Full Idea
If a speech is to be classed as excellent, does that not presuppose knowledge of the truth about the subject of the speech in the mind of the speaker.
Gist of Idea
An excellent speech seems to imply a knowledge of the truth in the mind of the speaker
Source
Plato (Phaedrus [c.368 BCE], 259e)
Book Reference
Plato: 'Phaedrus and Letters VII and VIII', ed/tr. Hamilton,Walter [Penguin 1973], p.71
A Reaction
I like the thought that Plato's main interest was rhetoric, but with the view that the only good rhetoric is truth-speaking. It would be hard to admire a speech if you disagreed with it.