9. Our knowledge of substances is to be improved, not by contemplation of abstract ideas, but only by experience.
In our search after the knowledge of substances, our want of ideas that are suitable to such a way of proceeding
obliges us to a quite different method. We advance not here, as in the other, (where our abstract ideas are real as
well as nominal essences,) by contemplating our ideas, and considering their relations and correspondences; that
helps us very little, for the reasons, that in another place we have at large set down. By which I think it is evident,
that substances afford matter of very little general knowledge; and the bare contemplation of their abstract ideas
will carry us but a very little way in the search of truth and certainty. What, then, are we to do for the
improvement of our knowledge in substantial beings? Here we are to take a quite contrary course: the want of
ideas of their real essences sends us from our own thoughts to the things themselves as they exist. Experience here
must teach me what reason cannot: and it is by trying alone, that I can certainly know, what other qualities
co-exist with those of my complex idea, v.g. whether that yellow, heavy, fusible body I call gold, be malleable, or
no; which experience (which way ever it prove in that particular body I examine) makes me not certain, that it is
so in all, or any other yellow, heavy, fusible bodies, but that which I have tried. Because it is no consequence one
way or the other from my complex idea: the necessity or inconsistence of malleability hath no visible connexion
with the combination of that colour, weight, and fusibility in any body. What I have said here of the nominal
essence of gold, supposed to consist of a body of such a determinate colour, weight, and fusibility, will hold true,
if malleableness, fixedness, and solubility in aqua regia be added to it. Our reasonings from these ideas will carry
us but a little way in the certain discovery of the other properties in those masses of matter wherein all these are to
be found. Because the other properties of such bodies, depending not on these, but on that unknown real essence
on which these also depend, we cannot by them discover the rest; we can go no further than the simple ideas of
our nominal essence will carry us, which is very little beyond themselves; and so afford us but very sparingly any
certain, universal, and useful truths. For, upon trial, having found that particular piece (and all others of that
colour, weight, and fusibility, that I ever tried) malleable, that also makes now, perhaps, a part of my complex
idea, part of my nominal essence of gold: whereby though I make my complex idea to which I affix the name
gold, to consist of more simple ideas than before; yet still, it not containing the real essence of any species of
bodies, it helps me not certainly to know (I say to know, perhaps it may be to conjecture) the other remaining
properties of that body, further than they have a visible connexion with some or all of the simple ideas that make
up my nominal essence. For example, I cannot be certain, from this complex idea, whether gold be fixed or no;
because, as before, there is no necessary connexion or inconsistence to be discovered betwixt a complex idea of a
body yellow, heavy, fusible, malleable; betwixt these, I say, and fixedness; so that I may certainly know, that in
whatsoever body these are found, there fixedness is sure to be. Here, again, for assurance, I must apply myself to
experience; as far as that reaches, I may have certain knowledge, but no further.
