Modal Ontological Arguments

Inspired by the third chapter of Anselm's Proslogion, twentieth century philosophers including Charles Hartshorne and Alvin Plantinga developed “modal” ontological arguments for the existence of God. Such arguments use modal logic to infer God's existence from the premises that (i) God's existence is possible and (ii) if God exists, He exists necessarily. Like other ontological arguments, modal arguments have won few converts to theism; many commentators consider them question-begging or liable to parody. This article details how recent attempts to defend these arguments have tried to overcome these difficulties by drawing on modern accounts of the epistemology and metaphysics of modality.