Liber pro insipiente

work by Gaunilo

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June 30, 2026

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Liber pro insipiente, or "In Defense of the Fool," is a work by Gaunilo, a 11th-century Benedictine monk. Gaunilo wrote this critique in response to St. Anselm of Canterbury's ontological argument for the existence of God. Anselm argued that the concept of a being greater than which nothing can be conceived inherently implies that being's existence. Gaunilo countered this by using an analogy: the idea of a "perfect island" does not guarantee the island's actual existence. His work challenged the logic of inferring reality solely from a concept.123

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Gaunilo
Gaunilo’s Liber pro insipiente (“In Defense of the Fool”) was a critique of the rationality of Anselm’s assertion that the concept of “that than which nothing greater can be thought” (i.e., God) implies God’s existence. Gaunilo argued by analogy, pointing out that one’s concept of a…
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Gaunilo’s Liber pro insipiente (“In Defense of the Fool”) was a critique of the rationality of Anselm’s assertion that the concept of “that than which nothing greater can be thought” (i.e., God) implies God’s existence. Gaunilo argued by analogy, pointing out that one’s concept of a…
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St. Anselm of Canterbury
Early life and career
…Gaunilo of Marmoutier, in the Liber pro insipiente, or “Book in Behalf of the Fool Who Says in His Heart There Is No God.” Gaunilo denied that an idea of a being includes existence in the objective order and that a direct intuition of God necessarily includes God’s existence. Anselm…
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…Gaunilo of Marmoutier, in the Liber pro insipiente, or “Book in Behalf of the Fool Who Says in His Heart There Is No God.” Gaunilo denied that an idea of a being includes existence in the objective order and that a direct intuition of God necessarily includes God’s existence. Anselm…
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