Lesson · 4 min Stretch
That Than Which Nothing Greater
In one line Anselm tried to prove God from an idea alone. Gaunilo’s island showed how to test such proofs.
Anselm, an Italian-born monk who became Archbishop of Canterbury, wrote the Proslogion around 1078. His motto was faith seeking understanding: he believed, and wanted to see by reason why what he believed was true.
He defined God as that than which nothing greater can be conceived. Even the fool who says there is no God understands the phrase, so the idea exists in his mind. But a being that existed in reality as well as in the mind would be greater. So if the greatest conceivable being existed only in the mind, a greater one could be conceived, which is a contradiction. Therefore it exists in reality.
A monk named Gaunilo replied with a perfect island: the same steps would prove it exists too. Kant later argued that existence is not a property that makes a thing greater.
Go deeper
Anselm answered Gaunilo that the argument works only for a being greater than which none can be conceived, not for the best island. Later defenders add that an island’s greatness has no upper limit. Descartes, Leibniz and, in the twentieth century, Alvin Plantinga offered new versions, some using the logic of necessity. Philosophers still disagree about where, if anywhere, the argument fails, which keeps it among the most discussed proofs ever written.
The perfect plan
A manager describes a project plan so good that it could not fail, then argues that since a plan that could fail would be worse, this one will succeed.
A colleague points out that the same reasoning would prove any described plan a success. Describing perfection in words does not deliver it. The real test is whether the plan works when it meets the world.
Try this today When an argument jumps from a definition to a fact about the world, ask what the definition alone can deliver.
Cite or share this lesson
A plain reference you can paste into notes or an essay:
Quest2Reason. “That Than Which Nothing Greater.” https://quest2reason.com/learn/lesson/that-than-which. Accessed 13 November 2026.
Sources
- Stanford Encyclopedia of Philosophy, “Saint Anselm” — Covers his life, his motto and the argument of the Proslogion.
- Stanford Encyclopedia of Philosophy, “Ontological Arguments” — Sets out Anselm’s argument, Gaunilo’s island, Kant’s objection and later versions.
- Anselm, Proslogion, chapters 2–4 (Deane translation) — The argument in Anselm’s own words.
- Gaunilo, In Behalf of the Fool, with Anselm’s reply (Deane translation) — The lost island, and Anselm’s answer that his reasoning fits one being alone.