Full Idea
The differentia, being generic in character, should be ranged with the genus.
Gist of Idea
Differentia are generic, and belong with genus
Source
Aristotle (Topics [c.331 BCE], 101b18)
Book Reference
Aristotle: 'Posterior Analytics and Topica', ed/tr. Tredennick,H/Forster,ES [Harvard 1960], p.279
A Reaction
This does not mean that naming the differentia amounts to mere classification. I presume we can only state individual differences by using a language which is crammed full of universals.