osed to co-exist in nature, every one has a right to put into his
complex idea those qualities he has found to be united together. For,
though in the substance of gold one satisfies himself with colour and
weight, yet another thinks solubility in aqua regia as necessary to
be joined with that colour in his idea of gold, as any one does its
fusibility; solubility in aqua regia being a quality as constantly
joined with its colour and weight as fusibility or any other; others
put into it ductility or fixedness, &c., as they have been taught by
tradition or experience. Who of all these has established the right
signification of the word, gold? Or who shall be the judge to determine?
Each has his standard in nature, which he appeals to, and with reason
thinks he has the same right to put into his complex idea signified by
the word gold, those qualities, which, upon trial, he has found united;
as another who has not so well examined has to leave them out; or a
third, who has made other trials, has to put in others. For the union in
nature of these qualities being the true ground of their union in one
complex idea, who can say one of them has more reason to be put in or
left out than another? From hence it will unavoidably follow, that the
complex ideas of substances in men using the same names for them,
will be very various, and so the significations of those names very
uncertain.

14. Thirdly, To co-existing Qualities which are known but imperfectly.

Besides, there is scarce any particular thing existing, which, in some
of its simple ideas, does not communicate with a greater, and in others
a less number of particular beings: who shall determine in this case
which are those that are to make up the precise collection that is to
be signified by the specific name? or can with any just authority
prescribe, which obvious or common qualities are to be left out;
or which more secret, or more particular, are to be put into the
signification of the name of any substance? All which together, seldom
or never fail to produce that various and doubtful signification in
the names of substances, which causes such uncertainty, disputes, or
mistakes, when we come to a philosophical use of them.

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,