Abstract: This chapter begins with a sharp distinction between two kinds of judicial authority—the authority to apply law and to do equity. Plaintiffs who file suit on a claim of legal right assert an entitlement to recourse from the defendant, and to judicial assistance in obtaining it. By contrast, equitable claims request a court to exercise its discretion to block or modify the ordinary operation of the law, or to provide relief to which there is no legal entitlement. This distinction, we argue, sheds light on some of American law’s most famous and controversial decisions, including Riggs v. Palmer, Moore v. Regents, and Shelley v. Kraemer. Indeed, insofar as each reaches a defensible result, it is because it is an instance of a court doing equity rather than applying law. As our analysis of these and other decisions demonstrates, an appreciation of the law-equity distinction remains necessary for an adequate understanding of Anglo-American legal systems.