Bruce Schneier: By today's rules, I can carry on liquids in quantities of three ounces or less, unless they're in larger bottles. But I can carry on multiple three-ounce bottles. Or a single larger bottle with a non-prescription medicine label, like contact lens fluid. It all has to fit inside a one-quart plastic bag, except for that large bottle of contact lens fluid. And if you confiscate my liquids, you're going to toss them into a large pile right next to the screening station -- which you would never do if anyone thought they were actually dangerous.

Can you please convince me there's not an Office for Annoying Air Travelers making this sort of stuff up?

I often read blog posts about how someone could just take all their three-ounce bottles -- or take bottles from others on the plane -- and combine them into a larger container to make a bomb. I can't get into the specifics, but our explosives research shows this is not a viable option.

If a TSO finds you or the contents of your bag suspicious, you might get interviewed and/or have your bags more closely examined. If the TSO throws your liquids in the trash, they don't find you a threat.

BS: When can we keep our shoes on?

KH: Any time after you clear security. Sorry, Bruce, I don't like it either, but this is not just something leftover from 2002. It is a real, current concern. We're looking at shoe scanners and ways of using millimeter wave and/or backscatter to get there, but until the technology catches up to the risk, the shoes have to go in the bin.

BS: This feels so much like "cover your xxx" security: you're screening our shoes because everyone knows Richard Reid hid explosives in them, and you'll be raked over the coals if that particular plot ever happens again. But there are literally thousands of possible plots.

So when does it end? The terrorists invented a particular tactic, and you're defending against it. But you're playing a game you can't win. You ban guns and bombs, so the terrorists use box cutters. You ban small blades and knitting needles, and they hide explosives in their shoes. You screen shoes, so they invent a liquid explosive. You restrict liquids, and they're going to do something else. The terrorists are going to look at what you're confiscating, and they're going to design a plot to bypass your security.

That's the real lesson of the liquid bombers. Assuming you're right and the explosive was real, it was an explosive that none of the security measures at the time would have detected. So why play this slow game of whittling down what people can bring onto airplanes? When do you say: "Enough. It's not about the details of the tactic; it's about the broad threat"?

Just as there hasn't been a second 9/11 in the six years that have passed, there wasn't an attack in the six years prior. Would Kip claim that between 1995 and 2001 we were just lucky? Or there was no threat? Or the existing security, apart from cockpit doors, was sufficient?

While Kip Hawley has, by now, revealed himself as a true believer, more or less immune to rational argument, I still have a modicum of faith in the traveling public. The last time I traveled by air (and I no longer travel by air to any destination that I can reach in a day's drive, because even the shortest trip by air now requires about 8 hours) I printed out about two dozen copies of the New York Times article on "Security Theater at the TSA." While waiting around the airport I left copies in areas where people would be likely to pick them up. I left copies on the aircraft in the pouch of the seat in front of me. I left copies on tables in the baggage claim area. In several cases I observed people picking one up and reading the article.

I propose we all engage in this behavior. Every time you travel by air, find the most damning report on the TSA you can find from a credible source. Print two dozen copies, and as you travel sow the copies wherever the traveling public gathers and would be likely to pick one up and read it. Leave them tucked inside in-flight magazines. I don't believe it will be a quick fix, but over time the TSA will fall into such disrepute that Congress will be goaded into taking action.