It's one thing to have religious faith based on things that supposedly happened 1,500, or 2,100, or 5,000 years ago, and quite another when a man who died in 1844 is your major prophet.

The history of the Church of Jesus Christ of Latter-day Saints is brief and new, and that can make for trouble. PBS's four-hour documentary The Mormons doesn't shy away from that trouble. Nor, in its almost maddening even-handedness, does it dwell on it.

Devout Mormons and Mormon-doubters alike may be angry at the report, which means that it will have done its job: to inform viewers about one of the world's fastest-growing and most financially solvent religions, one that nonetheless appears bizarre to many outsiders.

"Mormonism is a movement that celebrates its history, and yet it seems to be quite afraid of its history," says Jon Butler, former Yale history department chair and a specialist in religion in America, in the documentary that airs tonight and tomorrow at 9 on WHYY TV12.

Several times when that history has caused problems for the church, elders have announced changes in doctrine, saying that they had had a religious experience or had actually consulted with God. The Mormons particularly highlights church shifts away from polygamy and official disdain of blacks.

Don't these convenient revelations "make it almost impossible to be a Mormon?" I asked Terryl Givens, professor of literature and religion at the University of Richmond.

"Well," he replied, "that depends on whether or not you think God is a pragmatist."

Givens, himself a Mormon, was part of a panel presented by Frontline and The American Experience, which collaborated on this PBS report, at January's Television Critics Association gathering in Los Angeles.

And his short answer can give anybody a foundation for understanding what Mormons believe, even if it's still hard to imagine how they could believe it.

"The Mormons . . . insist that history can be reconciled with theology, that God operates in real time, that he interacts with human beings on the basis of real political, social, and personal conditions and circumstances."

Filmmaker Helen Whitney, who made John Paul II: The Millennial Pope and Faith and Doubt at Ground Zero and won a Peabody Award for The Choice '96, about the 1996 presidential election, directed her work into neutral territory, little-charted land in a world where point-of-view documentaries are the norm.

Using grim wagon-train recreations and old-time drawings and photos, tonight's two hours traces the birth of the church, its immediate repression, the murder of founder Joseph Smith, and the tortuous journey of the faithful to the intimidating wilds of Utah.

Tomorrow, The Mormons examines how the Church of Jesus Christ of Latter-day Saints, with some advice from on high, has transformed its image in two generations from dire threat to the American family to the most family-friendly faith in town.

Whitney visits with fervent believers and folks who have been mistreated by the church for questioning dogma. Several Mormon elders, including church president Gordon B. Hinckley, get their say-so. And there's the usual compliment of talking-head journalists and professors, who are fascinating, but whose religious beliefs, in one of the documentary's few failures, go unidentified.

Professorial superstar Harold Bloom, a Jew, gets the second-to-last word in the report. "Religion rises inevitably from our apprehension of our own death," he says. "Of all the religions that I know, the one that most vehemently and persuasively defies and denies the reality of death is the original Mormonism of prophet, seer and revelator Joseph Smith."

At the January presentation, Givens called it "an extremely audacious theology."

Whitney's documentary is the opposite of audacious. No entertainment masterpiece, it is a peerless explainer, outlining just how the Mormon beliefs got to be so bold, and how they can be a pillar of strength for the righteous while seeming loony and threatening to those who don't buy in.

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Contact television critic Jonathan Storm privately at 215-854-5618 or jstorm@phillynews.com. Read his recent work at http://go.philly.com/jonathanstorm.