But this real constitution, or (as it is apt to be called) essence, being utterly unknown to us, any sound that is put to stand for it must be very uncertain in its application; and it will be impossible to know what things are or ought to be called a HORSE, or ANTIMONY, when those words are put for real essences that we have no ideas of at all.

And therefore in this supposition, the names of substances being referred to standards that cannot be known, their significations can never be adjusted and established by those standards.
13.

Secondly, To co-existing Qualities, which are known but imperfectly.
Secondly, The simple ideas that are FOUND TO CO-EXIST IN SUBSTANCES being that which their names immediately signify, these, as united in the several sorts of things, are the proper standards to which their names are referred, and by which their significations may be best rectified.

But neither will these archetypes so well serve to this purpose as to leave these names without very various and uncertain significations.

Because these simple ideas that co-exist, and are united in the same subject, being very numerous, and having all an equal right to go into the complex specific idea which the specific name is to stand for, men, though they propose to themselves the very same subject to consider, yet frame very different ideas about it; and so the name they use for it unavoidably comes to have, in several men, very different significations.