Here's a common reaction among Americans to this week's catastrophic plane attacks: "But I thought we were safe!"
Yes, by and large, the United States is a safe homeland. But one by one over the past 60 years, large-scale attacks on US soil - from Pearl Harbor to Oklahoma City to Columbine, and now the World Trade Center - have startled this nation into questioning its presumed invulnerability as an ark of tranquility on a global sea of troubles.
That historical sense of invincibility was greatly eroded Sept. 11, 2001. Suicidal fanatics carrying knives turned passenger jets into bombs. And now the nation will work hard to put its shell of safety back together again.
Where to begin? Airport security is a relatively easy place to start. In Boston, plans are already afoot to end curb-side check-in. Undoubtedly, metal-detection checkpoints will be strengthened. Airlines might soon have armed guards on board. Many other such measures could help prevent future airplane hi-jackings.
Public buildings will receive added security. Fire-fighting measures for skyscapers will be improved. Border checkpoints will become more strict.
But that's hardly enough. Security in the 21st century is more complex, more global, and more conceptual.
With US influence - from McDonald's to Alan Greenspan - now felt almost everywhere, resentments can build. If the US doesn't keep enough friends in the world, and fails to develop more clever intelligence gathering, it may experience more violent blowback from its actions.
Tuesday's attacks show a need for better homeland security. Right now, the federal government does that in piecemeal fashion. All the agencies dealing with border security need to be under common, seamless leadership. The FBI and CIA, whose counterterrorism efforts are commendable but imperfect, need to integrate their work.
But more than all that, Americans need to see security as coming from their strong ideals as a nation. Freedom, equality, and universal rights have spread around the world, making it safer. But even those are resented by terrorists and many others.
The founder of this paper, Mary Baker Eddy, wrote: "The broadcast powers of evil so conspicuous to-day show themselves in the materialism and sensualism of the age, struggling against the advancing spiritual era."
America's security now needs to change, but in a deeper sense, it's always advancing, despite opposition.