Consent works moral magic. Things that would otherwise be wrong to do to someone are, with that person's consent, made morally permissible. But what is consent, and how does it work? What can be taken for consent (perhaps wrongly) and with what consequences? How does consent come into being and pass out of it? How can consent be conferred, invoked and revoked? What is the role of social and legal norms in governing consent? How contextually sensitive should those norms be in applying to diverse settings, ranging from sexual encounters to prison hospitals to the poll booth? Those are the sorts of broad questions animating this book. It aspires to provide a comprehensive account of the social practice of consent, informed by deep reading in the history of ideas, philosophy, law, political science and sociology. thus serves, at one and the same time, as a guide for the perplexed social practitioner of consent and as a touchstone for philosophical attempts to theorize and to refine those existing practices.