The almost-unbelievably amateurish nature of the recent Times Square "device" — so poorly designed and built it’s hard to call it a "bomb" — has prompted a new round of speculation as why well-organized, successful terrorist attacks aren’t more common.

Into the fray steps Bruce Schneier, the Internet’s favorite security commentator (and a distinguished cryptographer, too), who says:

As the details of the Times Square car bomb attempt emerge in the wake of Faisal Shahzad’s arrest Monday night, one thing has already been made clear: Terrorism is fairly easy. All you need is a gun or a bomb, and a crowded target. Guns are easy to buy. Bombs are easy to make. Crowded targets — not only in New York, but all over the country — are easy to come by. If you’re willing to die in the aftermath of your attack, you could launch a pretty effective terrorist attack with a few days of planning, maybe less.

But if it’s so easy, why aren’t there more terrorist attacks like the failed car bomb in New York’s Times Square? Or the terrorist shootings in Mumbai? Or the Moscow subway bombings? After the enormous horror and tragedy of 9/11, why have the past eight years been so safe in the U.S.?

There are actually several answers to this question. One, terrorist attacks are harder to pull off than popular imagination — and the movies — lead everyone to believe. Two, there are far fewer terrorists than the political rhetoric of the past eight years leads everyone to believe. And three, random minor terrorist attacks don’t serve Islamic terrorists’ interests right now.

His explanation is compelling. We don’t have more well-organized, successful terrorist attacks at the moment because, at the moment, the well-organized, successful groups don’t have much interest in launching terrorist attacks.

That’s not to say the problem’s solved. Just that the particular harm we’re most afraid of isn’t as high on our enemies’ agenda as it is on our’s.

Schneier’s reasoning reminds me of one of the more popular variants of Occam’s Razor:

The simplest explanation is usually the best.

Einstein’s version was: "Make everything as simple as possible, but not simpler."

Works just as well.