Rules perform a moral function by restating moral principles in concrete terms, so as to reduce the uncertainty, error, and controversy that result when individuals follow their own unconstrained moral judgment. Although reason dictates that we must follow rules to avoid destructive error and controversy, rules—and hence laws—are imperfect, and reason also dictates that we ought not follow them when we believe they produce the wrong result in a particular case. In The Rule of Rules Larry Alexander and Emily Sherwin examine this dilemma. Once the importance of this moral and practical conflict is acknowledged, the authors argue, authoritative rules become the central problems of jurisprudence. The inevitable gap between rules and background morality cannot be bridged, they claim, although many contemporary jurisprudential schools of thought are misguided attempts to do so. Alexander and Sherwin work through this dilemma, which lies at the heart of such ongoing jurisprudential controversies as how judges should reason in deciding cases, what effect should be given to legal precedent, and what status, if any, should be accorded to “legal principles.” In the end, their rigorous discussion sheds light on such topics as the nature of interpretation, the ancient dispute among legal theorists over natural law versus positivism, the obligation to obey law, constitutionalism, and the relation between law and coercion. Those interested in jurisprudence, legal theory, and political philosophy will benefit from the edifying discussion in The Rule of Rules.