ands for an idea in
which malleableness is contained: and such a sort of truth and certainty
as this it is, to say a centaur is four-footed. But if malleableness make
not a part of the specific essence the name of gold stands for, it is
plain, ALL GOLD IS MALLEABLE, is not a certain proposition. Because,
let the complex idea of gold be made up of whichsoever of its other
qualities you please, malleableness will not appear to depend on that
complex idea, nor follow from any simple one contained in it: the
connexion that malleableness has (if it has any) with those other
qualities being only by the intervention of the real constitution of its
insensible parts; which, since we know not, it is impossible we should
perceive that connexion, unless we could discover that which ties them
together.

10. As far as any such Co-existence can be known, so far Universal
Propositions maybe certain. But this will go but a little way.

The more, indeed, of these co-existing qualities we unite into one
complex idea, under one name, the more precise and determinate we make
the signification of that word; but never yet make it thereby more
capable of universal certainty, IN RESPECT OF OTHER QUALITIES NOT
CONTAINED IN OUR COMPLEX IDEA: since we perceive not their connexion or
dependence on one another; being ignorant both of that real constitution
in which they are all founded, and also how they flow from it. For the
chief part of our knowledge concerning substances is not, as in other
things, barely of the relation of two ideas that may exist separately;
but is of the necessary connexion and co-existence of several distinct
ideas in the same subject, or of their repugnancy so to co-exist. Could
we begin at the other end, and discover what it was wherein that colour
consisted, what made a body lighter or heavier, what texture of parts
made it malleable, fusible, and fixed, and fit to be dissolved in this
sort of liquor, and not in another;--if, I say, we had such an idea
as this of bodies, and could perceive wherein all sensible qualities
originally consist, and how they are produced; we might frame such
abstract ideas of them as would furnish us with matter of more general
knowledge, and enable us to make universal propositions, that should
carry general truth and certainty with them. But whilst our complex
ideas of the sorts of substances are so remote from that internal real
constitution on which their sensible qualities depend, and a