Full Idea
If anyone thinks that a man, a horse, an animal, a plant, are distinguished by real essences made by nature, he must think nature to be very liberal, making one for body, another for an animal, and another for a horse, all bestowed upon Bucephalus.
Clarification
Bucephalus was the horse of Alexander the Great
Gist of Idea
If every sort has its real essence, one horse, being many sorts, will have many essences
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 3.06.32)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.460
A Reaction
This is a powerful argument in favour of individual essences, and strongly against kind essences. Locke at his best, I would say.