Full Idea
Locke has two forms of antiessentialism: that there are no natural kinds independently of our own minds; or (weaker) that in practice we classify things on the basis not of their real essences but of their observable properties.
Gist of Idea
There are no independent natural kinds - or our classifications have to be subjective
Source
report of John Locke (Essay Conc Human Understanding (2nd Ed) [1694]) by Nicholas Jolley - Leibniz and Locke on Essences
Book Reference
'Leibniz: Critical and Interpretive Essays', ed/tr. Hooker,Michael [Manchester 1982], p.199
A Reaction
Having recently read Locke, I felt that his real commitment was to the second one. He keeps coming back to the thought that there are real essences out there. It is only his empirical commitment that makes him feel the quest is hopeless.