Substance

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Substance is the name philosophy gives to what underlies appearances — the reality that persists in a thing while its qualities come and go. A statue can be painted and repainted, chipped, moved, and remain the same statue; a person grows old, changes mind and mood, and stays one person. Substance is the answer to a stubborn question hiding under that observation: what is it that endures, and in what sense is it more truly the thing than any of its passing features?

The classical term is the Greek ousia, which Aristotle made the center of his account of being. For him the primary substances are individual things — this man, this horse — concrete particulars that exist in their own right rather than as features of something else. Everything else is said of them or exists in them: a color, a height, a relation, a place. These are the accidents, real but dependent, while the substance is what bears them and gives them somewhere to inhere. To ask what a thing fundamentally is, in this scheme, is to ask after its substance rather than its accidents. The word ousia derives from the verb “to be,” and the choice was deliberate: Aristotle held that of all the senses of “being,” substance is the one the others lean on.

Later thought pulled the term in several directions. Where Aristotle located substance in the individual, the Platonists located the truly real above the individual, in the Forms — so that for Plotinus the categories of being had to be rethought from the top down, the visible particular deriving its reality from a higher order rather than possessing it outright. The library holds his reworking of the Aristotelian categories in the sixth Ennead, and the problem of what genuinely is runs through Plato’s Sophist as well.

The most consequential migration was theological. When Greek-speaking Christians argued over the relation of the Son to the Father, ousia became the decisive word: the Council of Nicaea in 325 declared the Son homoousios, of one substance with the Father — a single Greek term on which the doctrine of the Trinity was made to turn, and over which the Church divided for a century. The Latin West rendered ousia as substantia, and from that root medieval theology built its account of how bread and wine could become the body and blood of Christ while every observable property stayed the same: the substance changed, the accidents did not. Whether such a notion is coherent has been disputed since, and the substance-accident framework that made it sayable was among the first casualties when early modern philosophy began to dismantle the Aristotelian inheritance.

What persists across these uses is the original intuition — that beneath the flux of what can be perceived, something holds steady and is more truly the thing. Much of metaphysics is the long argument over whether that something exists, and what it could be.

→ In the library: Plotinus — The Enneads (MacKenna, 1926): On the Kinds of Being · Plato — Sophist (Jowett, 1892)

→ Related: Nous · Logos · The One · Emanation · Neoplatonism