Is unethical conduct necessarily irrational? Answering this question requires giving an account of practical reason, of practical good, and of the source or point of wrongdoing. By the time most contemporary philosophers have done the first two, they have lost sight of the third, chalking up bad action to rashness, weakness of will, or ignorance. In this book, Candace Vogler does all three, taking as her guides scholars who contemplated why some people perform evil deeds. In doing so, she sets out to at once engage and redirect contemporary debates about ethics, practical reason, and normativity. Staged as a limited defense of a standard view of practical reason (an ancestor of contemporary instrumentalist views), Vogler's essay develops Aquinas's remark about three ways an action might be desirable into an exhaustive system for categorizing reasons for acting. Drawing on Elizabeth Anscombe's pioneering work on intention, Vogler argues that one sort (means/end or calculative reasons for acting) sets the terms for all sound work on practical rationality. She takes up Aquinas's work on evil throughout, arguing that he provides us with a systematic theory of immorality that takes seriously the goods at issue in wrongdoing and the reasons for unethical conduct. Vogler argues that, shorn of its theological context, this theory leaves us with no systematic, uncontroversial way of arguing that wrongdoing is necessarily contrary to reason.