Philosopher

William of Ockham

c. 1287 – 1347

Also known as Occam

Franciscan logician and nominalist, remembered for "Ockham's Razor", the principle that we should not assume more entities than we need.

Faint pen sketch of a hooded friar, labelled in Latin — Sketch labelled "frater Occham iste" in a 1341 manuscript of his Summa of Logic, drawn in his lifetime. Gonville and Caius College, Cambridge.Gonville and Caius College, Cambridge · Public domain · See the original

William of Ockham was an English Franciscan who studied and taught at Oxford. Summoned to the papal court at Avignon to answer charges about his teaching, he became caught up in a dispute with Pope John XXII over the poverty of Christ and the apostles, fled in 1328, and spent the rest of his life under the protection of the Emperor Louis IV, mostly in Munich.

He is the leading nominalist of the Middle Ages: he held that only individual things exist, and that universals such as “humanity” are names or concepts that apply to many individuals. The principle of economy that bears his name, not to multiply entities beyond necessity, sums up his approach, though he never used that exact phrase.

Key ideas

Ockham’s razor: We shouldn’t accept a claim that requires more kinds of thing to exist than a rival claim does, unless reason, experience or Scripture gives us grounds. The famous slogan “do not multiply entities beyond necessity” isn’t in his texts, but the sentiment is his.
No universal things: There is no universal “felinity”, only individual cats that resemble one another. The only universals are concepts and words, which are “universal” only because they apply to many things.
Only substances and qualities: Of Aristotle’s ten categories, Ockham thought only two name real kinds of being, substance and quality. The others are kinds of term, not kinds of thing.
Mental language: Ockham was the first to work out in detail the idea of a language of thought. Spoken words vary by convention (“dog”, “chien”), but the concepts they express signify things by nature and combine into mental sentences.
God’s commands: Ockham’s ethics includes a strong dose of divine command theory. Certain acts are required, allowed or prohibited for no other reason than that God commands it.

Tradition: Western
Region: England and Munich
Schools: Scholasticism
Period: Medieval

Influences

Influenced by

William of Ockhamc. 1287 – 1347

Influenced by

William of Ockhamc. 1287 – 1347

Where these links come from

William of Ockham drew on Aristotle. Source: Paul Vincent Spade, Claude Panaccio and Jenny Pelletier, William of Ockham, Stanford Encyclopedia of Philosophy
William of Ockham argued against John Duns Scotus. Source: Paul Vincent Spade, Claude Panaccio and Jenny Pelletier, William of Ockham, Stanford Encyclopedia of Philosophy

Key works

Summa of Logic (Summa Logicae), c. 1323

Often attributed, but not said

Entities must not be multiplied beyond necessity.
A later slogan for “Ockham’s Razor”: the principle is his, but this wording is nowhere to be found in his texts. Source: William of Ockham, Stanford Encyclopedia of Philosophy

Sources

Paul Vincent Spade, Claude Panaccio and Jenny Pelletier, William of Ockham, Stanford Encyclopedia of Philosophy