thing to have been demonstrated. The orator's demonstration is an
enthymeme, and this is, in general, the most effective of the modes of
persuasion. The enthymeme is a sort of syllogism, and the
consideration of syllogisms of all kinds, without distinction, is
the business of dialectic, either of dialectic as a whole or of one of
its branches. It follows plainly, therefore, that he who is best
able to see how and from what elements a syllogism is produced will
also be best skilled in the enthymeme, when he has further learnt what
its subject-matter is and in what respects it differs from the
syllogism of strict logic. The true and the approximately true are
apprehended by the same faculty; it may also be noted that men have
a sufficient natural instinct for what is true, and usually do
arrive at the truth. Hence the man who makes a good guess at truth
is likely to make a good guess at probabilities.

  It has now been shown that the ordinary writers on rhetoric treat of
non-essentials; it has also been shown why they have inclined more
towards the forensic branch of oratory.

  Rhetoric is useful (1) because things that are true and things
that are just have a natural tendency to prevail over their opposites,
so that if the decisions of judges are not what they ought to be,
the defeat must be due to the speakers themselves, and they must be
blamed accordingly. Moreover, (2) before some audiences not even the
possession of the exactest knowledge will make it easy for what we say
to produce conviction. For argument based on knowledge implies
instruction, and there are people whom one cannot instruct. Here,
then, we must use, as our modes of persuasion and argument, notions
possessed by everybody, as we observed in the Topics when dealing with
the way to handle a popular audience. Further, (3) we must be able
to employ persuasion, just as strict reasoning can be employed, on
opposite sides of a question, not in order that we may in practice
employ it in both ways (for we must not make people believe what is
wrong), but in order that we may see clearly what the facts are, and
that, if another man argues unfairly, we on our part may be able to
confute him. No other of the arts draws opposite conclusions:
dialectic and rhetoric alone do this. Both these arts draw opposite
conclusions impartially. Nevertheless, the underlying facts do not
lend themselves equally well to the contrary views. No; things that
are true and things that are better are, by their nature,
practically always easier to prove and easier to believe in. Again,
(4) it is absurd to hold that a man ought to be ashamed of being
unable to defend himself with his limbs, but not of being unable to
defend himself with speech and reason, when the use of rational speech
is more distinctive of a human being than the use of his limbs. And if
it be objected that one who uses such power of speech unjustly might
do great harm, that is a charge which may be made in common against
all good things except virtue, and above all against the things that
are most useful, as strength, health, wealth, generalship. A man can
confer the greatest of benefits by a right use of these, and inflict
the greatest of injuries by using them wrongly.

  It is clear, then, that rhetoric is not bound up with a single
definite class of subjects, but is as universal as dialectic; it is
clear, also, that it is useful. It is clear, further, that its
function is not simply to succeed in persuading, but rather to
discover the means of coming as near such success as the circumstances
of each particular case allow. In this it resembles all other arts.
For example, it is not the function of medicine simply to make a man
quite healthy, but to put him as far as may be on the road to
health; it is possible to give excellent treatment even to those who
can never enjoy sound health. Furthermore, it is plain that it is
the function of one and the same art to discern the real and the
apparent means of persuasion, just as it is the function of
dialectic to discern the real and the apparent syllogism. What makes a
man a 'sophist' is not his faculty, but his moral purpose. In
rhetoric, however, the term 'rhetorician' may describe either the
speaker's knowledge of the art, or his moral purpose. In dialectic
it is different: a man is a 'sophist' because he has a certain kind of
moral purpose, a 'dialectician' in respect, not of his moral
purpose, but of his faculty.

  Let us now try to give some account of the systematic principles
of Rhetoric itself-of the right method and means of succeeding in
the object we set before us. We must make as it were a fresh start,
and before going further define what rhetoric is.

                                 2

  Rhetoric may be defined as the faculty of observing in any given
case the available means of persuasion. This is not a function of
any other art. Every other art can instruct or persuade about its
own particular subject-matter; for instance, medicine about what is
healthy and unhealthy, geometry about the properties of magnitudes,
arithmetic about numbers, and the same is true of the other arts and
sciences. But rhetoric we look upon as the power of observing the
means of persuasion on almost any subject presented to us; and that is
why we say that, in its technical character, it is not concerned
with any special or definite class of subjects.

  Of the modes of persuasion some belong strictly to the art of
rhetoric and some do not. By the latter I mean such things as are
not supplied by the speaker but are there at the outset-witnesses,
evidence given under torture, written contracts, and so on. By the
former I mean such as we can ourselves construct by means of the
principles of rhetoric. The one kind has merely to be used, the
other has to be invented.

  Of the modes of persuasion furnished by the spoken word there are
three kinds. The first kind depends on the personal character of the