Vagueness leads to indeterminacies in the application of the law in many cases. This book responds to the challenges that those indeterminacies pose to a theory of law and adjudication. The book puts controversies in legal theory in a new light, using arguments in the philosophy of language to offer an explanation of the unclarities that arise in borderline cases for the application of vague expressions. But the author also argues that vagueness is a feature of law, and not merely of legal language: the linguistic and non-linguistic resources of the law are commonly vague. These claims have consequences that have seemed unacceptable to many legal theorists. Because law is vague, judges cannot always decide cases by giving effect to the legal rights and obligations of the parties. Judges cannot always treat like cases alike. The ideal of the rule of law seems to be unattainable. The book offers a new articulation of the content of that ideal. It argues that the pursuit of justice and the rule of law do not depend on the idea that the requirements of the law are determinate in all cases. The resolution of unresolved disputes is an important and independent duty of judges-a duty that is itself an essential component of the ideal of the rule of law.