Abstract: The concept of the rule of law is invoked for purposes that are both numerous and diverse, and that concept is often said to overlap with, or to require, an assortment of other practices and ideals, including democracy, free elections, free markets, property rights, and freedom of speech. It is best to understand the concept in a more specific way, with a commitment to seven principles: (1) clear, general, publicly accessible rules laid down in advance; (2) prospectivity rather than retroactivity; (3) conformity between law on the books and law in the world; (4) hearing rights; (5) some degree of separation between (a) law-making and law enforcement and (b) interpretation of law; (6) no unduly rapid changes in the law; and (7) no contradictions or palpable inconsistency in the law. This account of the rule of law conflicts with those offered by (among many others) Friedrich Hayek and Morton Horwitz, who conflate the idea with other, quite different ideas and practices. Of course it is true that the seven principles can be specified in different ways, broadly compatible with the goal of describing the rule of law as a distinct concept, and some of the seven principles might be understood to be more fundamental than others.