Ontological argument (Wikipedia)
An ontological argument is a philosophical argument, made from an ontological basis, that is advanced in support of the existence of God. Such arguments tend to refer to the state of being or existing. More specifically, ontological arguments are commonly conceived a priori in regard to the organization of the universe, whereby, if such organizational structure is true, God must exist.- Proslogion (Wikipedia)
The Proslogion (Latin: Proslogium, lit. ‘Discourse’) is a prayer (or meditation), written by the medieval cleric Saint Anselm of Canterbury in 1077–1078, serving to reflect on the attributes of God in order to explain how God can possess seemingly contradictory qualities. This meditation is considered to be the first-known philosophical formulation that sets out the ontological argument for the existence of God.