Full Idea
We only suppose the being of real essences, without precisely knowing what they are: but that which annexes them still to the species is the nominal essence.
Gist of Idea
Real essences are unknown, so only the nominal essence connects things to a species
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 3.06.06)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.442
A Reaction
Compare Idea 12532. Locke can't quite make up his mind about the role of the 'sort' in our understanding of essence. His most consistent position is (I take it) to reject it entirely, as he did at first. ...Beginning of 3.06.07 confirms this.
Related Idea
Idea 12532 Even real essence depends on a sort, since it is sorts which have the properties [Locke]