Book excerpt: While much has been written on both political obligation and the justification of punishment, there has been little sustained effort to link the two. In Playing Fair, Richard Dagger aims to fill this gap and provide a unified theory of political obligation and the justification of punishment that takes its bearings from the principle of fair play. To do this, he first establishes the principle of fair play-the idea that people in a cooperative venture have obligations to one another to shoulder a fair share of the burdens because they receive a fair share of the benefits of cooperation-as the basis of political obligation. Dagger then argues that the members of a reasonably just polity have an obligation to obey its laws because they have an obligation of reciprocity, or fair play, to one another. This theory of political obligation provides answers to fundamental and still debated questions about how to justify punishment, who has the right to carry it out, and how much to punish. Playing Fair brings two long-standing concerns of political and legal philosophy together to rebut those who deny the possibility of a general obligation to obey the law, to defend the link between political authority and obligation, and to establish the proper scope of criminal law.