Anselm and Gaunilo on the Ontological Argument
A perfect island, and a fool who cannot believe
Venue: Anselm, *Proslogion* (1077–78); Gaunilo, *Liber pro Insipiente* (c. 1078); Anselm, *Responsio* (c. 1078).
The founding statement of the ontological argument and its first sustained refutation.
Anselm's *Proslogion* presented the first version of the ontological argument: God is "that than which no greater can be conceived"; such a being exists in the understanding (since even the fool understands the description); if it existed only in the understanding it would be less great than if it existed also in reality; therefore, on pain of contradiction, it exists in reality. Gaunilo of Marmoutiers, "on behalf of the fool" (Psalm 14), replied with a parody: take "that island than which no greater can be conceived"; the same reasoning would prove its existence, which is absurd. Anselm's *Responsio* distinguished: the argument works only for that-than-which-nothing-greater (uniquely necessary), not for any contingent maximally-perfect thing. The exchange is the founding document of ontological-argument literature, which continues — Descartes, Leibniz, Gödel, Plantinga — through to today.
Historical Context
Anselm wrote at the Abbey of Bec, then became Archbishop of Canterbury (1093). Gaunilo was a Benedictine monk at Marmoutiers; his reply was respectful and philosophically serious, not polemical.
Parties
The concept of "that than which no greater can be conceived" entails the existence of its referent; necessary existence is part of the perfection-set that defines God.
Key arguments
- Even the fool understands "that than which no greater can be conceived"; the concept is therefore in the understanding.
- A being existing only in the understanding is less great than one existing also in reality.
- If "that than which no greater can be conceived" exists only in the understanding, it is not that than which no greater can be conceived — contradiction.
- Hence such a being exists in reality. The argument relies on the unique maximality of God, distinguishing it from any contingent perfection.
Allied schools
The ontological argument's form, applied to other concepts (perfect island, perfect anything), produces absurdities; the move from conceptual perfection to existence is illicit.
Key arguments
- Parody: "an island than which no greater can be conceived" — the same reasoning would prove its existence, which is absurd.
- Conceiving a being's greatness does not entail its existence; otherwise we could conjure anything into reality by definition.
- The "fool" of Psalm 14 may well understand the words without granting their reality, just as one understands "phoenix" without believing in phoenixes.
- Distinguishing necessary from contingent maximality is itself the question at issue and cannot be assumed.
Allied schools
Dimensions Engaged
Observer
Observer · Metaphysical Agency: can the concept of a maximally perfect being entail the existence of its referent?
Matter
Matter · Ontological Status: is existence a perfection — a constituent of an entity's nature — or merely the positing of an entity that has its constituents?
Verdict in retrospect
Kant's critique (1781) — "existence is not a predicate" — became the standard modern objection, generalising Gaunilo's point. Modal versions of the argument (Hartshorne, Malcolm, Plantinga, Gödel) revive it with sophisticated formal apparatus; their soundness remains contested. The argument's structural appeal has outlasted every consensus that it had been refuted.
Related Debates
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Further reading
- Anselm, *Proslogion* and *Responsio* (in *Major Works*, ed. Davies & Evans, 1998)
- Plantinga (ed.), *The Ontological Argument* (1965)
- Oppy, *Ontological Arguments and Belief in God* (1995)