arm, at another cold, at one time good, at another bad. This
capacity is found nowhere else, though it might be maintained that a
statement or opinion was an exception to the rule. The same statement,
it is agreed, can be both true and false. For if the statement 'he is
sitting' is true, yet, when the person in question has risen, the same
statement will be false. The same applies to opinions. For if any one
thinks truly that a person is sitting, yet, when that person has risen,
this same opinion, if still held, will be false. Yet although this
exception may be allowed, there is, nevertheless, a difference in the
manner in which the thing takes place. It is by themselves changing
that substances admit contrary qualities. It is thus that that which
was hot becomes cold, for it has entered into a different state.
Similarly that which was white becomes black, and that which was bad
good, by a process of change; and in the same way in all other cases it
is by changing that substances are capable of admitting contrary
qualities. But statements and opinions themselves remain unaltered in
all respects: it is by the alteration in the facts of the case that the
contrary quality comes to be theirs. The statement 'he is sitting'
remains unaltered, but it is at one time true, at another false,
according to circumstances. What has been said of statements applies
also to opinions. Thus, in respect of the manner in which the thing
takes place, it is the peculiar mark of substance that it should be
capable of admitting contrary qualities; for it is by itself changing
that it does so.

If, then, a man should make this exception and contend that statements
and opinions are capable of admitting contrary qualities, his
contention is unsound. For statements and opinions are said to have
this capacity, not because they themselves undergo modification, but
because this modification occurs in the case of something else. The
truth or falsity of a statement depends on facts, and not on any power
on the part of the statement itself of admitting contrary qualities. In
short, there is nothing which can alter the nature of statements and
opinions. As, then, no change takes place in themselves, these cannot
be said to be capable of admitting contrary qualities.

But it is by reason of the modification which takes place within the
substance itself that a substance is said to be capable of admitting
contrary qualities; for a substance admits within it