Nominalism

The claim

Two white things have nothing literally in common. There is no whiteness in addition to the white things, and the resemblance we notice is not evidence of a shared constituent.

What it held

The problem was handed to the Middle Ages in a single paragraph. Porphyry, introducing Aristotle's Categories, asked whether genera and species exist in reality or only in the mind, and declined to answer. Boethius translated the question into Latin and the argument ran for five hundred years.

Roscelin gave the hard early answer — universals are mere puffs of air, flatus vocis — and was condemned for applying it to the Trinity, which shows how quickly the metaphysics became dangerous. Abelard produced the more defensible position: universals are words, but not arbitrary ones, since things genuinely resemble each other and words track that.

The stakes are not academic. If species are real, then human nature is something all people share and moral obligation has a foothold in the structure of the world. If they are only names, ethics and theology have to find another footing — and much of what happens after the fourteenth century is the search for one.

How it argued

Semantic analysis: showing that what looked like a metaphysical commitment is a feature of how words signify, and that no additional entity is required to explain it.

What it was arguing against

Realism about universals in every form — Platonic Forms, Aristotelian common natures, Scotus' formal distinction.

Where it disagreed with itself

Whether abandoning universals leaves resemblance unexplained, which is the standing objection and was never answered to the realists' satisfaction. Whether concepts in the mind are themselves a kind of universal, which would concede the point.

Common misconceptions

That nominalism is a medieval curiosity. It is one of the two live positions in contemporary metaphysics, defended by Quine and Goodman among others, and the argument has changed vocabulary rather than substance.

How it began

Roscelin's teaching in the eleventh century, sharpened by Abelard, and given its most rigorous form by Ockham two centuries later.

What became of it

Never resolved. The medieval phase closed with the via antiqua and via moderna as recognised alternatives, and universities taught both.

Lasting influence

Hobbes, Berkeley, Hume and Mill are all nominalists of some description. The twentieth-century versions — class nominalism, resemblance nominalism, trope theory — are refinements of positions first staked out here.

Why it still matters

Whether properties exist is a question every metaphysics course puts, and it is put in almost the terms Porphyry used.

Put another way

A pile of individually different stones, and a word for the pile that is not one of the stones.

Where to start

Porphyry's question first — it is three sentences — then Abelard's answer.

The surprising bit

Roscelin was condemned not for his metaphysics but for its consequence: if only individuals exist, the three persons of the Trinity look like three gods. Nobody could show he was wrong about that inference.

In their own words

Connections

Answers

Early Scholasticism

Opposed by

Old Academy, Thomism

Influenced

Ockhamism, British Empiricism

The verdict

A question asked in one paragraph in the third century and not settled in the eighteen since.

Sources

• Stanford Encyclopedia of Philosophy