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.