— 477 —
Causes of their Imperfection.
      §5. Words having naturally no signification, the Idea which each
stands for, must be learned and retained by those, who would
exchange Thoughts, and hold intelligible Discourse with others, in
any Language. But this is hardest to be done, where,
      First, The Ideas they stand for, are very complex, and made up of a
great number of Ideas put together.
      Secondly, Where the Ideas they stand for, have no certain connex-
ion in Nature; and so no settled Standard, any where in Nature
existing, to rectify and adjust them by.
      Thirdly, Where the signification of the Word is referred to a
Standard, which Standard is not easy to be known.
      Fourthly, Where the signification of the Word, and the real
Essence of the Thing, are not exactly the same.
These are difficulties that attend the signification of several
Words that are intelligible. Those which are not intelligible at all,
such as Names standing for any simple Ideas, which another has not
Organs or Faculties to attain; as the Names of Colours to a blind
Man, or Sounds to a deaf Man, need not here be mentioned.
In all these cases, we shall find an imperfection in Words; which I
shall more at large explain, in their particular application to our
several sorts of Ideas: For if we examine them, we shall find, that the
Names of mixed Modes are most liable to doubtfulness and imperfection, for
the two first of these Reasons; and the Names of Substances chiefly for the two
latter.
Locke Hum III, 9, §5, p. 477