Nevertheless, Rhetoric is useful, because the true and the just are
naturally superior to their opposites, so that, if decisions are improperly
made, they must owe their defeat to their own advocates; which is reprehensible.
Further, in dealing with certain persons, even if we possessed the most accurate
scientific knowledge, we should not find it easy to persuade them by the
employment of such knowledge. For scientific discourse is concerned with
but in the case of such
persons instruction is impossible; our proofs and arguments must rest on
generally accepted principles, as we said in the Topics
when speaking of converse with the multitude. Further, the orator should be able
to prove opposites, as in logical arguments; not that we should do both
（for one ought not to persuade people to do what is wrong）,
but that the real state of the case may not escape us, and that we ourselves may
be able to counteract false arguments, if another makes an unfair use of them.
Rhetoric and Dialectic alone of all the arts prove opposites; for both are
equally concerned with them. However, it is not the same with the subject
matter, but, generally speaking, that which is true and better is naturally
always easier to prove and more likely to persuade. Besides, it would be absurd
if it were considered disgraceful not to be able to defend oneself with the help
of the body,
disgraceful as far as speech is concerned, whose use is more characteristic of
man than that of the body.