For the past five years, Americans have been regularly regaled with dire predictions of another major al Qaeda attack in the United States. In 2003, a group of 200 senior government officials and business executives, many of them specialists in security and terrorism, pronounced it likely that a terrorist strike more devastating than 9/11 -- possibly involving weapons of mass destruction -- would occur before the end of 2004. In May 2004, Attorney General John Ashcroft warned that al Qaeda could "hit hard" in the next few months and said that 90 percent of the arrangements for an attack on U.S. soil were complete. That fall, Newsweek reported that it was "practically an article of faith among counterterrorism officials" that al Qaeda would strike in the run-up to the November 2004 election. When that "October surprise" failed to materialize, the focus shifted: a taped encyclical from Osama bin Laden, it was said, demonstrated that he was too weak to attack before the election but was marshalling his resources to do so months after it.

On the first page of its founding manifesto, the massively funded Department of Homeland Security intones, "Today's terrorists can strike at any place, at any time, and with virtually any weapon."

But if it is so easy to pull off an attack and if terrorists are so demonically competent, why have they not done it? Why have they not been sniping at people in shopping centers, collapsing tunnels, poisoning the food supply, cutting electrical lines, derailing trains, blowing up oil pipelines, causing massive traffic jams, or exploiting the countless other vulnerabilities that, according to security experts, could so easily be exploited?

One reasonable explanation is that almost no terrorists exist in the United States and few have the means or the inclination to strike from abroad. But this explanation is rarely offered.

HUFFING AND PUFFING

Instead, Americans are told -- often by the same people who had once predicted imminent attacks -- that the absence of international terrorist strikes in the United States