ventually, in those frantic first months after September 11, I would hear the allegation in a mosque near the Afghan border and a living room scarcely a mile from the Pakistani president's house. I'd see interviews that followed the story to Egypt, and Indonesia, and France. But the first time I heard it was at a Fairfax, Va., strip mall, from a friendly Palestinian-American kid working at his family's copy shop. "Have you," he asked, "heard about the 4,000 Jews?"

The 4,000 Jews. Never 3,000. Never 5,000. That figure lies at the heart of a conspiracy theory that managed to zip around the globe before Lower Manhattan even stopped smoldering: Eerily specific, it refers to the number of Jewish World Trade Center workers alleged to have called in sick on September 11–presumably, the theory holds, because they'd been tipped off by Israel or the media or whoever the true masterminds had been. At once slanderous and outlandish, the story traveled nonetheless, parroted by shopkeepers and cabbies, street agitators and religious zealots. Alternative theories fingered an out-of-control CIA, an oil-hungry U.S. government, and even a defeated presidential candidate: "Al Gore, a die-hard Jew, might have taken revenge," railed a mullah at a Pakistani rally last October.

Are the conspiracy theories merely the Islamic fringe's version of Americans' Area 51 UFO speculation, the toxic offspring of a marriage between suspicious worldviews and Internet access? Actually, no. Polling numbers show that suspicion of the American version of events runs deep and wide. Eighty-six percent of Pakistanis, 74 percent of Indonesians, and 43 percent of Turks told Gallup last winter that they don't believe Arabs were responsible. Educated and illiterate alike embrace the story. "[The] Mossad might have hired Muslim youths masquerading itself as an Islamic organization," speculates Kafeel Ahmed, a Karachi computer operator. Even in Kuwait, liberated by Americans barely a decade ago, a full 89 percent told pollsters that they didn't believe Uncle Sam.

It's not just Muslims. In France, The Horrifying Fraud, a book alleging American right-wingers launched the attacks via guided missile and computer-controlled planes, sold 210,000 copies and rocketed up the bestseller list. Newspapers panned the book, but that doesn't matter to some. "When I watched the attacks on TV last September I said, 'Something isn't right. This was all set up by Americans,' " says Sylvie Jumel, 43, a government worker in Paris. "The hypothesis interested me right away." Foreign rights have sold in 16 countries, from China to Bulgaria. "[Readers] feel that something is being hidden," the author, Thierry Meyssan, told U.S. News. "The book has given them back their freedom to think."

From Holocaust denial to Elvis-is-alive lore, conspiracy theories have a storied history. Experts offer various explanations for this one, from political marginalization to a logical desire not to see one's co-religionists as mass murderers. Push people who say the attacks were a fraud and you'll find everything from abiding anti-Americanism to paranoia about vast anti-Muslim schemes to a perverse kind of self-loathing–as with Shariq Ali, a Karachi bank employee who thinks his fellow Muslims lack the technical savvy to carry out a complex plot. "If Muslims have such technology and expertise," he asks, "then why are they being singled out and killed in Palestine, Iraq, Afghanistan, Kashmir, and other places?"

But in a sense, the question of belief–Why don't others see things our way?–is the real theme of global politics post-9/11. Faced with an enemy willing to take the grand unknowables– life, salvation, martyrdom–on faith, the United States is having trouble getting parts of the world to take its word on something that happened live on TV. Changing that imbalance is crucial if Washington wants to build a new world without terrorism. "If this is a war, and the U.S. has declared it a war, winning hearts and minds is very important," says Hussain Haqqani, a former adviser to two Pakistani prime ministers. "Believing the account of how it started is the basic first step."

With Aamir Latif in Karachi and Benjamin Sutherland in Paris