Intended for advanced undergraduates, graduate students, and teachers, this new translation and exposition of the first two Questions of the Summa Theologiae explains the text in unprecedented detail. The famous "Five Ways" of Aquinas receive ample consideration. The arguments are placed in their larger context in Thomistic philosophy and traced back to first principles, which in turn are illustrated by examples and defended from common objections. All technical terms occurring in the text are defined or explained in both the commentary and the glossary. Throughout, attention is paid to the rationale behind the order in which Aquinas proceeds. 574 pages; includes three appendices, an index of primary sources useful to know in reading the first two Questions, and exhaustive glossary.