The measure and boundary of each sort or species, whereby it is
constituted that particular sort, and distinguished from others, is that
we call its ESSENCE, which is nothing but that abstract idea to which
the name is annexed; so that everything contained in that idea is
essential to that sort. This, though it be all the essence of natural
substances that WE know, or by which we distinguish them into sorts, yet
I call it by a peculiar name, the NOMINAL ESSENCE, to distinguish it
from the real constitution of substances, upon which depends this
nominal essence, and all the properties of that sort; which, therefore,
as has been said, may be called the REAL ESSENCE: v.g. the nominal
essence of gold is that complex idea the word gold stands for, let
it be, for instance, a body yellow, of a certain weight, malleable,
fusible, and fixed. But the real essence is the constitution of the
insensible parts of that body, on which those qualities and all the
other properties of gold depend. How far these two are different, though
they are both called essence, is obvious at first sight to discover.


3. The nominal and real Essence different.

For, though perhaps voluntary motion, with sense and reason, joined to a
body of a certain shape, be the complex idea to which I and others annex
the name MAN, and so be the nominal essence of the species so called:
yet nobody will say that complex idea is the real essence and source of
all those operations which are to be found in any individual of that
sort. The foundation of all those qualities which are the ingredients
of our complex idea, is something quite different: and had we such a
knowledge of that constitution of man; from which his faculties of
moving, sensation, and reasoning, and other powers flow, and on which
his so regular shape depends, as it is possible angels have, and it is