I have long been convinced that it is distressingly easy to misunderstand individual strands of Kant's moral thought apart from the context of his entire moral theory. There are some fine brief overviews of Kant's moral theory, such as H. B. Acton's Kant's Moral Philosophy, John Kemp's Philosophy of Kant, S. Körner's Kant, and Roger Scruton's Kant. But the very brevity of these studies prevents them from doing justice to the intricate complexity of Kant's theory. Many other books and articles concentrate on only one part of the Kantian corpus, but since no one of Kant's books contains his entire moral theory, those works also tend to be incomplete in important ways. My aim in writing this book is to set out a synoptic and detailed exposition of Kant's entire practical theory.

Others have also felt the need for such a work. John Rawls, for example, has noted that “unfortunately, there is no commentary on Kant's moral theory as a whole.” I am grateful that a philosopher of his stature has shared my belief in the need for such a study, but I am also glad I did not come upon his further comment (“perhaps it would prove impossible to write”) until I was already so far along in my work that I had decided I would not be deterred by the difficulties Rawls had anticipated and with which I had become familiar.