If you are preaching or speaking to people who have strong doubts about the Bible, you should reinforce the points you are making from the biblical text with supporting material from sources that your listeners trust. Paul himself most famously does this in Acts 17.28 when he quotes the pagan writer, Aratus [ca. 315-240 BC, Greek poet], to an audience of pagan philosophers who would not otherwise grant the Bible any authority.
Many will balk at the idea of supplementing the Bible at all. Shouldn’t you simply preach the text itself and allow the Bible’s own authority to come through and convince people? The Bible, indeed, has a unique, divine, living power, a penetrating persuasiveness that issues from God Himself (Hebrews 4.12). Yet, to quote some other thinker is not fundamentally different from using illustrations out of daily life to reinforce the Bible’s teaching. No preacher simply reads the biblical assertions to people. All teachers and communicators deploy anecdotes, examples, stories, and other accounts that convince listeners and drive the biblical truths home.
If you are preaching on the First Commandment (“You shall have no other gods before me”) or Ephesians 5.5 (which calls greed idolatry) or any of the several hundred other places in the Bible that speak of idols, you could quote David Foster Wallace [1962-2008], the late post-modern [American] novelist. In his Kenyon College commencement speech, he argues eloquently and forcefully that “everyone worships. The only choice we get is what to worship.” He goes on to say everyone has to “tap real meaning in life,” and whatever you use to do that, whether it is money, beauty, power, intellect, or something else, it will drive your life because it is, essentially, a form of worship. He enumerates why each form of worship does not merely make you fragile and exhausted but can “eat you alive.” If you lay out his argument in support of fundamental biblical teaching, even the most secular audience will get quiet and keep listening to what you say next.
If you are teaching on moral absolutes – on any of the hundreds of biblical texts that say God’s Word has authority over human opinion and legislation – you could quote Martin Luther King, Jr. [1929-1968, American preacher and civil rights activist] with great effect. In his “Letter from Birmingham Jail,” he cites both Augustine and Thomas Aquinas to argue that human laws are only just when they square with “the moral law…the law of God…eternal law.” King’s personal example and argument are very disarming for secular listeners and almost guarantee consideration of your thesis.
From: Preaching: Communicating Faith in an Age of Skepticism by Timothy Keller (New York: Viking, 2015), pp. 106-108.
Timothy J. Keller (born in 1950) has pastored Redeemer Presbyterian Church (PCA) in New York, New York, since it was founded in 1989. He is a prolific author. Material in square brackets added by me.