Richard Marshall interviews Allen W Wood in 3:AM Magazine:
3:AM: Isn’t Kant’s view about freewill problematic – isn’t he saying we don’t have freewill but nevertheless we must assume we have? Is this part of his argument for saying that the highest good isn’t knowledge but faith?
AW: Kant is not saying — about freedom or any other subject — anything of the form: “Not-p but we must assume that p.” That’s close to self-contradictory, like Moore’s paradox: “p, but I don’t believe that p”.
What Kant thinks is this: We can’t coherently deny, or even decline to affirm, that we are free. Not only our moral life, but even our use of theoretical reason — on which we rely in rationally inquiring into nature — presupposes that we are free. Not only in order to act morally, but even to formulate theoretical questions, devise experiments, choose which ones to perform and what conclusions to draw from then — we must presuppose that we are free. That’s the sense in which it is true that for Kant “we must assume we are free.”
Kant thinks we can show that there is no contradiction in supposing we are free. We can also establish empirical criteria for free actions, and investigate human actions on the presupposition we are free. We can treat human responses to cognitions as involving law-like connections grounded on free choices which show themselves in our character. But we can never prove that we are free or integrate our freedom in any way into our objective conception of the causal order of nature. If the problem of free will is to see how freedom fits into the order of nature, then Kant’s basic view about the free will problem is that it is insoluble. He puts it bluntly: “Freedom can never be comprehended, nor even can insight into it be gained” (Groundwork 4:459).
Kant’s position is therefore indeed “problematic” in the sense that he thinks freedom is a permanent problem for us, both unavoidable and insoluble. As with many metaphysical and religious questions, Kant thinks they lie beyond our power to answer them. If you can’t stand the frustration involved in accepting this, and insist on finding some more stable position which affords you peace of mind and intellectual self-complacency, then you will find Kant’s position “problematic” in the sense that you can’t bring yourself to accept it. You may try to kid yourself into accepting either some naturalistic deflationary answer to the problem or some dishonest supernaturalist answer. It would be nice, wouldn’t it? if we could get comfortable about the problem of freedom. Kant thinks that we can’t.
More here.