, SPECIES, as essentially different as
any two of the most remote or opposite in the world.

15. Several significations of the word Essence.

But since the essences of things are thought by some (and not without
reason) to be wholly unknown, it may not be amiss to consider the
several significations of the word ESSENCE.

Real essences.

First, Essence may be taken for the very being of anything, whereby it
is what it is. And thus the real internal, but generally (in substances)
unknown constitution of things, whereon their discoverable qualities
depend, may be called their essence. This is the proper original
signification of the word, as is evident from the formation of it;
essential in its primary notation, signifying properly, being. And in
this sense it is still used, when we speak of the essence of PARTICULAR
things, without giving them any name.

Nominal Essences.

Secondly, The learning and disputes of the schools having been much
busied about genus and species, the word essence has almost lost its
primary signification: and, instead of the real constitution of things,
has been almost wholly applied to the artificial constitution of
genus and species. It is true, there is ordinarily supposed a real
constitution of the sorts of things; and it is past doubt there must
be some real constitution, on which any collection of simple ideas
co-existing must depend. But, it being evident that things are ranked
under names into sorts or species, only as they agree to certain
abstract ideas, to which we have annexed those names, the essence of
each GENUS, or sort, comes to be nothing but that abstract idea which
the general, or sortal (if I may have leave so to call it from sort, as
I do general from genus,) name stands for. And this we shall find to be
that which the word essence imports in its most familiar use.

These two sorts of essences, I suppose, may not unfitly be termed, the
one the REAL, the other NOMINAL ESSENCE.

16. Constant Connexion between the Name and nominal Essence.

Between the NOMINAL ESSENCE and the NAME there is so near a connexion,
that the name of any sort of things cannot be attributed to any
particular being but what has this essence, whereby it answers that
abstract idea whereof that name is the sign.

17. Supposition, that Species are distinguished by their real Essences
useless.

Concerning the REAL ESSENCES of corporeal substances (to mention these
only) there are, if I mis