The most famous and influential of the medieval philosopher-theologians. Aquinas is noted for his synthesis of Christian theology with the philosophy of Aristotle. His general approach is summarized in the memorable dictum that “grace presupposes nature and nature perfects it.” He is most famous for the Five Ways, by which he demonstrated the existence of God as the First Cause of such things as motion and design and as the necessary being that is the cause of the contingent beings in the natural world.
Aquinas’s writings contain richly developed thinking on a comprehensive set of theological and philosophical topics, including ethics and political theory. Though Aquinas believed natural reason can prove that God exists, he did not think reason is competent to know God’s essence in this life, and he affirmed that many essential Christian beliefs must be accepted on faith because God has revealed them.1
1. C.Stephen Evans, Pocket Dictionary of Apologetics & Philosophy of Religion (Downers Grove, IL: InterVarsity Press, 2002), p. 12.