I'm going to propose a worst case scenario for the next fifty years, mostly because it's time to think about exactly how much we want to sacrifice while fighting terrorism and nuclear proliferation.

It seems that not only are nuclear weapons spreading, but the rate is increasing as well. When Pakistan and India's nuclear tests are still in the recent past, it suddenly becomes a certainty that North Korea has nuclear bombs as well. Perhaps our efforts to resolve the North Korea crisis without a second Korean war will meet with great success. If George Bush manages to get the North Koreans to destroy rather than merely freeze their nuclear program, he will have an accomplishment to be proud of - and have stood firm in his refusal to offer more concessions in return for a 'horse already bought'. Of course the North Koreans will want some proof that our aid cannot be revoked before they take such a drastic step, and they will probably want more than they charged for the freeze, but hope springs eternal.

Meanwhile let's suppose that more countries continue to acquire the weapons, while scientists in countries which already have the technology occasionally need extra income after they retire, get fired, get laid off, or encounter unexpected expenses. Sooner or later terrorists will obtain nuclear bombs.

A missile shield won't prevent terrorists from loading a bomb into the back of an SUV and driving it into New York city. It would probably be hard to sneak that much radioactive material into the country, but I'm not sure what barriers we have after that. The sort of country where vehicles were searched while being driven into big cities might well be more repressive than cold war Russia - but if it would really work and it's the only way it would be worth it. Otherwise no large city is safe from a organization which couldn't stop even if it wanted to - assuming there's no central control as many suspect. If you have a bunch of independent sub groups who decide what to do for themselves, one or another will always want to test their new idea once the murderous momentum has gotten going.

I don't discuss this nightmare because I want to try to scare people. It could well be this is just another crisis, and it will be resolved in the next few years with non draconian measures. If not, what would we be willing to give up? Free speech? Freedom or religion? Freedom from collective punishment via 'bills of Attainder'? All these are freedoms the terrorists don't observe - and all are freedoms they make use of to spread their poison. They are also freedoms that cannot be touched without serious danger to a free society, and severely curbing them is almost like implicitly admitting the idea of a free society has failed.