The Complete Aristotle (eng.)

Infallible Signs, and
Enthymemes resting on them, by showing in any way that they do not
form a valid logical proof: this, too, we see from the Analytics.
All we can do is to show that the fact alleged does not exist. If
there is no doubt that it does, and that it is an Infallible Sign,
refutation now becomes impossible: for this is equivalent to a
demonstration which is clear in every respect.
26
    Amplification and Depreciation are not an element of enthymeme.
By ‘an element of enthymeme’ I mean the same thing as a line of
enthymematic argument-a general class embracing a large number of
particular kinds of enthymeme. Amplification and Depreciation are
one kind of enthymeme, viz. the kind used to show that a thing is
great or small; just as there are other kinds used to show that a
thing is good or bad, just or unjust, and anything else of the
sort. All these things are the subject-matter of syllogisms and
enthymemes; none of these is the line of argument of an enthymeme;
no more, therefore, are Amplification and Depreciation. Nor are
Refutative Enthymemes a different species from Constructive. For it
is clear that refutation consists either in offering positive proof
or in raising an objection. In the first case we prove the opposite
of our adversary’s statements. Thus, if he shows that a thing has
happened, we show that it has not; if he shows that it has not
happened, we show that it has. This, then, could not be the
distinction if there were one, since the same means are employed by
both parties, enthymemes being adduced to show that the fact is or
is not so-and-so. An objection, on the other hand, is not an
enthymeme at all, as was said in the Topics, consists in stating
some accepted opinion from which it will be clear that our opponent
has not reasoned correctly or has made a false assumption.
    Three points must be studied in making a speech; and we have now
completed the account of (1) Examples, Maxims, Enthymemes, and in
general the thought-element the way to invent and refute arguments.
We have next to discuss (2) Style, and (3) Arrangement.

Rhetoric, Book III
    Translated by W. Rhys Roberts
<
    div id="book3" class="book">
1
    In making a speech one must study three points: first, the means
of producing persuasion; second, the style, or language, to be
used; third, the proper arrangement of the various parts of the
speech. We have already specified the sources of persuasion. We
have shown that these are three in number; what they are; and why
there are only these three: for we have shown that persuasion must
in every case be effected either (1) by working on the emotions of
the judges themselves, (2) by giving them the right impression of
the speakers’ character, or (3) by proving the truth of the
statements made.
    Enthymemes also have been described, and the sources from which
they should be derived; there being both special and general lines
of argument for enthymemes.
    Our next subject will be the style of expression. For it is not
enough to know what we ought to say; we must also say it as we
ought; much help is thus afforded towards producing the right
impression of a speech. The first question to receive attention was
naturally the one that comes first naturally-how persuasion can be
produced from the facts themselves. The second is how to set these
facts out in language. A third would be the proper method of
delivery; this is a thing that affects the success of a speech
greatly; but hitherto the subject has been neglected. Indeed, it
was long before it found a way into the arts of tragic drama and
epic recitation: at first poets acted their tragedies themselves.
It is plain that delivery has just as much to do with oratory as
with poetry. (In connexion with poetry, it has been studied by
Glaucon of Teos among others.) It is, essentially, a matter of the
right management of the voice to express the various emotions-of
speaking loudly, softly, or between the two; of high, low, or
intermediate pitch; of the various rhythms that suit various
subjects. These are the three things-volume of sound, modulation of
pitch, and rhythm-that a speaker bears in mind. It is those who do
bear them in mind who usually win prizes in the dramatic contests;
and just as in drama the actors now count for more than the poets,
so it is in the contests of public life, owing to the defects of
our political institutions. No systematic treatise upon the rules
of delivery has yet been composed; indeed, even the study