What does the textbook mean when it says that a persuasive speech is a kind of mental dialogue between the speaker and the audience? Why is it important for you to keep this mental dialogue in mind when you prepare a persuasive speech?
Listeners do not passively soak in everything a speaker says. Rather, they engage in a mental give-and-take with the speaker. They actively assess the speaker's credibility, delivery, supporting materials, language, reasoning, and emotional appeals. They argue with the speaker inside their heads.
As a speaker, you need to anticipate the possible objections listeners might raise to your point of view. After anticipating possible objections, you must answer them in your speech. You cannot persuade skeptical listeners unless you deal directly with the reasons for their skepticism.