William of Ockham

William was born in the village of Ockham south-west of London, joined the Franciscans young and studied theology at Oxford, writing a Commentary on the Sentences and much logic, but never took his doctorate: in 1324 he was summoned to the papal court at Avignon to answer charges of heresy. The inquiry dragged on four years, during which he was drawn into the Franciscan dispute with Pope John XXII over apostolic poverty and concluded that the pope himself was a heretic.

In 1328 he fled Avignon with the head of his order to the court of the emperor Louis IV, then at war with the pope, and is said to have told him: defend me with your sword and I will defend you with my pen. Excommunicated, he spent the rest of his life in Munich writing political treatises against papal temporal power and arguing that imperial authority comes from the people, not the Church. He died in 1347, perhaps of the Black Death.

His philosophy is famous for economy: what can be explained with fewer assumptions should not be explained with more. Universals are not things but natural signs in the mind; only particulars are real. God is omnipotent and can produce any effect directly, so causation cannot be proved, only observed, and reason cannot demonstrate the soul's immortality or God's existence, which belong to faith alone. His logic was the most rigorous of the Middle Ages. The scholastic synthesis came apart in his hands, and Luther, Hobbes and Locke can all be traced back to him.