In this translation of Saint Thomas Aquinas’s The Treatise on Law, R. J. Henle, S.J., a well-known authority on philosophy and jurisprudence, fluently and accurately presents the Latin and English translation of this important work. Henle provides the necessary background for an informed reading of the Treatise, as well as the only in-depth commentary available in English on this text. The first section of the book contains an introduction to St. Thomas’s life, work, writings, and jurisprudence. Henle discusses the structure of St. Thomas’s magnum opus, Summa Theologiae, from which The Treatise on Law is excerpted. A brief section is included on Scholastic philosophy and also on St. Thomas’s approach to the study of law. Henle then examines Thomas’s definition of a law and the general doctrinal background for the Treatise. Finally Henle explores St. Thomas’s sources, including his use of auctoritates, or authoritative quotations drawn primarily from the Bible, Aristotle, St. Augustine, and St. Isidore of Seville. The second part of the book contains the Latin text of the Treatise presented unit by unit, each followed by the English translation and, when appropriate, by a comment. The Treatise on Law will be of interest to law students, lawyers, judges, and legal scholars. It will also appeal to those interested in St. Thomas’s legal philosophy, such as political scientists, theoretical sociologists, and cultural historians. For philosophers, especially beginners in medieval philosophy, it serves as a good introduction to the thought of St. Thomas.