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But my favorite e-mail message offered some tongue-in-cheek security advice.

Mads Oyen, a policy specialist at Unicef in New York, suggested removing from a plane any specific seat that had been used by a would-be terrorist. “If he used, say, 36E, remove that seat. Then this cannot be tried again,” Mr. Oyen wrote.

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After Sept. 11, we Americans indulged our faith in the god of technocracy. We expanded the country’s information-gathering capacities so that the National Security Agency alone now gathers four times more data each day than is contained in the Library of Congress.

We set up protocols to convert that information into a form that can be processed by computers and bureaucracies. We linked agencies and created new offices. We set up a centralized focal point, the National Counterterrorism Center.

All this money and technology seems to have reduced the risk of future attack. But, of course, the system is bound to fail sometimes. Reality is unpredictable, and no amount of computer technology is going to change that. Bureaucracies are always blind because they convert the rich flow of personalities and events into crude notations that can be filed and collated. Human institutions are always going to miss crucial clues because the information in the universe is infinite and events do not conform to algorithmic regularity.

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Meanwhile, the Transportation Security Administration has to be seen doing something, so it added another layer to its stage play, “Security Theater” — more baggage regulations, more in-flight restrictions.

At some point, it’s worth pointing out that it wasn’t the centralized system that stopped terrorism in this instance. As with the shoe bomber, as with the plane that went down in Shanksville, Pa., it was decentralized citizen action. The plot was foiled by nonexpert civilians who had the advantage of the concrete information right in front of them — and the spirit to take the initiative.

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For better or worse, over the past 50 years we have concentrated authority in centralized agencies and reduced the role of decentralized citizen action. We’ve done this in many spheres of life. Maybe that’s wise, maybe it’s not. But we shouldn’t imagine that these centralized institutions are going to work perfectly or even well most of the time. It would be nice if we reacted to their inevitable failures not with rabid denunciation and cynicism, but with a little resiliency, an awareness that human systems fail and bad things will happen and we don’t have to lose our heads every time they do.

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