People often wind up believing their own cover story.Former British prime minister Tony Blair, for example, is trapped forever in the rationalisations he used in 2003 to explain why he was going along with George Bush's invasion of Iraq. He has been at it again, telling the BBC that "radical Islam" is the greatest threat facing the world today. But is militant Islam really a bigger threat to the world than the possibility of a major nuclear war - happily now in abeyance, but never really gone? Bigger than the risk that infectious diseases are going to make a major comeback as antibiotics become ineffective? Bigger even than the threat of global warming? It depends on what you mean by "radical Islam," of course. In some Western circles, any Muslim who challenges Western policies is by definition an Islamist radical. But if it means Sunni Muslims who believe in the Salafist interpretation of Islam and are personally willing to use terrorist violence to spread it, then there aren't very many of them: a few hundred thousand at most. These people are unlikely to start blowing things up in New Jersey or Bavaria, though they are a serious threat to fellow Muslims living in their own countries. It's a big, ugly problem for countries like Iraq and Pakistan, but it is a pretty small problem for everybody else. The number of people killed by "radical Islamic" terrorists in the past decade outside the Muslim world is probably no more than 15,000. None of these deaths is justifiable, but it is weird to insist that a phenomenon that causes an average of, say, 1500 non-Muslim deaths a year is the greatest threat. Yet the people who launched the "war on terror" do say that, as do many others who built their careers by pushing the same proposition. They do it by the simple device of warning (to quote Blair) that "there is the most enormous threat from the combination of this radical extreme movement and the fact that, if they could, they would use nuclear, chemical or biological weapons. You can't take a risk with that happening." Never mind the quite limited damage that terrorists actually do. During the Cold War, the United States and the Soviet Union had 10,000 nuclear weapons ready to launch at each other. If they had ever gone to war, hundreds of millions of people would have been killed - even several billion, if it had caused a nuclear winter.And of course the two countries had huge biological and chemical warfare capabilities too. If "radical Islamists" ever got their hands on a nuclear weapon, it would be one bomb, not 10,000 warheads. If they managed to explode it, there would be a local disaster, not a global holocaust.The worst poison gas attack ever, on the Tokyo underground system in 1995, killed only 13 people, and although germ warfare could be hugely destructive of human life, it requires scientific capabilities that are very difficult to master. Besides, just how does invading various Muslim countries shrink any of these dangers? It probably increases them, actually, by outraging many Muslims and providing the extremists with a steady flow of recruits. Terrorism, by radical Islamists or anybody else, is a real threat but a modest one. It cannot be "defeated", but it can be contained by good police work and wise policy choices.It might make it into the top 10 global threats, but certainly wouldn't make it into the top three.Anybody who says it does has something to sell or something to hide.