What must a person be like to possess a virtue in full measure? What sort of psychological constitution does one need to be an exemplar of compassion, say, or of courage? Focusing on these two examples, this book ingeniously argues that certain emotion traits play an indispensable role in virtue. With exemplars of compassion, for instance, this role is played by a modified sympathy trait, which is central to enabling these exemplars to be reliably correct judges of the compassionate thing to do in various practical situations. Indeed, according to the book, the virtue of compassion is, in a sense, a modified sympathy trait, just as courage is a modified fear trait. While the book upholds the traditional definition of virtue as a species of character trait, it discards other traditional precepts. For example, the book rejects the unity of the virtues and raises new questions about when virtue should be taught. Unlike orthodox virtue ethics, moreover, this account does not aspire to rival consequentialism and deontology. Instead the book repudiates the ambitions of virtue imperialism, and makes significant contributions to moral psychology and the theory of virtue alike.