St. Anselm
St. AnselmDefinition.com
God is able to exist just as a square circle exist (i.e. Mentally but incapable of being actualized without contradiction). By the same logic, God, or the greatest thing that one could imagine, if imagined, would be surpassed only by having that God exist in reality. Thus, by definition, it would be a contradiction in terms for the greatest thing existing to not be a real God.
