CHAPEL HILL, N.C. Where does faith reside? In the soul? The mind, the marrow of the bones?

In the long hours of the night, the voices of the evangelical preachers on the AM dial seem to know. Believe, they say. Then daylight comes and the listeners' questions fade.

Bart Ehrman is a sermon, a parable, but of what? He's a best-selling author, a New Testament expert and perhaps a cautionary tale: the fundamentalist scholar who peered so hard into the origins of Christianity that he lost his faith altogether.

Once he was a seminarian and graduate of the Moody Bible Institute, a pillar of conservative Christianity. Its doctrine states that the Bible "is a divine revelation, the original autographs of which were verbally inspired by the Holy Spirit."

But after three decades of research into that divine revelation, Ehrman became an agnostic. What he found in the ancient papyri of the scriptorium was not the greatest story ever told, but the crumbling dust of his own faith.

"Sometimes Christian apologists say there are only three options to who Jesus was: a liar, a lunatic or the Lord," he tells a packed auditorium here at the University of North Carolina, where he chairs the department of religious studies. "But there could be a fourth option -- legend."

Ehrman's latest book, "Misquoting Jesus: The Story Behind Who Changed the Bible and Why," has become one of the unlikeliest bestsellers of the year. A slender book of textual criticism, currently at No. 16 on the New York Times bestseller list, it casts doubt on any number of New Testament episodes that most Christians take as, well, gospel.

Example: A crowd readies itself to stone an adulterous woman to death. Jesus leans down, doodles in the dust. Says, let the one without sin cast the first stone. The crowd melts away. It's one of the most famous stories in the Bible.

And it's most likely fiction, says Ehrman, seconding other scholars who say scribes added the episode to the biblical canon centuries after the life of Christ.

There are dozens of other examples in "Misquoting Jesus," things that go to the heart of the faith, things that have puzzled scholars for centuries. What actually happened to Jesus of Nazareth, there on the sands of Judea? Was he a small-time Jewish revolutionary or the Son of God? Both? Neither?

These ancient questions have been the guideposts to Ehrman's life. His take on them -- first as devout believer in biblical inerrancy, then as a skeptic who rejects it all -- suggests a demand for black and white in an arena where others see faith, mystery and the far traces of the unknowable.

"I think Bart is writing about his personal journey, about legitimate things that bother him," says Darrell Bock, research professor of New Testament studies at the Dallas Theological Seminary. Like many Christian scholars who have studied the ancient scrolls, Bock says his faith was strengthened by the same process that destroyed Ehrman's.