And if this be so, it is plain that OUR DISTINCT SPECIES are NOTHING BUT DISTINCT COMPLEX IDEAS, WITH DISTINCT NAMES ANNEXED TO THEM.

It is true every substance that exists has its peculiar constitution, whereon depend those sensible qualities and powers we observe in it; but the ranking of things into species (which is nothing but sorting them under several titles) is done by us according to the ideas that WE have of them: which, though sufficient to distinguish them by names, so that we may be able to discourse of them when we have them not present before us; yet if we suppose it to be done by their real internal constitutions, and that things existing are distinguished by nature into species, by real essences, according as we distinguish them into species by names, we shall be liable to great mistakes.
14.

Difficulties in the supposition of a certain number of real Essences To distinguish substantial beings into species, according to the usual supposition, that there are certain precise essences or forms of things, whereby all the individuals existing are, by nature distinguished into species, these things are necessary:-- 15.

A crude supposition.
First, To be assured that nature, in the production of things, always designs them to partake of certain regulated established essences, which are to be the models of all things to be produced.

This, in that crude sense it is usually proposed, would need some better explication, before it can fully be assented to.
16.