Full Idea
Aristotle shows that, for something to be a subject at all, it must be specifiable as something in itself, with essential properties that are mentioned in its defining account, since no subject can be the bearer of accidental properties alone.
Gist of Idea
To be a subject a thing must be specifiable, with some essential properties
Source
report of Aristotle (Metaphysics [c.324 BCE], Z.3) by Mary Louise Gill - Aristotle on Substance Ch.2
Book Reference
Gill,Mary Louise: 'Aristotle on Substance: Paradox of Unity' [Princeton 1989], p.41
A Reaction
This is Aristotle supporting the very modern necessary-properties view of essentialism. Notice that it emerges from being 'specifiable' - that is, from Aristotle's requirement that a logos and definition be available. He rejects bare particulars.