Smarmy, smirky and relentlessly self-congratulatory, Bill Maher might be the last person atheists would want to represent their position in public, except for one crucial fact. He is so very, very smart and funny.

Maher's antireligion documentary, "Religulous" (it rhymes with ridiculous), has numerous blasts of raucous humor amid passages that feel like a screed. Maher occasionally uses his prodigious powers of mockery against creationists, jihadis, divinely inspired gay-bashers and self-proclaimed saviors of every stripe. Mostly, though, he just asks everyday believers inconvenient questions, corrects their factual errors and allows them to make fools of themselves. Anyone affiliated with a Big Important Religion should brace for a sound thrashing. And that goes double for Scientologists.

The film is structured as a travelogue, following Maher on a pilgrimage from the Holy Land to Rome, London, Amsterdam, Salt Lake City and the Bible Belt. At every stop along the way, he asks true believers to explain the basis of their faith, quizzes scientists about their religious convictions (the vast majority identify themselves as atheists) and interviews apostates about why they have departed their former beliefs. Director Larry Charles revs up the momentum with frequent cuts to cheesy Biblical epics, outbursts of sectarian violence and, in the case of one high-living Latino evangelist, Brian DePalma's "Scarface."

In some cases, no jokes are needed. A tour through a creationist theme park shows dinosaurs coexisting with cavemen, including a model stegosaurus wearing a saddle. And the film offers a Comparative Religions 101 overview of stories that circulated around the Near East thousands of years earlier. The Egyptian god Horus; Mithra, a Persian god, and Krishna, the Indian god, all have biographies that overlap Christ's.

The film is unlikely to change many minds. If atheists had a choir, Maher would be preaching to it. The film has no taste for ambiguity, and it might have worked better if it at least glancingly noted religion's positive contributions. I'm not saying that the Sistine Chapel, Bach's "St. Matthew Passion" and Catholic Charities make up for the Crusades, but it's something. "Religulous" is at its most intriguing when Maher has nuanced discussions with a couple of priests. The Vatican astronomer eloquently explains why the Bible can't be used to teach science, and a good-humored retired priest says the scriptures are a valuable moral guidebook, but it doesn't matter because people are going to do what they're going to do anyway.

Maher drops the joking tone in the end. He argues that putting nuclear weapons in the hands of political leaders who are guided by ancient mythologies is unhealthy for the future of the human race. "Grow up or die," he warns. It's a stern conclusion to a rollicking sermon.