Ethical concepts are, or purport to be, normative. They make claims on us: they command, oblige, recommend, or guide. Or at least when we invoke them, we make claims on one another; but where does their authority over us - or ours over one another - come from? Christine Korsgaard identifies four accounts of the source of normativity that have been advocated by modern moral philosophers: voluntarism, realism, reflective endorsement, and the appeal to autonomy. She traces their history, showing how each developed in response to the prior one and comparing their early versions with those on the contemporary philosophical scene. Kant's theory that normativity springs from our own autonomy emerges as a synthesis of the other three, and Korsgaard concludes with her own version of the Kantian account. Her discussion is followed by commentary from G. A. Cohen, Raymond Geuss, Thomas Nagel, and Bernard Williams, and a reply by Korsgaard.

"The book is well worth reading..." International Studies in Philosophy

"This book is destined to replace Kant as the ultimate formulation of Kantian ethics. It should be required reading for any philosopher and should be in every library." W.F. Desmond, Choice

"This is a book anyone working in ethics should have on the desk. It is provocative and makes original and major contributions to a defense of a Kantian ethic. The historical developments of the various strands of thought are traced out in clear and helpful style. Korsgaard's writing is itself engaging and clear and her arguments forceful and for the most part compelling. This book constitutes a major advance in ethical theory." L. W. Colter, Review of Metaphysics