be predicated of the same Subject "in the same relation"; that is, at
the same time or place, or under the same conditions. The lamp is
visible to me now, but will be invisible if I turn it out; one side of
it is now visible, but the other is not: therefore without this
restriction, "in the same relation," few or no terms would be
contradictory.

If a man is called wise, it may mean 'on the whole' or 'in a certain
action'; and clearly a man may for once be wise (or act wisely) who, on
the whole, is not-wise. So that here again, by this ambiguity, terms
that seem contradictory are predicable of the same subject, but not "in
the same relation." In order to avoid the ambiguity, however, we have
only to construct the term so as to express the relation, as 'wise on
the whole'; and this immediately generates the contradictory 'not-wise
on the whole.' Similarly, at one age a man may have black hair, at
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