Opens: Oct. 3 (Lionsgate)

As a comedy routine about the absurdity of religious fundamentalism, Bill Maher's "Religulous" is very, very funny. As a serious discussion of religion and spirituality, the film is, well ... very, very funny. This film needs to come with the right consumer label such as "irreverent comedy" or "politically incorrect sermon." Anyone anticipating an in-depth look at how world religions go wrong or the failure of God in the modern age will be genuinely disappointed. As it stands, the film acts as a litmus test: If you love it, you're undoubtedly an agnostic secular humanist. If your blood boils, you're deeply religious.

Lionsgate will unveil the provocative film in Toronto following an almost secret Oscar qualifying run in New York and L.A. suburbs. The film will beckon non-believers in big cities before ascending to video heaven.

As a political humorist, Maher has never been afraid to offend. In fact, he seems to relish it. He just can't resist that final smart-alecky remark that skewers an opponent. Here, in his first major movie project, he travels the globe to discuss God and religion with true believers, challenging their interpretation of various holy scriptures and trying to understand -- or at least pretending to try -- what underlies fervent faith absent any proof of God's existence.

For the second movie in a row, director Larry Charles has made certain his cameras are in the right places and let his "lead actor" run away with the show. And like Sacha Baron Cohen in "Borat," Maher absorbs the limelight as a baby does his lotion.

Maher begins with a family revelation: He grew up Catholic yet his mother never went to church. Turns out she is Jewish. Of course, the family left Catholicism long ago -- something to do with birth control, she thinks -- so this now leaves Maher in the strong position to attack the entire Judeo-Christian ethos without any implication of bigotry.

He does a good job. The jealous, wrathful God of the Old Testament, the Virgin Birth of Jesus and concept of Original Sin -- the latter not in the Bible, Mayer points out -- are ridiculed. Clips from old movies illustrate the fallacy of literal interpretations of Bible stories. The Mormon belief that Indians represent a "lost tribe of Israel" juxtaposed with Mel Brooks' Yiddish-talking natives from "Blazing Saddles" is particularly effective.

The problem, if you're going to take Maher's inquiry seriously, is whom he chooses to question and where he chooses to go. For the most part, he verbally jousts with evangelical charlatans and red-neck whack jobs. He visits a Holy Land theme park and a Creationist museum.

Maher doesn't risk questioning a learned theologian or even a devote Christian or Jew who reads the holy scriptures as a spiritual guide without having to accept as literal truth stories written by men 2,000 years ago. William F. Buckley was still alive when this movie was made. Wouldn't you like to see Maher take on him? Nor does Maher acknowledge the deep divisions within many religions over issues such as homosexuality.

Maher does encounter an old priest outside the Vatican who seems to share his skepticism about literalism and jokes about how Italians have turned Catholicism into a polytheistic religion. At least the man says he's a priest. Guess we have to take that on faith.

Weirdly, Eastern religions get a pass. Maher spends a few minutes condemning Islamic jihadists and suicide bombers, but never mentions Buddhists, Sikhs or Hindus. Perhaps Hinduism with its million gods overwhelms his comic urges. Ditto that for native religions of the Americas or Africa.

Maher reserves his sharpest and most passionate outrage for politicians who wear religion on their sleeves like Boy Scout merit badges. An interview with Senator Mark Pryor (D-Ark.) certainly makes his point, more than the Senator may have realized.

But by focusing so narrowly on religious fundamentalists and bigots while ignoring any spiritual dimension to religion, the film is not only being disingenuous but limits its audience to non-believers. The fact remains, Maher is preaching to the choir.

Production companies: A Thousand Words/Bill Maher production. Director: Larry Charles. Producers: Bill Maher, Jonah Smith, Palmer West. Executive producer: Charlie Siskel, Jesse Johnston. Director of photography: Anthony Hardwick. Editors: Jeff Groth, Christian Kinnard, Jeffrey M. Werner. Rated R, 101 minutes.