In section 40 of A Theory of Justice, John Rawls wisely notes that it is a mistake to view Kant's ethics with undue emphasis on the problems of the generality and universality of the moral law, that Kant's moral theory “as a whole” must always be kept in mind, and that this latter goal requires attention to the later writings on politics, religion, and teleology. It is certainly true that any fair inspection of the texts considered by Kant to be parts of his practical philosophy does reveal that he by no means regarded that philosophy as exhausted by the problem of the single, pure criterion by which the permissibility of individual actions could be judged. He obviously believed that he could produce a rich, rationally defensible theory of morals (Sitten) as well as a theory of morality, and Rawls is certainly right to suggest that we distort and cannot properly assess Kant's view of the foundations of this whole if we neglect to look to the “building” that these foundations were to support.

However, it is also fair to note that the chief reason commentators have concentrated so heavily on the logical problems of universalizability and moral judgment has not been willful neglect of the rest of Kant's moral theory, but the fact that it has never been clear how to put all the parts together.