13. Ideas of substances are ektupa, and inadequate.
Secondly, the complex ideas of substances are ectypes, copies
too; but not perfect ones, not adequate: which is very evident to the mind, in that it plainly perceives, that
whatever collection of simple ideas it makes of any substance that exists, it cannot be sure that it exactly answers
all that are in that substance. Since, not having tried all the operations of all other substances upon it, and found all
the alterations it would receive from, or cause in, other substances, it cannot have an exact adequate collection of
all its active and passive capacities; and so not have an adequate complex idea of the powers of any substance
existing, and its relations; which is that sort of complex idea of substances we have. And, after all, if we would
have, and actually had, in our complex idea, an exact collection of all the secondary qualities or powers of any
substance, we should not yet thereby have an idea of the essence of that thing. For, since the powers or qualities
that are observable by us are not the real essence of that substance, but depend on it, and flow from it, any
collection whatsoever of these qualities cannot be the real essence of that thing. Whereby it is plain, that our ideas
of substances are not adequate; are not what the mind intends them to be. Besides, a man has no idea of substance
in general, nor knows what substance is in itself.
