Now we believe that You are something that which nothing greater can be thought. Or can it be that nothing of such a nature does not exist, since the Fool has said in his heart, there is no God (II). *
Saint Anselms point in his argument for the existence of God is clear cut and simple to understand. He clearly sets forth the idea that if God is so great, than no greater being can be thought of or conceived. For one who already believes in God, this argument is meaningful and easy to accept, yet for the non-believer difficulties in acceptance can be overcome by St. Anselms philosophical statements set forth in the Proslogion.
Saint Anselm brings to light the belief that we are all created in Gods image, yet we are so marked by sin that even though we are his image, we can never be as great as him. In relation to this St. Anselm points out that he does not even attempt to attain the greatness of God, and that humans can attain fulfillment through believing and understanding Gods greatness. This leads to the ontological argument where St. Anselm professes what he believes and understands.
He proves this to the non-believer in his references to than-which-nothing-greater-can-be-thought statements and how even a fool can mentally conceive even though he does not understand; yet the impossibility of than-which-nothing-greater-cannot-be-thought is reason for Gods real existence. Additionally, St. Anselm provides if that-than-which-a-greater-cannot-be-thought can be thought not to exist, that-than-which-a-greater-cannot-be-thought is not the same as that-than-which-a-greater-cannot-be-thought, which is absurd (III).
Furthermore, St. Anselm returns to that-than-which-nothing-greater-can-be-thought in Chapter XV. Here St. Anselm reminds us that understanding this statement alone does not necessarily mean that we have total knowledge of God. Instead it means that God is greater than any idea we have about him; this does not mean that the argument is false, only that it is always possible to comprehend something greater than we already can comprehend.
Problems may arise with St. Anselms giving positive attributes of God: simply that whenever you have a concrete example of a positive attribute it is all the easier to come up with the negative attribute. Saint Anselm describes God as both merciful and impassible in Chapter VIII, but that sets the stage for critics to call God merciless, savage, and changing.
To me calling God savage would be a very difficult thing to do, yet for a non-believer this may be an easy thing to do and evidence. Another example can be found in Chapter XIII where God is referred to as limitless or eternal. This can lead to statements of God being limited or ephemeral. St. Anselm attempts to address this concern with references to things in one place and the inability of those things to be anywhere else at the same time the actuality of those things. How only the metaphysical God can exist everywhere without limits or boundaries.
Saint Anselms God is the greatest thing imaginable. The concept of understanding Gods greatness can only be pondered on because total understanding leaves nothing greater for our understanding. The reality remains that the greatest thing you can imagine or think of is God in all his glory and greatness.