Full Idea
Talk of specific differences without reference to general ideas is unintelligible. What is sufficient to make an essential difference between two particular beings without a standard of the species? Particulars alone will have all qualities essentially.
Gist of Idea
You can't distinguish individuals without the species as a standard
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], 3.06.05)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.441
A Reaction
[compressed] The last idea is now called 'superessentialism'. I don't actually understand this. Can you not distinguish between two cats before you have classified them as 'cats', and invoked generalities about cats? Just list their features.