Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
The same nature, however, is not to be found in those arts which have no connexion with virtue. Consequently, since there are two kinds of speech, the continuous which is called rhetoric, and the concise which is called dialectic (the relation between which was regarded by Zeno as being so intimate that he compared the latter to the closed fist, the former to the open hand), even the art of disputation will be a virtue. Consequently there can be no doubt about oratory whose nature is so much fairer and franker.
I should like, however, to consider the point more fully and explicitly by appealing to the actual work of oratory. For how will the orator succeed in panegyric unless he can distinguish between what is honourable and the reverse? How