Full Idea
The kind that is common to both horse and ass and which most nearly comprises them happens not to have a name, but can safely be presumed to be both, i.e. the horse-ass or 'mule'. ...A mule does not come from a mule.
Gist of Idea
Unusual kinds like mule are just a combination of two kinds
Source
Aristotle (Metaphysics [c.324 BCE], 1033b32)
Book Reference
Aristotle: 'Metaphysics', ed/tr. Lawson-Tancred,Hugh [Penguin 1998], p.195
A Reaction
[second part at 1034b04] Does ancient Greek have a word for 'mule' - it sounds as if it doesn't. Nice chicken-and-egg problem. Must a natural kind be derived from a natural kind? No. Gold does not derive from gold.