This explains why Anselm upheld the Christian faith in his intellectual life and refused to accept any thought into his theories that did not hold up to the scriptures. .
For Anselm, faith must be the starting point in the search for the truth. In his quest, he decided that a human could not comprehend the mysteries of faith, otherwise they would not be mysteries, but he thought it possible to prove the necessity of the Trinity and the incarnation. Anselm stresses that he wants to find a proof of God, not because he does not believe, but because he does believe he wants proof of his belief. .
To prove the existence of God, Anselm proposed the now famous ontological argument. His philosophy explains God as "that than which nothing greater can be conceived." Simply stated, he argues that such a being must exist in reality as well as in thought, or it would be possible to conceive something greater. Given this vague statement, it is no surprise that some would say Anselm's argument is flawed. .
On the other hand, we have the views of Aquinas, which strongly disagree with Anselm and the ontological argument. Aquinas refuted that since we are in fact ignorant of the divine essence from which existence is presumed to begin we cannot hope to demonstrate the reality of a being whose true nature we cannot even conceive. Instead, Aquinas thought we must begin our insight with sensory experiences we do not understand and reason upward from them to their origin in something eternal. Aquinas" claim was that it was at least possible, and perhaps even desirable in some circumstances, to achieve genuine knowledge by means of human reason. Aquinas" philosophy resulted in five ways of proving God exists. .
The first of Aquinas" five arguments refers to the Platonian ideal that everything must be moved by something else. "Therefore it is necessary to arrive at a first mover, moved by no other; and this everyone understands to be God.