It's been more than five years since Sept. 11, and it's fair to ask why the United States has thus far been spared so much as a single further unpleasantness. Of course, an ugly explosion may go off any day in some American city, making such speculation look wildly premature. But even Osama bin Laden's notorious predilection for taking his time between these extravaganzas doesn't fully explain his delay in providing us with an encore.

There's certainly plenty of evidence that he wants to remain an actor on the world stage, and to make sure that we don't forget his presence there. Every few months, he or some spokesman of his shows up on Al Jazeera in a new video tape, giving orders to his allies and followers and issuing bloodthirsty threats about what is going to happen to his foes, especially the Great Satan. One could be forgiven for speculating that he is auditioning for his own talk show on CNN. But where's that next bomb?

To be sure, he and/or other Muslim fanatics have hardly been idle in the years since Sept. 11. Suicide bombers and garden-variety terrorists have been busy blowing themselves and innocent Westerners up in London, Madrid, Bali and half a dozen other vulnerable cities around the world. But New York, Washington and other American cities are conspicuously not on the list. Why?

The likeliest explanation is that American counter-measures have been working, and it is no longer so easy to slip suicide bombers into the United States and pull off devastating attacks. The Democrats in Congress may be furious at George W. Bush for eavesdropping on phone conversations between Americans and suspicious foreigners abroad, and monitoring the financial doings of various dubious operators, but they are almost certainly not more exasperated than Bin Laden. International terrorism is no longer a game played entirely in the dark.

But there is at least one other possible explanation. Muslim fanatics had been conducting successful attacks on American targets abroad for nearly 30 years before Sept. 11. They had bombed our embassies in Kenya and Tanganyika, all but sunk the destroyer Cole in Aden, and simply assassinated various American officials around the world -- all without attracting much notice from the American public, and without suffering any serious retaliation. But the attacks on Sept. 11, in New York and Washington, shook the American people fully awake, and within months Bin Laden's protectors in Afghanistan had been ousted and bin Laden himself was on the run.

Is it too much to suspect that bin Laden concluded that bombing America itself had been a strategic mistake, and that when he noticed that the American public was dozing off to sleep again he decided not to give it another poke in the eye?

Whatever the explanation, it almost certainly doesn't mean that bin Laden and his fellow Muslim terrorists have forgotten about us, or decided that we are too dangerous to attack on our own soil. At best, they have simply decided to pick off easier targets first -- including American targets abroad. In due course, when they have infiltrated or recruited a sufficient number of agents here, and above all when they have acquired a few nuclear weapons from friendly nations, they will stage an attack on the American homeland that will make Sept. 11 look like a garden party.

That, to be sure, will have the disagreeable side effect of awaking the American public (or what's left of it) again. We may even reinstitute some of the "unconstitutional" surveillance procedures that the ACLU is today so busy urging the courts to abolish. Or we may simply be remembered historically as the freest nation ever destroyed by indifference to its own danger.

But, one way or another, at a time of their choice, we will hear from the Muslim fanatics again.