Summa Theologica

The Summa is organized around the exitus-reditus pattern: the procession of all things from God and their return to God as their final end. Part I treats God and creation (the exitus); Part II treats the return of rational creatures to God through virtue, law, and grace; Part III treats Christ and the sacraments as the means of that return. This framework rejects the view that theology is a disconnected collection of topics; it presents sacred doctrine as a unified science whose first principles are revealed by God . The Summa also rejects the view that philosophy and theology are in conflict: Aquinas argues that philosophical truths cannot contradict revealed truths, since both come from God, and that philosophy serves as the handmaid of theology.

Aquinas began the Summa around 1265 and worked on it until 1273, when he reportedly experienced a mystical vision and declared all his writings as straw by comparison, ceasing work on it. The Summa was left incomplete: it breaks off in the middle of Part III, and a supplement on penance and eschatology was added after his death based on his commentary on the Sentences. The work was first printed in 1485 by Peter Schöffer in Mainz, and the Leonine critical edition began in 1882 and is still in progress . The Summa survives in many manuscripts, and scholars have debated the relationship between the completed parts and the supplement, as well as the extent to which the text we have reflects Aquinas's final intentions.

Each article of the Summa follows a fixed structure: a series of objections, a sed contra citing an authority, a corpus articuli developing the master's position, and replies to each objection. The format is dialectical: the objections represent the strongest counterarguments, and the replies show why they fail. This structure was designed for the classroom, not for the library: the Summa was written for beginning students who needed a clear, orderly presentation of the whole of theology . The article format embodies a pedagogical method: it teaches students to see both sides of a question, to identify the strongest objections, and to reason toward a resolution. The Summa is thus not a collection of answers but an exercise in the practice of sacred doctrine.

The Summa was initially controversial: after Aquinas's death, it was attacked by some Franciscans, who disputed his positions on a range of issues. In 1277, some of his theses were condemned in Paris, and ecclesiastical authorities took a suspicious attitude toward his work . But the Dominican order defended him, and by the time of his canonization in 1323, he was regarded as a doctor of the church. The earliest criticisms concerned his use of Aristotle and his philosophical positions on the soul, knowledge, and the relation of faith and reason. Modern critics have raised different objections, including the adequacy of the article format for systematic theology and the question of whether the Summa's treatment of certain topics—such as punishment and sexuality—is defensible today.

The Summa is the mature successor to the Commentary on the Sentences. The Commentary was written in the 1250s, when Aquinas was a bachelor at Paris, and it follows the structure of Peter Lombard's textbook. The Summa, begun around 1265, is a more streamlined and pedagogical work, designed for beginners rather than advanced students. It treats the same topics but in a different order, with a more explicitly systematic framework (exitus-reditus) and a more concise article format . The Commentary remains valuable for tracing the development of Aquinas's thought, but the Summa is the work he intended as his definitive statement. Many of the positions developed in the Commentary are revised or refined in the Summa, and scholars often compare the two to track changes in his thinking.

The most common misunderstanding is that the Summa is a systematic textbook intended to present Aquinas's conclusions without ambiguity, a summa of answers. In fact, it is a pedagogical work designed for disputation: the article format preserves the objections, and the replies often qualify the conclusion rather than state it once and for all . A related misunderstanding is that the Summa is a work of philosophy rather than theology. Aquinas explicitly states that it is a work of sacred doctrine, whose first principles are revealed, and that philosophy serves as its instrument. Readers who approach it expecting a philosophical treatise will be surprised by its constant appeal to scripture and the Fathers. Readers who approach it expecting a closed system will find instead a living exercise in the practice of theology.