Arguments on God's Existence

Do you find Anselm's and Aquinas' arguments (proofs?) convincing? Why or why not?

I have read Anselm's argument many times over the years. It has always puzzled me. He argues, "And surely that than which is greater cannot be thought cannot exist in the mind only" (432). I understand that if it does not exist, than it cannot be the greatest thing that is thought. I do not understand how you can go from existing in the mind to existing in reality. Does it mean that if something exists in our mind must exist in reality. I assume the answer would be no for every thought, except the greatest thing that can be thought. So, I am not completely sure if I am convinced by Anselm's argument. I do think that it might convince me in another way. Why would the idea of God exist in our mind if He did not exist in reality? It seems having the concept of God leads to the conclusion that he exists. I guess a possible argument against this is the idea we can take things in our world and enlarge it to be some kind of god. I guess this is possible. It seems in the history of humans on earth that the vast majority of people believe in God. So, in some sense I believe having this thought makes one assume that God probably exists.

I think Aquinas's arguments are quite strong because he starts with effects in our world and shows how to explain these effects we must have a First cause. It is important to remember that Aquinas' Five Ways come after his opening questions about sacred doctrine. He asks first "whether besides philosophical sciences, any further doctrine is required." He answers in the affirmative. So he seems to be arguing that there are two ways to the knowledge of God: sacred doctrine and the philosophical doctrine. Second, the Summa was written for beginning theology students. Aquinas argues that the existence of God is not self-evident. He does not think Anselm's argument succeeds because we cannot know the essence of God or God who He is in Himself. He believes we need to know the essence of God for it to be self-evident to us. Aquinas argues that we know God exists because of the effects around us and the only valid explanation of the existence of these effects is that God exists. I find the Five Ways of Aquinas convincing. However, I wonder what we mean by proofs. Are proofs mean that we know God exists with certainly. It seems more like we can know God exists, but still have some doubts. The first way is from motion and change. To truly understand the Five Ways you probably need to understand Aquinas' metaphysics and the thought of Aristotle. Basically, in the first way for something to move or change, one has to be fully in act. There needs to be a first mover. The second way seems similar to the first way. He thinks if there is no ultimate cause, there cannot be efficient causes. Since no one can be the efficient cause of himself, there must be an ultimate cause that causes intermediate causes. It seems the third one is based on contingency and necessary beings. He argues that things go in and out of being. They are not permanent. If they can go out of being than there would be a time where nothing exists. Only a necessary being that is not dependent on other beings for his beings can cause beings to exist and sustain them in being. In other places Aquinas argues that there is a difference between essence and existence. God, however, is His own being. Aquinas' design argument seems to be strong. It does seem that non-intellectual things act for an end. It seems almost unbelievable for the preciseness of things for the world to exist. It seems hard to explain how this is true if God does not exist. I find the Five Ways quite convincing if one keep them in the context of Aquinas' complete writings.