another not-black hair; but the difficulty is practically removable by
stating the age referred to.

Still, this case easily leads us to a real difficulty in the use of
contradictory terms, a difficulty arising from the continuous change or
'flux' of natural phenomena. If things are continually changing, it may
be urged that contradictory terms are always applicable to the same
subject, at least as fast as we can utter them: for if we have just said
that a man's hair is black, since (like everything else) his hair is
changing, it must now be not-black, though (to be sure) it may still
seem black. The difficulty, such as it is, lies in this, that the human
mind and its instrument language are not equal to the subtlety of
Nature. All things flow, but the terms of human discourse assume a
certain fixity of things; everything at every moment changes, but for
the most part we can neither perceive this change nor express it in
ordinary language.

This paradox, however, may, I suppose, be easily over-stated. The change
that continually agitates Nature consists in the movements of masses or
molecules, and such movements of things are compatible with a
considerable persistence of their qualities. Not only are the molecular
changes always going on in a piece of gold compatible with its remaining
yellow, but its persistent yellowness depends on the continuance of some
of those changes. Similarly, a man's hair may remain black for some
years; though, no doubt, at a certain age its colour may begin to be
problematical, and the applicability to it of 'black' or 'not-black' may
become a matter of genuine anxiety. Whilst being on our guard, then,
against fallacies of contradiction arising from the imperfect
correspondence of fact with thought and language, we shall often have to
put up with it. Candour and humility having been satisfied by the above
acknowledgment of the subtlety of Nature, we may henceforward proceed
upon the postulate--that it is possible to use contradictory terms such
as cannot both be predicated of the same subject in the same relation,
though one of them may be; that, for example, it may be truly said of a
man for some years that his hair is black; and, if so, that during those
years to call it not-black is false or extremely misleading.

The most opposed terms of the literary vocabulary, however, such as
'wise-foolish,' 'old-young,' 'sweet-bitter,' are rarely true
contradictories: wise and foolish, indeed, c