Or could it be demanded, Whether this made an essential or specific difference or no, since WE have no other measure of essential or specific but our abstract ideas?
And to talk of specific differences in NATURE, without reference to general ideas in names, is to talk unintelligibly.

For I would ask any one, What is sufficient to make an essential difference in nature between any two particular beings, without any regard had to some abstract idea, which is looked upon as the essence and standard of a species?
All such patterns and standards being quite laid aside, particular beings, considered barely in themselves, will be found to have all their qualities equally essential; and everything in each individual will be essential to it; or, which is more, nothing at all.

For, though it may be reasonable to ask, Whether obeying the magnet be essential to iron?
yet I think it is very improper and insignificant to ask, whether it be essential to the particular parcel of matter I cut my pen with; without considering it under the name IRON, or as being of a certain species.
And if, as has been said, our abstract ideas, which have names annexed to them, are the boundaries of species, nothing can be essential but what is contained in those ideas.
6.

Even the real essences of individual substances imply potential sorts.
It is true, I have often mentioned a REAL ESSENCE, distinct in substances from those abstract ideas of them, which I call their nominal essence.

By this real essence I mean, that real constitution of anything, which is the foundation of all those properties that are combined in, and are constantly found to co-exist with the nominal essence; that particular constitution which everything has within itself, without any relation to anything without it.