— 519 —
The Ideas of their Powers best by Definition.
      §22. But because many of the simple Ideas that make up our
specifick Ideas of Substances, are Powers, which lie not obvious to
— 520 —
our Senses in the Things as they ordinarily appear; therefore, in the
signification of our Names of Substances, some part of the signification will
be better made known, by enumerating those simple Ideas, than in shewing
the Substance it self. For he that, to the yellow shining Colour of Gold
got by sight, shall, from my enumerating them, have the Ideas of
great Ductility, Fusibility, Fixedness, and Solubility, in Aqua Regia,
will have a perfecter Idea of Gold, than he can have by seeing a piece
of Gold, and thereby imprinting in his Mind only its obvious Quali-
ties. But if the formal Constitution of this shining, heavy, ductil
Thing (from whence all these its Properties flow) lay open to our
Senses, as the formal Constitution, or Essence of a Triangle does,
the signification of the word Gold, might as easily be ascertained, as
that of Triangle.
Locke Hum III, 11, §22, pp. 519-520