fusibility, fixedness, &c., which makes it to be gold, or gives it
a right to that name, which is therefore its nominal essence. Since
nothing can be called gold but what has a conformity of qualities to
that abstract complex idea to which that name is annexed. But this
distinction of essences, belonging particularly to substances, we shall,
when we come to consider their names, have an occasion to treat of more
fully.


19. Essences ingenerable and incorruptible.

That such abstract ideas, with names to them, as we have been speaking
of are essences, may further appear by what we are told concerning
essences, viz. that they are all ingenerable and incorruptible. Which
cannot be true of the real constitutions of things, which begin and
perish with them. All things that exist, besides their Author, are all
liable to change; especially those things we are acquainted with, and
have ranked into bands under distinct names or ensigns. Thus, that which
was grass to-day is to-morrow the flesh of a sheep; and, within a few
days after, becomes part of a man: in all which and the like changes,
it is evident their real essence--i. e. that constitution whereon the
properties of these several things depended--is destroyed, and perishes
with them. But essences being taken for ideas established in the mind,
with names annexed to them, they are supposed to remain steadily the
same, whatever mutations the particular substances are liable to. For,
whatever becomes of ALEXANDER and BUCEPHALUS, the ideas to which MAN and
HORSE are annexed, are supposed nevertheless to remain the same; and
so the essences of those species are preserved whole and undestroyed,
whatever changes happen to any or all of the individuals of those
species. By this means the essence of a species rests safe and entire,