Institutio Oratoria
Quintilian
Quintilian. Institutio Oratoria, Volume 1-4. Butler, Harold Edgeworth, translator. Cambridge, Mass; London: Harvard University Press, William Heinemann Ltd., 1920-1922.
It is eloquencethey say
that snatches criminals from the penalties of the law, eloquence that from time to time secures the condemnation of the innocent and leads deliberation astray, eloquence that stirs up not merely sedition and popular tumult, but wars beyond all expiation, and that is most effective when it makes falsehood prevail over the truth.
The comic poets even accuse Socrates of teaching how to make the worse cause seem the better, while Plato says that Gorgias and Tisias made similar professions.