An Essay Concerning Humane Understanding, Volume II. | Page 9

that, in truth, every distinct abstract idea is a
distinct essence; and the names that stand for such distinct ideas are the
names of things essentially different. Thus a circle is as essentially
different from an oval as a sheep from a goat; and rain is as essentially

different from snow as water from earth: that abstract idea which is the
essence of one being impossible to be communicated to the other. And
thus any two abstract ideas, that in any part vary one from another, with
two distinct names annexed to them, constitute two distinct sorts, or, if
you please, 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 mistake not, two opinions. The one is of those
who, using the word essence for they know not what, suppose a certain
number of those essences, according to which all natural things are
made, and wherein they do exactly every one of them partake, and so
become of this or that species. The other and more rational opinion is
of those who look on all natural things to have a real, but unknown,
constitution of their insensible parts; from which flow those sensible
qualities which serve us to distinguish them one from another,
according as we have occasion to rank them into sorts, under common
denominations. The former of these opinions, which supposes these
essences as a certain number of forms or moulds, wherein all natural
things that exist are cast, and do equally partake, has, I imagine, very
much perplexed the knowledge of natural things. The frequent
productions of monsters, in all the species of animals, and of
changelings, and other strange issues of human birth, carry with them
difficulties, not possible to consist with this hypothesis; since it is as
impossible that two things partaking exactly of the same real essence
should have different properties, as that two figures partaking of the
same real essence of a circle should have different properties. But were
there no other reason against it, yet the supposition of essences that
cannot be known; and the making of them, nevertheless, to be that

which distinguishes the species of things, is so wholly useless and
unserviceable to any part of our knowledge, that that alone were
sufficient to make us lay it by, and content ourselves with such
essences of the sorts or species of things as come within the reach