 The treatments in ST are deliberately brief. Aquinas writes in the preface that “our intent in this work is to develop those issues that concern the Christian religion in a way that suits the education of those who are just beginning.” Today, no one thinks of ST as a work for beginners, although its scope and concision make it a useful place to start. A serious engagement with Aquinas’s work, however, requires comparing ST with parallel treatments elsewhere, such as the earlier Summa contra gentiles (SCG) and the still earlier commentary on Lombard’s Sentences. Moreover, since all three of these long works are written as theological treatises, it is useful also to compare these discussions with his accounts in the more philosophically focused and often more detailed disputed questions. In general, given how much Aquinas wrote and how often he reconsidered the same issue from a slightly different perspective, a careful study of his work requires comparing multiple treatments of the same issue. And since he did not begin to circulate his work until he was 30, and lived for only two decades more, those various treatments tend to reinforce rather than conflict with each other. (Naturally, scholars have long debated whether his thought evolves on one topic or another, on which see Pini 2012.)