Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
Of those who divorce eloquence from that yet fairer and more desirable title to renown, a virtuous life, some call rhetoric merely a power, some a science, but not a virtue, some a practice, some an art, though they will not allow the art to have anything in common with science or virtue, while some again call it a perversion of art or κακοτεχνία.
These persons have as a rule held that the task of oratory lies in persuasion or speaking in a persuasive manner: for this is within the power of a bad man no less than a good. Hence we get the common definition of rhetoric as the power of persuading. What I call a power, many call a capacity, and some a faculty. In order therefore that there may be no misunderstanding I will say that by power I mean δύναμις.
This view is derived from Isocrates, if indeed the treatise on
worker of persuasion: for I cannot bring myself to use the peculiar derivative which Ennius [*](Ann. ix. 309 (Vahlen). The derivative to which he objects is the rare word suada. ) applies to Marcus Cethegus in the phrase suadae medulla, the
marrow of persuasion.