Institutio Oratoria

Another slander is to the effect that no art will acquiesce in false opinions: since an art must be based on direct perception, which is always true: now, say they, rhetoric does give its assent to false conclusions and is therefore not an art.

I will admit that rhetoric sometimes substitutes falsehood for truth, but I will not allow that it does so because its opinions are false, since there is all the difference between holding a certain opinion oneself and persuading someone else to adopt an opinion. For instance a general frequently makes use of falsehood: Hannibal when hemmed in by Fabius persuaded his enemy that he was in retreat by