20.  The Cause of this Abuse, a supposition of Nature’s working always regularly, in setting boundaries to Species.

That which I think very much disposes men to substitute their names for the real essences of species, is the supposition before mentioned, that nature works regularly in the production of things, and sets the boundaries to each of those species, by giving exactly the same real internal constitution to each individual which we rank under one general name.  Whereas any one who observes their different qualities can hardly doubt, that many of the individuals, called by the same name, are, in their internal constitution, as different one from another as several of those which are ranked under different specific names.  This supposition, however, that the same precise and internal constitution goes always with the same specific name, makes men forward to take those names for the representatives of those real essences; though indeed they signify nothing but the complex ideas they have in their minds when they use them.  So that, if I may so say, signifying one thing, and being supposed for, or put in the place of another, they cannot but, in such a kind of use, cause a great deal of uncertainty in men’s discourses; especially in those who have thoroughly imbibed the doctrine of substantial forms, whereby they firmly imagine the several species of things to be determined and distinguished.

21.  This Abuse contains two false Suppositions.

But however preposterous and absurd it be to make our names stand for ideas we have not, or (which is all one) essences that we know not, it being in effect to make our words the signs of nothing; yet it is evident to any one who ever so little reflects on the use men make of their words, that there is nothing more familiar.  When a man asks whether this or that thing he sees, let it be a drill, or a monstrous foetus, be a man or no; it is evident the question is not, Whether that particular thing agree to his complex idea expressed by the name man:  but whether it has in it the real essence of a species of things which he supposes his name man to stand for.  In which way of using the names of substances, there are these false suppositions contained:—­

First, that there are certain precise essences according to which nature makes all particular things, and by which they are distinguished into species.  That everything has a real constitution, whereby it is what it is, and on which its sensible qualities depend, is past doubt:  but I think it has been proved that this makes not the distinction of species as we rank them, nor the boundaries of their names.

Secondly, this tacitly also insinuates, as if we had ideas of these proposed essences.  For to what purpose else is it, to inquire whether this or that thing have the real essence of the species man, if we did not suppose that there were such a specifick essence known?  Which yet is utterly false.  And therefore such application of names as would make them stand for ideas which we have not, must needs cause great disorder in discourses and reasonings about them, and be a great inconvenience in our communication by words.