I disagree about whether it is an empirical question.
Reality has a set of behaviors and qualities that, by any other name, would still be as they are, and there are relationships which, regardless of how they are described, interact in fixed ways.
Algorithms, contingent mechanisms, freedoms of a system towards some outcome are empirically observable qualities of systems, regardless of whether we name or capture that in any other language than that of "that which exists as it is".
Metaphysics is the task of discovering the ways language must go together to remain coherent and descriptive of the underlying reality, and of "physical systems" in general.
That cannot be done unless the language used is based on empirical observation.
I would pose that intuition will get us close, but it will tend towards certain parts being almost comically wrong, too. When it comes time to start naming things formally, we should do our damnedest to see if there is something from the empirical side that seems to be fairly close to the idea suggested by intuition, and see if the "intuitive" side doesn't make more sense when through enforcement of the empirically derived language.
That is the process I used to describe free will using the language of algorithms, contingent mechanisms, and precursor conditions, no more and no less.
You’re right, it’s not entirely unempirical, but my point is that a key test for DBT’s claims — that we cannot do, other than what we do — can never be tested. That’s the crux of it.
Hard determinism itself is unscientific, because it does not seem subject to being tested by any of the tools in the suite of scientific methodologies. For example, falsification. Falsification isn’t a be-all and end-all for science, but it does have a place. Try to imagine a test to falsify hard determinism.
I can say, confronted with a choice between Pepsi and Coke, that I prefer Pepsi. But just to confute hard determinism, I choose Coke instead. And the hard determinist simply responds, “You were hard determined to try to refute hard determinism and that is why you picked Coke.“
It’s very like the religious belief that some hold, that God willed you to do what you did, and therefore whatever you did was God’s will.
As I have stated before, a simple demonstration of hard determinism would be if I attempted to drink Pepsi and some force, like an invisible hand, stayed my motion and forced me to grasp Coke instead. Needless to say, this has never happened to anyone — or if it has, to my knowledge no one has reported it.