The "Art" of Rhetoric (1.2.2-1.2.6)

As for proofs, some are artificial, others inartificial. By the latter I understand all those which have not been furnished by ourselves but were already in existence, such as witnesses, tortures, contracts, and the like; by the former, all that can be constructed by system and by our own efforts. Thus we have only to make use of the latter, whereas we must invent the former.

The orator persuades by moral character when his speech is delivered in such a manner as to render him worthy of confidence; for we feel confidence in a greater degree and more readily in persons of worth in regard to everything in general, but where there is no certainty and there is room for doubt, our confidence is absolute. But this confidence must be due to the speech itself, not to any preconceived idea of the speaker's character; for it is not the case, as some writers of rhetorical treatises lay down in their Art, that the worth of the orator in no way contributes to his powers of persuasion; on the contrary, moral character, so to say, constitutes the most effective means of proof.

The orator persuades by means of his hearers, when they are roused to emotion by his speech; for the judgements we deliver are not the same when we are influenced by joy or sorrow, love or hate; and it is to this alone that, as we have said, the present-day writers of treatises endeavor to devote their attention. (We will discuss these matters in detail when we come to speak of the emotions.)

Lastly, persuasion is produced by the speech itself, when we establish the true