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.
