This book examines the idea of public justification, stressing its importance but also questioning the coherence of the concept itself. D'Agostino shows that the concept is composed of various values, interests, and notions of the good, and that no ranking of these is possible. The notion of public justification is thus shown to be itself contestable. In showing this to be so, D'Agostino undermines many current political theories that rely on the concept of public justification, including those by Rawls, Waldron, and Nagel.