5.  The only essences perceived by us in individual substances are those qualities which entitle them to receive their names.

Thus, if the idea of body with some people be bare extension or space, then solidity is not essential to body:  if others make the idea to which they give the name body to be solidity and extension, then solidity is essential to body.  That therefore, and that alone, is considered as essential, which makes a part of the complex idea the name of a sort stands for; without which no particular thing can be reckoned of that sort, nor be entitled to that name.  Should there be found a parcel of matter that had all the other qualities that are in iron, but wanted obedience to the loadstone, and would neither be drawn by it nor receive direction from it, would any one question whether it wanted anything essential?  It would be absurd to ask, Whether a thing really existing wanted anything essential to it.  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.  But essence, even in this sense, relates to A sort, and supposes A species.  For, being that real constitution on which the properties depend,