There are two kinds of knowledge law school teaches: legal rules on the one hand, and tools for thinking about legal problems on the other. Although the tools are far more interesting and useful than the rules, they tend to be neglected in favor of other aspects of the curriculum. In , Ward Farnsworth brings together in one place all of the most powerful of those tools for thinking about law. From classic ideas in game theory such as the “Prisoner’s Dilemma” and the “Stag Hunt” to psychological principles such as hindsight bias and framing effects, from ideas in jurisprudence such as the slippery slope to more than two dozen other such principles, Farnsworth’s guide leads readers through the fascinating world of legal thought. Each chapter introduces a single tool and shows how it can be used to solve different types of problems. The explanations are written in clear, lively language and illustrated with a wide range of examples. is an indispensable user’s manual for law students, experienced practitioners seeking a one-stop guide to legal principles, or anyone else with an interest in the law.