Ontological argument for the existence of God

An ontological argument sets out to prove the existence of a god from the nature of concepts alone. It is thus an a priori argument. The term "ontological argument" originates with Immanuel Kant (who rejected the argument form), though it can be traced, in various forms, back to the work of Aristotle.

The argument typically works via a reductio ad absurdum: it presents a certain concept (for example that of a maximally perfect being — a being that has every possible perfection), supposes that such a being does not exist, and then draws out a contradiction, thus proving that such a being exists. That being is then identified with god. In other words, the concept implies its own instantiation; if one grasps the concept of god, then one is committed to the existence of god. (A separate argument is needed to show that there can be only one instantiation of the concept — only one god.)

The best-known uses of the argument are to be found in the context of the Abrahamic religions, its earliest formulation being found in the Proslogion of the eleventh-century philosopher and theologian Anselm of Canterbury. It was rejected and argued against by the thirteenth-century philosopher and theologian Thomas Aquinas, and was for some time neglected, but the early modern period saw its revival. René Descartes presented what became probably the best-known form of the argument, but versions were devised by prominent philosophers such as Gottfried Leibniz and Baruch Spinoza. In the modern period, attempts have been made to devise up-dated versions of the argument, most notably by Norman Malcolm, Charles Hartshorne, and Alvin Plantinga.

Anselm's version was criticised by Aquinas and by Anselm's contemporary, Gaunilo. Descartes' version was criticised by many of his contemporaries, including Caterus and Pierre Gassendi, and later by such philosophers as as Kant, David Hume, and Gottlob Frege.

The differences between the different versions of the argument are generally a matter of the precise nature of the starting concept.

Bibliography

• Anselm of Canterbury (translated by Jonathan Barnes) Anselm's Proslogium or Discourse on the Existence of God. David Banach's Web site.
• Charles Hartshorne The Logic of Perfection. LaSalle, Illinois: Open Court, 1962.
• Norman Malcolm "Anselm's Ontological Arguments". Philosophical Review 69:1 (1960), pp 41–62. Reprinted in his Knowledge and Certainty: Essays and Lectures by Norman Malcolm. Ithaca, New York: Cornell University Press, 1975. ISBN 0801491541 (also in Plantinga [1965]).
• Alvin Plantinga The Ontological Argument from St Anselm to Contemporary Philosophers. Garden City, New York: Doubleday, 1965.
• Alvin Plantinga God, Freedom, and Evil. Grand Rapids, Michigan: Eerdmans, 1977.

External links

• Gaunilo: In Behalf of the Fool, and Anselm's Reply — the Mediæval Sourcebook
• Philosophers' Criticisms of Anselm's Ontological Argument for the Being of God — the Mediæval Sourcebook
• Gregory S. Neal "Anselm's Ontological Argument For the Existence of God", from Grace Incarnate (1990)