Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
Others regard it not as an attempted or imperfect proof, but a complete proof, falling under the most special [*]( The last or lowest species. p. § 56 and VII. i. 23. ) species of proof; consequently, according to its proper and most generally received appellation it must be understood in the sense of a definite conception of some thought consisting of at least three parts. [*](i.e. the major and minor premisses and the conclusion. See v. xiv. 6 sqq. ) Some call an ἐπιχείρημα a reason,
but Cicero [*](de Inv. . xxxi. 34. ) is more correct in calling it a reasoning, although he too seems to derive this name from the syllogism rather than anything else; for he calls the syllogistic basis [*](See III. vi. 43, 46, 51.) a ratiocinative basis and quotes philosophers to support him. And since there is a certain kinship between a syllogism and an epicheireme, it may be thought that he was justified in his use of the latter term.
An ἀπόδεξις is a clear proof; hence the use of the term γραμμικαὶ ἀποδείξεις,
linear demonstrations[*](See I. x. 38.) by the geometricians. Caecilius holds that it differs from the epicheireme solely in the kind of conclusion arrived at and that an apodeixis is simply an incomplete epicheireme for the same reason that we said an enthymeme differed from a syllogism. For an epicheireme is also part of a syllogism. Some think that an apodeixis is portion of an epicheireme,
But all authorities, however much they may differ on other points, define both in the same way, in so far as they call both a method of proving what is not certain by means of what is certain. Indeed this is the nature of all arguments, for what is certain cannot be proved by what is uncertain. To all these forms of argument the Greeks give the name of πίστεις , a term which, though the literal translation is fides
a warrant of credibility,is best translated by probatio
proof.But argument has several other meanings.
For the plots of plays composed for acting in the theatre are called arguments, while Pedianus, when explaining the themes of the speeches of Cicero, says The argument is as follows. Cicero [*](In some letter now lost.) himself in writing to Brutus says, Fearing that I might transfer something from that source to my Cato, although the argument is quite different. It is thus clear that all subjects for writing are so called.