Some years ago, a colleague of mine had his students pair off according to their views on a controversial issue, one student on one side of the issue and the other on the opposite. He gave the "persuader" five minutes to try to persuade the "persuadee" of his viewpoint. When the time was up, he asked the "persuaders" to raise their hands if they had persuaded their partner. Many hands went up. Then he asked the "persuadees" to raise their hands if they had indeed been persuaded. Many fewer hands went up.
He then asked the persuaders who incorrectly thought they had convinced their partners to tell what their strategy had been. Invariably, they said that they had been at their rhetorical best, using logic and evidence to make their case. He then asked the persuaders who had succeeded to explain their strategy. Almost invariably, they said that they had simply asked questions. Why do you think what you think? Have you ever thought differently? Do you remember when you thought that way? What kinds of evidence would persuade you? If you thought this particular fact was not a fact, would that change your mind?
Thanks to Daniel Bier, who did an excellent editing job.