Couldn't those supposed Arabs seen on airport security videos checking onto flights just as easily have been Israelis? Couldn't it all have been a Jewish plot to trick the United States into a war against Israel's enemies?

In the months since, more and more evidence has been produced by investigators in the United States and around the world linking Osama bin Laden's al Qaeda network to the attacks that killed more than 3,000 people in New York, Washington and western Pennsylvania.

But it hasn't put an end to the conspiracy theories — they have just changed direction — and new ones keep popping up. And these are not the usual voices of doubt and dissent calling on the government to reconsider its foreign policy, or pick its allies more carefully, or even those who say the U.S. government bears a kind of moral responsibility for what happened on Sept. 11 because of the mistakes of the past.

There are voices popping up on Internet Web sites, in chatrooms and making the rounds in e-mail chains — even some conspiracy theorists who are packing hundreds of people into lecture halls — saying that evidence points to some direct level of involvement in the attacks by the U.S. government. And this at a time when an unprecedented numbers of Americans have rallied behind the government.

Where’s the Plane?

There is no smoking gun in any of the theories, but plenty of innuendo in schemes that run the gamut. Here is just a small sampling:

  Bush's decision to go ahead with an announced public appearance on the morning of Sept. 11, after he must have been informed that planes had been crashed into the World Trade Center, shows he knew of the attack plans before that morning and knew he would not be a target for the hijackers.

  Photographs of the Pentagon that morning and of the cleanup afterwards show that no plane crashed into the building because there was no debris from a jet and the damaged area of the building was too small — it had to have been a bomb planted inside to destroy the Office of Naval Intelligence, which would never have accepted the administration's story about who was behind the attacks in New York.

  Or maybe an unmanned fighter jet, radio controlled and flying at a low angle, crashed into the Pentagon. (In these scenarios it's never clear what happened to American Airlines Flight 77 and the 64 people on board.)

  The reason the tapes from the cockpit recorders of the four hijacked planes have not been released is because the voices they record are not human, but the voices of aliens.

  Even a congresswoman seems bitten by the bug, and wants an investigation into what President Bush knew and when he knew it — because so many of his friends have profited so handsomely from the resulting U.S. actions.

The National Character

Though at first glance it may seem strange that there should still be people looking for Sept. 11 villains besides bin Laden and his al Qaeda network, people who have studied conspiracy theories over the years say it is perfectly natural, and even a fundamental part of the American character.

"These are shattering experiences, when people's confidence and faith is shattered and their everyday routine is disrupted," Boston University sociology professor Daniel Monti said. "This is going to bring out the best we have to offer from some people, and from others it's going to bring out the worst."

Some scholars who study conspiracy theories say American ideals, such as the belief in free speech and an underlying distrust of power, make this country a natural breeding ground for alternate readings of momentous events such as the terror attacks of Sept. 11.

"Richard Hofstadter made this argument as long ago as the 1960s [in his book The Paranoid Style in American Politics]," said Michael Barkun, a political science professor at the Maxwell School of Syracuse University and the author of nine books on domestic terrorism and extreme right-wing groups. "There is a long conspiracist strain in American history from the Colonial period on."

"Part of the price we pay for living in a more open society is that human beings of all stripes and sizes feel they have not only the right but also the responsibility to speak up," Monti said. "Sometimes we hear a lot of gibberish and uninformed gossip and lies. That's part of the price we pay."

American Plots

Conspiracy theories are nothing new, of course. It is hard to think of a major incident in U.S. history that is not the subject of at least one alternate reading by people who refuse to accept the "official version."

And the possibility that the government could be involved in something that seems to run counter to national interests and the principles of democracy have been borne out by such incidents as the Watergate break-in and the Iran-Contra plot.

University of Maine at Machias professor Marcus LiBrizzi sees a thread of conspiracy theorizing running through American history, from even before the Salem witch trials. The Puritans came to the New World with a "world view that they were persecuted by agents of Satan" in the Catholic church, he said.

Among other early American conspiracy theories was the so-called New York Plot in 1741, in which fears of a slave uprising led to 34 people, both white and black, being executed, including 16 who were burned at the stake. The plot was later disproved.

In the 1820s anti-Masonic conspiracy theories gained strength in the United States when investigative journalist William Morgan disappeared when he was working on a story about the influence of Masons in American politics. Masons, who figured prominently among the Founding Fathers, have continued to be the villains in conspiracy theories to the present day.

The distrust of government that fuels much of the thinking was not alien to the framers of the Constitution themselves, LiBrizzi maintained. He said the concern the framers had about creating checks and balances and ensuring that power not be centered in one branch was indicative of a feeling that government was a necessary evil and had to be limited.

The government itself has even occasionally been snared by conspiracist thinking, such as during the McCarthy hearings of the 1950s, when communist agents were seen in every corner of American society.

Old News with a New Spin

These days, conspiracy mongers have a new and potent allies in the Internet and e-mail, which allow them to grab hold of and instantly spread any new nuggets that fits their construction.

