The Proof of God

Scene: a monastery in 1077. "Candles flickered, monks dozed, and spiders crawled on walls streaked with rain and mildew [...] The drone of someone reciting the Psalms wafted in the damp air." And then Prior Anselm saw the light. Imagine, he said to himself, a being than which nothing greater can be conceived. If this being did not exist, then you could immediately conceive of one greater, which did. So the being must exist in fact, not just in your imagination. Therefore, God exists.

Convinced yet? Anselm's argument eventually became known as the "ontological proof" of God. Not everyone has been persuaded, but it has not ceased to nag at great thinkers. Even Bertrand Russell was surprised to find it so tricky to demonstrate the flaw. Witham's concise and elegant history of an argument concentrates mainly on Anselm and the subsequent engagements with him by Aquinas, Ockham and Descartes, while delighting in the intricacies of monastic and university politics, and dabbing in charming touches of colour. In particular, it demonstrates effectively that efforts over time to accommodate or rebut the ontological proof generated fruit in philosophy and science generally. "Proof", of course, can also mean test.