Nature sets the boundaries of the species of things: or, if it be so,
our boundaries of species are not exactly conformable to those in
nature. For we, having need of general names for present use, stay not
for a perfect discovery of all those qualities which would BEST show us
their most material differences and agreements; but we ourselves divide
them, by certain obvious appearances, into species, that we may the
easier under general names communicate our thoughts about them. For,
having no other knowledge of any substance but of the simple ideas that
are united in it; and observing several particular things to agree with
others in several of those simple ideas; we make that collection our
specific idea, and give it a general name; that in recording our
thoughts, and in our discourse with others, we may in one short word
designate all the individuals that agree in that complex idea, without
enumerating the simple ideas that make it up; and so not waste our time
and breath in tedious descriptions: which we see they are fain to do who
would discourse of any new sort of things they have not yet a name for.

31. Essences of Species under the same Name very different in different
minds.

But however these species of substances pass well enough in ordinary
conversation, it is plain that this complex idea wherein they observe
several individuals to agree, is by different men made very differently;
by some more, and others less accurately. In some, this complex idea
contains a greater, and in others a smaller number of qualities; and so
is apparently such as the mind makes it. The yellow shining colour makes
gold to children; others add weight, malleableness, and fusibility; and
others yet other qualities, which they find joined with that yellow
colour, as constantly as its weight and fusibility. For in all these and
the like qualities, one has as good a right to be put into the complex
idea of that substance wherein they are all joined as another. And
therefore different men, leaving out or putting in several simple ideas
which others do not, according to their various examination, skill, or
observation of that subject, have different essences of gold, which must
therefore be of their own and not of nature's making.

32. The more general our Ideas of Substances are, the more incomplete
and partial they are.

If the number of simple ideas that make the nominal essence of the
lowest species, or first sorting, of indivi