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William of Ockham
c. 1287–1347· Philosopher· Knowledge, logic & science
Well documentedSolid records, texts or physical evidence.
English Franciscan friar and logician who argued that only individual things exist and that general terms are merely names.
See it on the Philosophy map →The idea
The idea, called nominalism: there is no 'dogness' out in the world, only individual dogs; general words are signs in the mind. Ockham cut away many abstract entities that earlier thinkers had assumed. Summoned to the papal court at Avignon in 1324 on suspicion of heresy, he fled in 1328 to Emperor Louis IV after siding with Franciscans against Pope John XXII over Christ's poverty, and was excommunicated. The main objection: if no shared natures exist, why do individual dogs resemble each other so reliably?
Why it matters
His 'modern way' (via moderna) dominated late-medieval universities, loosened the bond between theology and philosophy, and his political writings argued for limits on papal power.
Legacy and sources
His logic textbook Summa Logicae, his commentary on Peter Lombard's Sentences and his political treatises survive; papal records document the Avignon inquiry and his excommunication.
Still debated
Whether he died of the Black Death in Munich around 1347 is uncertain, as is whether he reconciled with the Church before his death.
Inside this (1)
Connections (2)
▸William of Ockham challenged the realism of Thomas AquinasMostly agreed
The connection
Aquinas held a moderate realism: real shared natures exist in things, and the mind abstracts them. Ockham denied that any shared nature exists outside the mind; only individuals are real, and universals are just mental signs. He also doubted reason could prove much about God, separating theology from philosophy more sharply than Aquinas did.
When and how
Oxford and London, about 1317–1324, in Ockham's commentary on Peter Lombard's Sentences and in his Summa Logicae.
How sure are we?
Ockham's writings state and reject realist positions directly; historians trace the late-medieval split between the 'old way' of Aquinas and Scotus and Ockham's 'modern way'.
Debates and open questions
His main target on universals was often John Duns Scotus rather than Aquinas; how directly he engaged Aquinas himself is debated.
▸William of Ockham is credited with Ockham's razorDebated
The connection
Ockham used the principle of economy relentlessly, for example arguing that we need no separate entities for 'relations' or 'quantity' beyond individual things themselves. His frequent use made it his signature, so later writers attached his name to it, though he neither invented the idea nor wrote its famous wording.
When and how
Ockham's Oxford and London writings, about 1317–1324; the label 'Ockham's razor' appeared in the 1600s, and the familiar phrase came from John Punch in 1639.
How sure are we?
Phrasings such as 'plurality should never be posited without necessity' appear in his works; similar wording appears earlier in Aristotle, Grosseteste, Aquinas and Scotus.
Debates and open questions
Why his name stuck, rather than those of earlier or contemporary users like Durand of Saint-Pourçain, is unclear; some historians call it an accident of reputation.