Two days ago, as the United States celebrated the Martin Luther King, Jr. holiday, it occurred to me that King often gets praised for his civil-rights work, but little is said about his probing and intense preaching, which he considered his "first calling and greatest commitment."

Last year, I listened to A Knock at Midnight: Inspiration from the Sermons of Dr. Martin Luther King, Jr., an audio collection of eleven King sermons, each introduced by a key leader such as Wyatt Tee Walker or Billy Graham.

In the earliest sermon, "Rediscovering Lost Values" (1954), a very young King shows flashes of the oratorical brilliance that would come to maturity later. He retells the story of Mary and Joseph traveling home from Jerusalem only to find they have left behind something precious — Jesus. Thus they must go back before they can go forward. King uses that position as an analogy for the position of our society: though full of knowledge and scientific discovery, we must go back and rediscover ...