Jacob Douvier claims that "Good rhetoric ought to appeal to good reason. Bad rhetoric rests on emotional manipulation."
Hmm, sounds too simplistic to me, and too mechanical. Here is how I responded to him.
While I agree in part I am uneasy about juxtaposing reason and emotion. True, you qualify it as manipulation, but would you go on to say that pure appeals to emotion are intrinsically manipulative? From what you say I would guess that you are more comfortable with Paul's letter to the Romans than with the extravagantly emotional Psalms of David or of Korah's sons.
I am glad that you use the word "reason" rather than "logic," but still I would maintain that good rhetoric is generally rife with emotion and with imagery. Its roots in the speaker and its fruit in the hearer lie more in the imagination than in logic.
No one ever made any great decision based on logic. Are you married? Did you marry because logic convinced you that it was in your best interest to marry, and to marry that particular woman? No, of course not. Your imagination carried you away as you played with all of the possibilities that such a marriage might open up.
So it is always: the imagination plays with possibilities and we find ourselves convinced of what we must do. Did Jesus appeal only to reason? Did he not paint word pictures of life and death, of life in the Kingdom, death without? And weren't these blatantly appeals to the listeners' imaginations and their emotions?
Of course, a wise imagination must be tutored by reason and accurate information. Imagination must study. Imagination without reason is folly. But reason alone will never make a decision, it will never be a hero, it will never bear children.Good rhetoric is reasonable, emotional, imaginative, honest and passionate.