Ontological argument

A family of philosophical arguments that infer God's existence from the concept or definition of God, rather than from empirical evidence.

Proslogion: An eleventh-century work by Anselm of Canterbury that presents his best-known ontological argument. Anselm’s argument appears in chapters 2 and 3 of this work.
Anselm of Canterbury: An eleventh-century theologian and philosopher who formulated the best-known early ontological argument. His definition of God supplies the starting point for the classic formulation.
A priori reasoning: Reasoning justified independently of particular sensory experience. The argument aims to establish existence through reasoning rather than observation.
Gaunilo's perfect island objection: A parody arguing that Anselm’s reasoning could seemingly prove the existence of a perfect island. It challenges whether the argument’s form can establish existence from a definition.
Greatest conceivable being: Anselm’s description of God as a being than which none greater can be conceived. The argument begins by analyzing what it means to conceive this being.
Gaunilo of Marmoutiers: An eleventh-century monk who criticized Anselm’s argument with a parody involving a perfect island. His reply tests whether Anselm’s reasoning could prove too much.
Essence: The properties that make a thing the kind of thing it is. Some versions claim necessary existence belongs to God’s essence.
Kant's objection to the ontological argument: Kant’s criticism that existence adds no real predicate to a thing’s concept. It denies the key move from possessing a concept to existing in reality.
Existence: The condition of being real rather than merely imagined or described. The argument’s disputed step treats existence as relevant to greatness or necessity.
René Descartes: A seventeenth-century philosopher who argued that existence belongs to the essence of a supremely perfect being. Descartes recast the argument through the relation between essence and existence.

Linked from 9 pages