Philoponus' treatise Against Aristotle on the Eternity of the World, an attack on Aristotle's astronomy and theology is concerned mainly with the eternity and divinity of the fifth element, or 'quintessence', of which Aristotle took the stars to be composed. Pagans and Christians were divided on whether the world had a beginning, and on whether a belief that the heavens were divine was a mark of religion. Philoponus claimed on behalf of Christianity that the universe was not eternal. His most spectacular arguments, where wrung paradox out of the pagan belief in an infinite past, have...