By the canon law of the Catholic Church, the Dominican Saint Thomas Aquinas (c.1225-1274), the Angelic Doctor, is to be embraced as a uniquely important teacher in the study of dogmatic theology. But it had not always been so. Aquinas’s defense of the rights of reason, philosophy, and nature within the realm of theology was controversial in the university and ecclesiastic world of the 13th century. The greatest of the high medieval scholastics, Aquinas and Bonaventure, were colleagues at the University of Paris, which grew out of the Notre-Dame cathedral school. Aquinas in particular had to thread a needle. On one side were Faculty of Arts masters which included radical Aristotelians (Averroists) tending in their rationalism to challenge the dominance of religion/theology over philosophy (more in the mold of Abelard). On the other side were theologians in the Augustinian tradition, who were suspicious of all Aristotelianism (a stance similar to that of al-Ghazali).

Aquinas composed his incomplete masterwork, the Summa theologiae, because he was concerned that moral theology and confessional practice were being taught to young Dominicans without sufficient systematic-theological context. The pattern defining most of the Summa is exitus-reditus [going-out-from-returning-to]: the proceeding of all things from God (creation) and their return to God in free moral action and ultimately through Christ. The following “questions,” an inherently dialectic genre, focus on the final end, or goal, of human life: happiness.