Although Kant never developed what one might call a theory of the self, his virtual identification of selfhood with freedom provided much of the material used by his idealistic successors to develop their own theories. At the same time, however, Kant's actual account of freedom remains among the most perplexing features of his philosophy. One of the major problems is the bewildering variety of ways in which freedom is characterized in different Kantian texts. Thus, Lewis White Beck has distinguished between five different conceptions of freedom in Kant: empirical freedom, moral freedom or autonomy, spontaneity, transcendental freedom and postulated freedom. Since empirical freedom is non-problematic, while postulated freedom turns out to characterize the status of the non-empirical freedom that we supposedly possess rather than a distinct kind of freedom, and finally, since transcendental freedom (as applied to humans) is identified with the absolute spontaneity of the will, this list can be shortened somewhat. Nevertheless, this still leaves us with spontaneity and autonomy as distinct species of freedom: the former concerns rational agency in general, that is, the capacity to determine oneself to act on the basis of general principles (whether moral or prudential); the latter concerns moral agency in particular, that is, the capacity of pure reason to be practical (to determine the will independently of inclination or desire.)

It is sometimes claimed that the Wille–Willkür distinction, drawn in the Introduction to the Metaphysic of Morals, constitutes Kant's attempt to explain the connection between these two conceptions of freedom.