Christine M. Korsgaard presents an account of the foundation of practical reason and moral obligation. Moral philosophy aspires to understand the fact that human actions, unlike the actions of the other animals, can be morally good or bad, right or wrong. Few moral philosophers, however, have exploited the idea that actions might be morally good or bad in virtue of being good or bad of their kind - good or bad as actions. Just as we need to know that it is the function of the heart to pump blood to know that a good heart is one that pumps blood successfully, so we need to know what the...