In this new translation of Saint Thomas Aquinas's "Treatise on Law", R.J. Henle, an authority on philosophy and jurisprudence, provides the necessary background for an informed reading of the "Treatise" as well as an in-depth commentary on the text, in English. The first section of the book contains an introduction to St Thomas's life, work, writings and jurisprudence. Henle discusses the structure of 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" should be of interest to law students, lawyers, judges and legal scholars.It should 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 should serve as a good introduction to the thought of St Thomas.