During the Medieval period, religion was advancing as well as the existence of God. Shortly after St. Augustine and his view on the “Problem of Evil” and his solution, which first introduced us to God and religion. Two other men came out with their reasons for the existence and essence in God and the world. These two men were Anselm and Thomas Aquinas. The focus of this paper will look at Anselm versus Aquinas proofs for God’s existence. I will mention here that Anselm believed in an ontological argument while Aquinas believed in a cosmological argument, these will be discussed more in depth in the next few paragraphs. First, I will introduce the two arguments made from Anselm and Aquinas. Next, I will explain how their approaches differ. Lastly, I will conclude on the success or not using their proofs. I will start off by introducing St. Anselm’s proofs for the existence of God. Anselm sets forth in his argument that not only does God exist, but that God also exists so truly that we can’t even comprehend that he doesn’t. This is called the ontological argument, which is a priori argument. Anselm starts his argument by giving us a definition for God, “that, than which no greater can be conceived” (pg. 260). Anselm’s argument moves from the essence of God to God’s existence, meaning that it moves from what God is to the fact that God is. His argument goes as follows, “God is that…show more content… His argument can be summarized down to this. We conceive God as a being that which no greater can be conceived. This being (God which no greater can be conceived either existing in the mind alone or both in the mind and in reality. His theory is prior to the independent of experience and true by the concept or definition for God alone. Whereas Thomas Aquinas is arguing a cosmological (posteriori) argument. He is arguing the effects (what is most known) to cause