While rights are indispensable to our moral and political thinking, they are also mysterious and controversial. What is it for someone to have a moral right to something? What kinds of creatures are capable of having rights? Which rights do they have? As long as these questions remainunanswered, rights will remain vulnerable to sceptical doubts. This book provides the moral foundation necessary to dispel these doubts. The author does this by constructing a coherent concept of a moral right and a workable substantive theory of rights. The former arises from his analysis of moral rights as morally justified conventional rights, while thenecessary justificatory framework is supplied by a consequentialist moral theory.