15. With this imperfection, they may serve for civil, but not well for philosophical use.
It is true, as to civil and
common conversation, the general names of substances, regulated in their ordinary signification by some obvious
qualities, (as by the shape and figure in things of known seminal propagation, and in other substances, for the
most part by colour, joined with some other sensible qualities), do well enough to design the things men would be
understood to speak of: and so they usually conceive well enough the substances meant by the word gold or apple,
to distinguish the one from the other. But in philosophical inquiries and debates, where general truths are to be
established, and consequences drawn from positions laid down, there the precise signification of the names of
substances will be found not only not to be well established, but also very hard to be so. For example: he that shall
make malleability, or a certain degree of fixedness, a part of his complex idea of gold, may make propositions
concerning gold, and draw consequences from them, that will truly and clearly follow from gold, taken in such a
signification: but yet such as another man can never be forced to admit, nor be convinced of their truth, who
makes not malleableness, or the same degree of fixedness, part of that complex idea that the name gold, in his use
of it, stands for.
