- an a priori argument for the existence of God, asserting that as existence is a perfection, and as God is conceived of as the most perfect being, it follows that God must exist; originated by Anselm, later used by Duns Scotus, Descartes, and Leibniz.
- the traditional a priori argument for the existence of God on the grounds that the concept itself necessitates existence
- any analogous argument from the nature of some concept to the existence of whatever instantiates it
