In the article that I referenced recently from Christian Century (“Stand and Deliver”), the author, Jason Byassee (the director of the Center for Theology, Writing & Media at Duke Divinity School) advocates that all speakers, Christian or not share three imperatives:
Cicero’s description of the three-part task of rhetoric applies equally to [preachers] and to secular performers: they seek to instruct, to delight and to move.
The citation is from De Optimo Genere Oratorum (“On the Best Style of Orators)
In The Mirror of Language: A Study in the Medieval Theory of Knowledge, (University of Nebraska Press, 1983) Marcia L. Colish expands on this:
The orator has three aims, “to prove, to please, to sway.” Of these three objectives, persuasion is the most important: “The supreme orator, then is the one whose speech instructs, delights, and moves the minds of the audience. The orator is duty bound to instruct, giving pleasure is a free gift to the audience; to move them is indispensable.
Colish’s quote/paraphrase is not quite accurate and I believe the difference is important. The original states that “to delight, is indispensably requisite to engage the attention.”
Too many sermons don’t take this aspect of public speaking seriously. That is why so many sermons are so deadly dull. To “delight” is important in that it helps our listeners WANT to keep attention.