Lord, you add understanding to faith. Therefore, as far as it is profitable for me, let me understand that you exist, in the way I believe you exist; and that your nature is what I believe it to be. I believe you to be that above which nothing greater can be conceived. But something above which nothing greater can be conceived, cannot exist only in the mind. If it exists in the mind, it is possible for it to exist in reality; and if it exists in reality, it would be greater than merely existing in the mind.
St. Anselm of Canterbury: Proslogion 2