The papers collected in this volume examine moral enhancement: the idea that we should morally improve people through the manipulation of their biological constitution. Whether moral enhancement is possible or even desirable is highly controversial. Proponents argue that it is necessary if we are to address various social ills and avert catastrophic climate change. Detractors have raised a variety of concerns, some of a practical nature and others of principle. Perhaps most fundamentally, however, the proposal forces us to ask anew what being moral actually means, in order for the idea of moral enhancement to make sense at all. The present collection both addresses these issues and moves the debate beyond its current parameters, bringing together authors with a wide range of perspectives and areas of expertise. Chapters variously draw on experimental psychology, social philosophy, pragmatism, Kantian and Aristotelian moral philosophy, and the ethics of care, sex, and psychedelics.