7.  Because men know not the real essence of substances.

Now, then, when men apply to this particular parcel of matter on my finger a general name already in use, and denominate it gold, do they not ordinarily, or are they not understood to give it that name, as belonging to a particular species of bodies, having a real internal essence; by having of which essence this particular substance comes to be of that species, and to be called by that name?  If it be so, as it is plain it is, the name by which things are marked as having that essence must be referred primarily to that essence; and consequently the idea to which that name is given must be referred also to that essence, and be intended to represent it.  Which essence, since they who so use the names know not, their ideas of substances must be all inadequate in that respect, as not containing in them that real essence which the mind intends they should.

8.  Ideas of Substances, when regarded as Collections of their Qualities, are all inadequate.

Secondly, those who, neglecting that useless supposition of unknown real essences, whereby they are distinguished, endeavour to copy the substances that exist in the world, by putting together the ideas of those sensible qualities which are found co-existing in them, though they come much nearer a likeness of them than those who imagine they know not what real specific essences:  yet they arrive not at perfectly adequate ideas of those substances they would thus copy into their minds:  nor do those copies exactly and fully contain all that is to be found in their archetypes.  Because those qualities and powers of substances, whereof we make their complex ideas, are so many and various, that no man’s complex idea contains them all.  That our complex ideas of substances do not contain in them all the simple ideas that are united in the things themselves is evident, in that men do rarely put into their complex idea of any substance all the simple ideas they do know to exist in it.  Because, endeavouring to make the signification of their names as clear and as little cumbersome as they can, they make their specific ideas of the sorts of substance, for the most part, of a few of those simple ideas which are to be found in them:  but these having no original precedency, or right to be put in, and make the specific idea, more than others that are left out, it is plain that both these ways our ideas of substances are deficient and inadequate.  The simple ideas whereof we make our complex ones of substances are all of them (bating only the figure and bulk of some sorts) powers; which being relations to other substances, we can never be sure that we know all the powers that are in any one body, till we have tried what changes it is fitted to give to or receive from other substances in their several ways of application:  which being impossible to be tried upon any one body, much less upon all, it is impossible we should have adequate ideas of any substance made up of a collection of all its properties.