Commentary on the Sentences Book I, Distinctions 21-48

The Sentences of Peter Lombard was the standard theological text from the twelfth through the fifteenth century. Thomas Aquinas's Commentary on the Sentences (ca. 1252–1256) was written by a young Aquinas in fulfilling the qualifications for becoming a teaching master at the University of Paris; it is perhaps the most comprehensive and detailed of all his works. The Commentary on the Sentences is not a commentary in the sense of a line-by-line analysis of the Lombard's text, but instead, it is the product of lively classroom discussion, in which Aquinas enjoys the liberty to take up any inquiry inspired by the text, treating topics not found anywhere else in his opus. The first book of the Sentences is concerned with questions revolving around the mystery of the Most Holy Trinity.