BOB ABERNETHY: If mainline Protestants could have elected a pope anytime over the last generation or so, that person would almost certainly have been Martin Marty, who retired this spring from the University of Chicago Divinity School, just a few weeks after turning 70. Our profile is from Kate Olsen of the NEWSHOUR.

Offscreen Voice: Who is Martin Marty?

KATE OLSEN: Five hundred people turned out to celebrate the 70th birthday of church historian Martin Marty and his retirement from the University of Chicago. The guests were entertained by a video about the man who for decades has been one of the nation's most influential religious thinkers. Public television commentator Bill Moyers reflected on Marty's legendary ability to turn out scholarly works on a dime.

BILL MOYERS: But the fact of the matter is, no one knows how many books Marty has written, including Marty. Many of his works have been published under the pseudonym ENCYCLOPEDIA BRITANNICA.

OLSEN: Writing with his favorite jazz or classical music in the background, Marty has produced some 50 books on religion and articles by the thousands, in both popular and academic publications. Many of them explain the diversity of American religion.

MARTIN MARTY: In any university classroom, in any subway, in any ball game, you might well have every religion ever known in ancient Greece, Rome, Egypt, and the yellow pages of today's phone book.

OLSEN: Marty has sometimes been criticized for his liberalism. But evangelical church historian Mark Knoll of Wheaton College says there's no religious spokesman quite like him.

MARK KNOLL (Wheaton College): Unlike some other well-known religious figures, Pat Robertson, Oral Roberts, Billy Graham, Marty is known for providing background, for providing context, for providing analysis, whereas these other well-known figures are known for promoting their particular view of religious matters.

The fact that Marty can do these things, can provide analysis to many different sources while clearly remaining obviously himself a person of faith, is remarkable.

OLSEN: Marty seems to be just about everywhere -- teaching in Chicago; studying the impact of religion on health; traveling around the country to explore religion where it's practiced; writing columns and reviews; responding to endless requests from the media; and, with musician wife Harriet, entertaining students at home.

He's booked two years ahead and scheduled to a minute, using every spare moment of his time. At his birthday dinner, his colleagues used one word to describe him.

Unidentified Woman #1: If I could describe Marty in one word it would definitely be "energy."

Unidentified Woman #2: "Energetic."

Unidentified Woman #3: "Energy."

Unidentified Woman #4: "Energy."

Unidentified Man: "Energy" really is not enough by itself.

Woman #4: "High energy."

OLSEN: One secret to his high energy is the seven-minute naps he takes several times a day, wherever he might be. He says it helps him live in the present and not be burdened with the past or worried about the future.

Mr. MARTY: I've always been moved at the heart of the Lord's Prayer. It says, "Give us this day our daily bread." And the Sermon on the Mount, "Don't take thought for tomorrow." These are part of the announcements of the kingdom. They are announcements that tell us that the one who created us doesn't take care of everything that will ever happen to us. But we get strength for the day we're in. And a nap frees me for that.