Abstract
The first question of Thomas Aquinas’s Summa Theologiae makes the argument that sacred doctrine is an Aristotelian science and, furthermore, the most certain of the sciences. According to Aristotle, this means that the first principles of sacred science must be certain. The normal modes of grasping the certainty of principles are either by demonstrating them by a higher science or by a direct grasp of them by the natural light of the agent intellect. Both of these avenues, however, are closed to sacred science. It would seem, then, that if sacred doctrine is a science, it can have no scientists in the wayfaring state. Aquinas unties this knot by proposing a third way of grasping the certainty of the first principles, namely, by faith. Only by the supernatural and graced assent of faith can the articles of faith be known as certain and allow sacred doctrine to fit into the mold of an Aristotelian science.