Kant claims in the Groundwork (G 4:448) that a rational will cannot act except under the Idea of its own freedom

A crucial move in Kant’s argument is his claim that a rational will cannot act except “under the Idea” of its own freedom (G 4:448). The expression “acting under the Idea of freedom” is easy to misunderstand. It does not mean that a rational will must believe it is free, since determinists are as free as libertarians in Kant’s view. Indeed, Kant goes out of his way in his most famous work, the Critique of Pure Reason, to argue that we have no rational basis for believing our wills to be free. Th