— 583 —
      §9. As there is no discoverable connexion between Fixedness, and
the Colour, Weight, and other simple Ideas of that nominal Essence of
Gold; so if we make our complex Idea of Gold, a Body yellow, fusible,
ductile, weighty, and fixed, we shall be at the same uncertainty con-
cerning Solubility in Aqua regia; and for the same reason. Since we can
never, from consideration of the Ideas themselves, with certainty
affirm or deny, of a Body, whose complex Idea is made up of yellow,
very weighty, ductile, fusible, and fixed, that it is soluble in Aqua
regia: And so on of the rest of its Qualities. I would gladly meet
with one general Affirmation, concerning any Quality of Gold, that
any one can certainly know is true. It will, no doubt, be presently
objected, Is not this an universal certain Proposition, All Gold is
malleable? To which I answer, It is a very certain Proposition, if
Malleableness be a part of the complex Idea the word Gold stands for.
But then here is nothing affirmed of Gold, but that that Sound stands
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 makes not a part of the specifick Essence the name
Gold stands for, ’tis plain, All Gold is Malleable, is not a certain
Proposition. Because let the complex Idea of Gold, be made up of
which soever 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, ’tis impossible we should perceive that connexion, unless we
could discover that which ties them together.
Locke Hum IV, 6, §9, p. 583