Full Idea
Since the powers or qualities that are observable by us are not the real essence of that substance, but depend on it and flow from it, any collection whatsoever of these qualities cannot be the real essence of that thing.
Gist of Idea
The observable qualities are never the real essence, since they depend on real essence
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 2.31.13)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.383
A Reaction
Of triangles he says that we can observe the real essence. Oderberg defends the view that real essences are largely observable, but I take them to largely consist of hidden features.
Related Idea
Idea 12241 Essences are real, about being, knowable, definable and classifiable [Oderberg, by PG]