EW YORK — Striding into Washington Square Park with a fistful of photocopied circulars and an earnest expression, Eric Williams could have been an environmental canvasser or a hip missionary. In fact, he is a pastry chef — or was until last week, when he quit his job to devote himself full time to proving that the World Trade Center attack was ordered not by terrorists but by officials in the U.S. government.

Williams approached a pushcart vendor from Bangladesh: "Do you believe the official story, that Osama bin Laden and 19 hijackers took down the towers?"

"Yes," said the vendor.

Williams moved on to a Dominican woman. "Do you believe the government allowed the attacks to happen?"

The woman smiled, baffled, and asked her 10-year-old daughter to translate. "Do you believe Bin Laden was responsible for the attacks?" he asked the girl. The child shrugged expressively.

But he hit pay dirt with Nikolaos Vitoroulis, a freshman engineering student at Stevens Institute of Technology who was in the eighth grade at the time of the attacks. Vitoroulis, 18, said he had never believed a fire could cause a building to collapse that way, into its own footprint. The hijacked-plane scenario, he said, "seems a little fishy."

As New York readied for another anniversary of the Sept. 11 attacks, conspiracy theorists and researchers who belong to a group known as the 9/11 Truth Movement gathered in Greenwich Village. Among them were proponents of the "LIHOP" theory, who believe that members of the government "let it happen on purpose," and the "MIHOP" theory, who hold that government officials "made it happen on purpose."

Polls show that many Americans distrust the government on the subject of Sept. 11. A Zogby International poll taken in May found that 42% believed the government concealed evidence that contradicts official accounts. A Scripps Howard-Ohio University poll taken in August found that 36% believed it "very likely" or "somewhat likely" that federal officials allowed the attacks to occur because "they wanted the United States to go to war in the Middle East."

The theories — especially the notion that the towers fell in a controlled demolition — have become widespread enough to prompt official responses.

Last week, Brigham Young University announced that physics professor Steven E. Jones, co-chairman of the group Scholars for 9/11 Truth, would be put on indefinite leave while authorities investigated his claims that the buildings were intentionally demolished using explosives.

"Culturally, as a society, it becomes unhealthy," said Christopher Farrell of the conservative think tank Judicial Watch, which successfully filed suit against the government seeking the release of a video showing American Airlines Flight 77 hitting the Pentagon. The think tank was hoping to put to rest beliefs that the explosion was caused by a missile.

"If an individual demonstrated this sort of behavior, medical health professionals would recommend they treat it," said Farrell, a former military intelligence officer and the organization's director of investigations and research. "There's healthy skepticism, and then there's unhealthy."

This weekend's gathering in New York drew together strands of a scattered movement that has, until now, gained steam principally through the Internet.

There was radio host and activist Ralph Schoenman, who, during the course of a dizzying two-hour speech Friday, said that "not only was Mohamed Atta monitored by Mossad and the CIA, but he was being run by German intelligence," and that Hurricane Katrina "had been on the drawing board for years" as a way to "de-concentrate population" in inner cities.

There was Harvey Newman, a retired market researcher, who wrote a Caribbean-influenced "9/11 Truth" anthem ("Was the Pentagon building hit by an air-o-plane?/ And if it wasn't, please can you explain?")

There was Korey Rowe, 23, an Iraq war veteran from upstate New York who helped produce the documentary "Loose Change," which has been viewed online 10 million times. His baseball cap twisted backward, Rowe warned the audience about "agents provocateurs" who may have infiltrated the group in advance of anniversary events at ground zero. "We need to identify them now, and we need to remove them," he said.

A man in his 30s, conservatively dressed and soft-spoken, said he told almost no one about his attendance at 9/11 Truth meetings — not his co-workers at a corporate law firm and not his girlfriend. "It's considered part of the loony left," he said. "I'm very careful. I tell people who love me and will accept me for what I am."

For Williams, the former chef who lives in Duxbury, Mass., his fascination with the events of Sept. 11 grew so intense over the last two years that making pastries seemed pointless, then unbearable. He broke up with his girlfriend and now devotes six to eight hours a day to researching and writing, and hosts an Internet radio show and website. He has just sold the German and Turkish rights to two of his books, "The Puzzle of 9/11" and "9/11 101."