Full Idea
It is as impossible that two things, partaking exactly of the same real essence, should have different properties, as that two figures partaking in the same real essence of a circle, should have different properties.
Gist of Idea
It is impossible for two things with the same real essence to differ in properties
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 3.03.17)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.418
A Reaction
Two circles could be of relatively different size, so we deduce from that that size is not essential. Hence essence of gold seems to be defined as those respects in which two samples of gold never vary. But that might be superficial…