Matter

What a thing is made of, considered apart from what it has been made into.

Theme: Being and reality
Tradition: Greek
Term: ὕλη · hylē
Term fixed: c. 330 BC

In plain terms

Take a bronze statue and ask what it is. One true answer is: a figure of a man. Another true answer is: eighty kilograms of bronze. Matter is the second kind of answer.

It looks like the simpler of the two and it is not. The moment you try to say what matter is on its own, you find you can only describe it by what it has become. Bronze is copper and tin arranged a particular way; copper is atoms arranged a particular way; and at every level the description that identifies the stuff is a description of a structure.

So matter keeps receding. Whatever you point at as the material turns out to be something already formed, and the pure stuff underneath - if there is any - is by definition featureless and therefore impossible to describe.

As a philosopher would put it

For Aristotle matter is potentiality: what a thing is made from and what it could still be made into. It is always relative - bricks are the matter of a wall and are themselves formed clay - and pushing the regress downward gives prime matter, pure potentiality with no actuality of its own, which is either the necessary end of the analysis or a sign that the analysis has gone wrong.

Atomism is the rival account and older than Aristotle's: Leucippus and Democritus take matter to be indivisible particles moving in void, so that all apparent qualities reduce to arrangement. Lucretius transmits it, and the seventeenth century revives it.

Descartes redefines matter as extension, which makes it fully mathematisable and empties it of everything else, at the cost of making a vacuum impossible. The Sāṃkhya tradition takes a different route entirely, with prakṛti as an active principle carrying three qualities, not the inert stuff of the European account.

Where you meet it

An aluminium drink can put into recycling is shredded, stripped of its lacquer, and melted at about 660 degrees. It comes out as ingot, and about six weeks later it may be a window frame, a bicycle part or another can.

Nothing survives the process except the aluminium. Not the shape, not the printing, not the seams, not the function, not whatever it was that made it a can rather than anything else. What survives is precisely what the industry measures: mass and purity.

And the industry cares about purity because the metal is not simple either. Aluminium alloyed for a can body differs from aluminium alloyed for a lid, and mixing them degrades the result - which is Aristotle's regress running in a smelter. What looked like the plain stuff underneath turns out to be another arrangement, with a specification of its own.

What is actually disputed

Whether there is any matter as such.

Aristotle's prime matter has been rejected as incoherent since the Middle Ages: something with no properties whatever cannot be said to be there, and pure potentiality with no actuality is arguably a description of nothing. Modern physics is no comfort to either side - fields and particles are not stuff in the everyday sense, and the search for a fundamental material has repeatedly found structure instead.

Idealists take the whole notion to be a mistake. Berkeley's argument is that we have no idea of matter distinct from the sensible qualities, and that a substrate we cannot perceive, cannot conceive and do not need is a philosopher's invention. The counter-argument is not that his reasoning fails but that the conclusion is unbelievable, which is not the same thing.

Commonly confused with

physical stuff The everyday sense is what you can weigh. The philosophical term is what remains when you subtract the arrangement, and it is not obvious that anything does.
Substance c. 330 BC Substance is what has the properties. Matter is what a thing is made of, and on Aristotle's account a substance is form and matter together.
materia in physics Physics measures mass and energy. It does not answer, and does not try to answer, what the stuff is that has them.

Defined against

Form Neither term means anything without the other, which is why Aristotle never uses one alone

Philosophers

Aristotle Matter as potentiality, and always relative to a form
Democritus Atoms and void, with qualities as arrangement
Leucippus of Miletus The atomist hypothesis, in its first form
René Descartes Matter as extension and nothing else
George Berkeley The case that there is no such thing

Works

Metaphysics Form and matter, and the regress downward
On the Nature of Things Atomism in its most complete surviving statement
Meditations on First Philosophy Matter identified with extension
Three Dialogues between Hylas and Philonous The argument that matter is an idea we cannot form
Samkhya Karika Prakṛti as an active principle with qualities

Schools

Peripatetic school (Aristotelianism) Where matter is potentiality
Atomism Where it is particles and void
Cartesianism Where it is extension
British Empiricism Where it becomes an unknown support
Sāṃkhya school Where it is active rather than inert

Related concepts

Form c. 380 BC · Substance c. 330 BC · Qi c. 320 BC · Change c. 500 BC · Potentiality c. 330 BC

Aristotle's word is hulē, timber - the stuff a carpenter starts with - and the technical sense is built from that ordinary one.