Well, I had some notes for this post, but I seem to have temporarily misplaced them. Since I absolutely want to put something up on it, given how long it is since I have done so, here is something, dim shadow though it may be of my original intent.
Point #4: Choice is of means to non-singular ends.
We tend to treat the following (or some version of them) as true:
(1) We are capable of thinking of universals as such.
(2) We are capable of choosing to act in virtue of (at least some) such universals, taken as goals/ends/purposes.
If both of these are true, however, the libertarian has all that is needed for an account of free choice, since universals are not specified to the level of individuality. In other words, if we really are capable of choosing in virtue of universal ends (e.g., health, peace, good, justice, or anything similar), this suffices for a basic account of what free choice is. Under such a view, there is at least prima facie reason to think that we sometimes are not constrained to one alternative. The opposing view would be that, in fact, we don't really choose in virtue of universal ends, even part of the time; rather our choice is constrained with perfect precision to what actually ends up being chosen.
Of course, there is much more to be said, and if I had my notes I might say some of it; but as it is, my point here is basic: (1) and (2) make sense of free choice and, if true, give in themselves prima facie reason to think that at least some of our choices are not determined to one. Additional suppositions can be thrown up in order to circumvent this; but my point here is not to make an absolute argument, but to point out that such suppositions would, in fact, be needed by the determinist, if (1) and (2) are true; and each of these suppositions would have to be examined on its own. (What suppositions have been proposed have varied considerably from determinism to determinism.)
As I think I've previously noted in this series, there are actually two distinct issues that get conflated in most discussions of free will, so my next point, when I get around to it, will be to look at the other issue: free decision.