Michael Ruppert, a former Los Angeles Police Department narcotics officer, has filled auditoriums in California, Texas, Oregon and Canada to explain what he sees as evidence that wealthy American interests were behind Sept. 11 — and he advertises those talks and the ideas on his Web site.

Then there's a best-selling book published in France that falls into the no-plane-hit-Pentagon school, and says the story was rigged to cover up a bombing targeting the new U.S. Naval Command Center that was carried out by people with classified access to the building.

The author, Thierry Meyssan, who had made a name for himself in France with exposés of the right-wing National Front, says in L'Effroyable imposture (The Horrible Fraud) that there was a secret CIA office in the World Trade Center that was carrying out illegal activities, and that the Bush administration was in negotiation with bin Laden on Sept. 11 itself, to work out an agreement to make him a scapegoat. The book has gotten little coverage in the United States, but it's worn a deep path in cyberspace.

Similarly, conspiracy theorists noticed quickly last week when U.S. Rep. Cynthia McKinney, D-Ga., said in an interview on a Berkeley, Calif., radio station that she wanted an investigation into what the Bush administration knew about the 9/11 attacks — before they occurred — suggesting that his friends are getting rich from the fallout.

Only hours after a story about her suggestion appeared in The Washington Post, the story was making the rounds in mass mailings on the Internet.

In one of the mailings, the link to the Post story appears with a headline that indicated the story went further than it does: "Mainstream News Article Stating Bush New [sic] Before 9/11." In the newspaper, the story bears the headline "Democrat Implies Sept. 11 Administration Plot."

McKinney's office did not return a call requesting an interview, but she issued a statement saying: "I am not aware of any evidence showing that President Bush or members of his administration have personally profited from the attacks of 9/11. A complete investigation might reveal that to be the case."

Whispers in Cyberspace

The way the story was spread shows how the Internet has given a new vitality to the theories, not only because of the ease it provides for disseminating ideas, but because of the very way the ideas can be presented.

"In a way the message becomes separated from the source on the Internet," said John Pavlik, a Columbia University journalism professor and executive director of the Conference for New Media. "You go online and you don't see the people making the Web site, all you see is the site, and if it's at all well done, it can seem credible."

"Everything on the Internet looks the same — the site for The New York Times and the site for some bizarre conspiracy theorist both look the same," Barkun said. "The differentiation that exists in print publications between the establishment and these fringe elements isn't there on the Internet. And the fact of multiple postings can make something seem more authoritative than if it were only up there once."

LiBrizzi, who has been teaching a class on conspiracy theories in American life for three years both in the classrom and through an online correspondence course, said that working on the Internet feeds the conspiracist's way of thinking.

"The architecture and the structure of it, with the ability to hyperlink and cut and paste kind of mirrors conspiracy thinking," he said. "The medium mirrors the mindset. Everything is interconnected."

Two Kinds of Thinking

Between the ceaseless churn of cyberspace, and the desire of conspiracy theorists to construct their elaborate scenarios, it can be extremely difficult to debunk their creations, and often presents dilemmas for government officials and journalists.

When left-leaning intellectuals such as Susan Sontag, Edward Said and Noam Chomsky were critical of U.S. policy in the weeks after Sept. 11, saying that it fueled understandable anger against America in developing countries, there were cries of outrage. Even measured criticism of administration policies and questions about the progress of the war on terror from Senate leader Tom Daschle, D-S.D., drew fire as being unpatriotic.

The conspiracy theorists have gone much further than any of those critics, but except for some snide editorials regarding the French taste for anti-Americanism and Meyssan's book, they have been largely ignored by mainstream media.

One journalist who appeared on a televised panel discussion with Meyssan, Jean-Bernard Cadier, the Washington bureau chief of the French news and talk radio network, Europe 1, crystallized the difficulty of facing some of these theorists head-on when he said, "I had the feeling that the more we tried to go into his arguments, the more we helped him, because we were not fighting with the same weapons he was."

Meyssan, for instance, discounts eyewitness accounts of the airliner hitting the Pentagon, and even says the government may have put beacons on the World Trade Center towers to ensure that the hijacked jet would hit them and planted explosives in the buildings so they would be sure to collapse.

"We tried to stick to some kind of truth and reality, and he obviously was not," Cadier said. Some of the arguments contained in conspiracy theories are often hard to dispute, giving them the kernel they need for resilience, but just as often there is some leap, a break in the chain of logic from a series of facts to the conclusion, such as Meyssan ignoring the disappearance of an entire plane with its passengers and crew.

Other times the thinking seems to work backwards, such as in arguments that if Bush himself or his associates profited from the attacks in some way — through increased defense spending or from the opening of Afghanistan for the construction of a pipeline — then he or someone in the administration must be to blame for the events of Sept. 11.

"You have to distinguish between functionalist thinking — looking at who benefits — as opposed to causal thinking — looking at what led to an event rather than at who gains from it," LiBrizzi said.

That kind of thinking has fueled questions about possible conspiracies from his own students. He said such issues as moves by the Justice Department to gain more power for investigators and prosecutors and to curtail individual rights, and the request by the Pentagon for the largest spending increase in two decades have caused some of his students to begin to question whether the administration could have had a hand in Sept. 11.