The London bombing once again begs the question: Why haven't terrorists struck the United States in the last four years?
Certainly the effects of the Sept. 11, 2001, attacks are still felt by Americans. Unfortunately, terrorists have succeeded in changing how we live our daily lives.
Americans worry more about being blown up now than when thousands of Soviet ICBMs with multiple nuclear warheads were pointed at the United States.
These days, we live under the constant fear of being the next victim of a random act, a mentality that makes us more fearful and less generous to strangers and forces changes in behavior that cost us all time and money.
Nonetheless, it is useful to ponder why the bad guys haven't struck within the United States itself since 9-11. It certainly is not because Osama & Co. hate us less than they once did. If anything, the U.S. destruction of his puppet regime in Afghanistan, its invasion of Iraq and the American-led war on terror make us even less popular among Islamic extremists.
And it is not as though they have given up their efforts to wreak mayhem and havoc.
The bombings in London's public transit system were similar to the attack on the Madrid rail system that took almost 200 lives in March 2004. In addition, there have been sporadic acts of terror elsewhere around the globe since 9-11.
Of course, the fear is that al-Qaida is just biding its time planning some really horrific act, perhaps employing a weapon of mass destruction, against the United States. Sadly, that could well be the case.
Yet, we might also consider the possibility that the U.S. government's response to 9-11 has been working. What if we have thwarted active terrorist plots or discouraged al-Qaida's planners from focusing here, forcing them to concentrate their efforts overseas?
After all, it would seem that the New York, Boston, Chicago or Washington subways, San Francisco's Golden Gate Bridge or Los Angeles' freeways or shopping malls would be just as inviting for the low-tech kind of terrorism that occurred in London and Madrid.
If that is the case, then perhaps the Bush administration's efforts - which have raised the hackles of civil libertarians who argue the stepped-up security endangers individual rights - are working.
Its tough stance on controlling foreign visitors to the United States might be worth the perceived insult felt by those overseas, and the loss of revenue for some U.S. businesses.
Maybe the Patriot Act, which gave the Justice Department new tools to deal with the flow of money to terrorists and provided investigative powers that drive the American Civil Liberties Union nuts, is worth it.
Most Americans would gladly accept officials looking at their library cards or giving the FBI broader powers to snoop into peoples' lives if it helped prevent terrorism.
Is it possible that the lockup of captured al-Qaida fighters at Guantanamo Bay might be yielding the type of intelligence that has allowed U.S. security personnel to short-circuit extremist plots?
If so, then maybe the critics, foreign and domestic, of the prison there, and of U.S. cooperation with other nations' security forces that don't have the same constitutional constraints on treating detainees as do Americans, might want to reconsider their view.
Or maybe opposing the U.S. military presence in Afghanistan and Iraq has used up al-Qaida's men and money, forcing it to concentrate its battle against America there, since those parts of the world are closer to al-Qaida's home.
And there is always the possibility that al-Qaida has decided that attacking the United States might not be worth the political costs. After all, it would once again create a post 9-11 sense of national unity behind a strong military response. And no doubt that would give Bush a mandate to do whatever he thinks necessary to combat terrorism.
Obviously, it is impossible to know for certain why something does not occur. Clearly, however, the lack of a terrorist incident in the United States since 9-11 is not a random act of kindness. It stems from U.S. government measures, or terrorists' decision that their self-interest requires them to look elsewhere for targets of opportunity.
Let's keep this in mind as, hopefully, the United States remains terrorism-free.
Perhaps our defenses against terrorism are working, which would argue for more of the same.