinism is true or it is not. If it is true, then all our chosen actions are uniquely necessitated by prior states of the world, just like every other event. But then it cannot be the case that we could have acted otherwise, since this would require a possibility determinism rules out. Once the initial conditions are set and the laws fixed, causality excludes genuine freedom.
On the other hand, if indeterminism is true, then, though things could have happened otherwise, it is not the case that we could have chosen otherwise, since a merely random event is no kind of free choice. That some events occur causelessly, or are not subject to law, or only to probabilistic law, is not sufficient for those events to be free choices.
Thus one horn of the dilemma represents choices as predetermined happenings in a predictable causal sequence, while the other construes them as inexplicable lurches to which the universe is randomly prone. Neither alternative supplies what the notion of free will requires, and no other alternative suggests itself. Therefore freedom is not possible in any kind of possible world. The concept contains the seeds of its own destruction."
(Colin McGinn: Problems in Philosophy: The Limits of Inquiry, 1993)