St thomas Aquinas’ Summa Theologiae is a masterpiece of systematisation, universally acknowledged as the finest example of what was a relatively new literary form that had emerged in the late twelfth century. Aquinas set himself to render Christian faith intelligible against the background of a scientific revolution that was taking place as a result of the rediscovery of Aristotle’s works of natural philosophy, which seemed to many to undermine Christianity. Aquinas took it for granted that sacra doctrina (what we now call theology), though rooted in revelation, is consistent with, even if it also exceeds, the deliverances of reason. In the Summa, he sought to demonstrate that theology’s intellectual credentials remained intact in this new situation, which some found exc