I. Anselm of Canterbury (1033–1109)
A. Anselm adopted Augustine's motto of "I believe in order that I may understand."
B. He suggested that faith precedes reason in divine matters.
C. Anselm is famous for promoting the Ontological Argument for God's existence. In his work Proslogion, Anselm asserted that the idea of God is proof that God exists. As he stated, "We believe that you [God] are a being than which nothing greater can be conceived." He also said, "Hence there is no doubt that there exists a being than which nothing greater can be conceived, and it exists both in the understanding and in reality." Anselm's ontological argument is unique in that it is an a priori argument—an argument of the mind and not of experience.
D. Anselm is known for his arguments for the necessity of the Incarnation of Jesus Christ. In his Cur Deus Homo ("Why God Became Man"), he argued that Jesus' life and death were logical necessities. In doing so, he promoted what has become known as the "satisfaction theory" of the atonement.
According to Anselm, God is like a king whose honor has been offended. Since God's honor and justice have been trampled, there must be an appropriate satisfaction for these offenses. This "satisfaction," though, must be equal to the offenses. Since God is divine and humans are finite, there is no possible way that humans could pay the penalty needed to restore God's honor. Jesus being divine, though, was able to pay the satisfaction necessary. As both a representative of man and God, Jesus satisfied God's honor and made a right relationship with God possible.
II. Thomas Aquinas (1225–1274)
A. Aquinas was the most important theologian/philosopher of the Middle Ages. His ideas dominated Roman Catholic thinking until the Vatican II Council of the 1960s.
B. Aquinas merged Christian theology with the teachings of the ancient Greek philosopher, Aristotle. Although not the first person of his time to use Aristotle, Aquinas relied upon Aristotelian concepts when formulating his own views of philosophy and theology.
C. Aquinas offered five proofs for God's existence, which upon review can be distilled into two main arguments—the cosmological and teleological. The cosmological argument asserts that all existing and contingent things like the earth rely upon some uncaused being for their existence. For Aquinas, the earth came into existence by the Christian God, who himself does not have a cause. (Aquinas's cosmological argument parallels Aristotle's concept of the "Prime Mover" that started all things in motion.)
The teleological argument, which Aquinas also used, asserts that the incredible complexity in the universe points to an intelligent being that created it all. The universe, therefore, is not the result of blind chance.
D. Aquinas argued that there was a close connection between faith and reason. For most of its history, the church viewed faith as superior to reason and saw no need to justify the truths of Christianity by the use of human reason. Aquinas, though, viewed faith and reason as working closely together. In fact, he believed reason could be used to justify many elements of the Christian faith. Unlike some theologians before and after him, Aquinas felt that Christianity did not need to fear reason. When used correctly, it affirmed some of what God had revealed in the Bible.
E. Aquinas argued that nature reveals many truths about God. For example, studying nature could reveal to a person that God exists and that he is powerful. Thus, Aquinas believed we could learn about God by studying the world. Aquinas did not assert that everything we know about God comes from nature. There were some matters like the doctrine of the Trinity that could only be known through the Bible.