Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
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.
Nor is this to be wondered at, since the term is also in common use among artists; hence the Vergilian phrase A mighty argument. [*](Aen. vii. 791, with Reference to the design on the shield of Turnus. ) Again a work which deals with a number of different themes is called
rich in argument.But the sense with which we are now concerned is that which provides proof Celsus indeed treats the terms, proof, indication, credibility, attempt, simply as different names for the same things, in which, to my thinking, he betrays a certain confusion of thought.
For proof and credibility are not merely the result of logical processes, but may equally be secured by inartificial arguments. Now I have already [*](v. ix. 2.) distinguished signs or, as he prefers to call them, indications from arguments. Consequently, since an argument is a process of reasoning
Otherwise there will be nothing by which we can prove anything; there must be something which either is or is believed to be true, by means of which doubtful things may be rendered credible. We may regard as certainties, first, those things which we perceive by the senses, things for instance that we hear or see, such as signs or indications; secondly, those things about which there is general agreement, such as the existence of the gods or the duty of loving one's parents;