Just a ruse to justify settling old scores with Iraq, which has long defied United Nations efforts to strip it of its illicit weapons of mass destruction? Or a ploy to help justify Mr Bush's decision to scrap the Anti-Ballistic Missile Treaty with Russia and build new missile defences? To many a seasoned anti-proliferation warrior, the president was simply stating the obvious: in a world of terrorism without constraint, tackling the proliferation of nuclear, chemical and biological weapons is just as urgent as ripping up the terrorist networks that might seek to make use of them.

As in any war, it helps to know the enemy. There are more than three of them. In a report published just before the Bush administration came into office, America's then secretary of defence, William Cohen, picked out "at least 25" countries that either possess, or are trying to develop, weapons of mass destruction or the means to deliver them. Since chemical and biological weapons are outlawed, and the Nuclear Non-Proliferation Treaty (NPT) allows for only five official nuclear powers--the United States, Russia, China, Britain and France--plenty of governments are clearly up to no good.

The government's plan is to establish a computer network linking every reservation system in the United States to private and government databases. The network would use data-mining and predictive software to profile passenger activity and intuit obscure clues about potential threats, even before the scheduled day of flight.

It might find, for instance, that one man used a debit card to buy tickets for four other men who sit in separate parts of the same plane -- four men who have shared addresses in the past. Or it might discern an array of unusual links and travel habits among passengers on different flights.