It was Geoffrey Hoon who converted and convinced me. Six weeks ago, in this column, I described myself as an unlikely hawk. And until last Thursday evening, a hawk of sorts I remained. For I accepted the doctrine of the pre-emptive strike - the right of a nation under threat to take early action against a potential aggressor. I still do. But when I heard the secretary of state for defence - appearing on a special edition of Question Time - give the official explanation of why military action against Baghdad might be a regrettable necessity, I became a Gulf war dove. Hoon's indictment of the Baghdad regime was impressive and irrefutable. But most of it had absolutely nothing to do with Saddam Hussein's threat to the west. One item on the charge sheet was a comparison between infant mortality rates in the parts of Iraq under Saddam's personal control and those outside his area of direct influence. As Hoon explained that the further a family lived from the centre of power, the greater its children's life expectancy, I realised what should have been obvious for weeks. We are being encouraged to support the war not because Saddam is a threat, but because he is evil.  Evil he undoubtedly is. But that is not in itself sufficient justification for starting a war that will kill thousands (perhaps tens of thousands) of innocent civilians. If it were, God knows how many countries we would be preparing to invade. So next Tuesday, when at last we see the dossier that explains the need for a "regime change", we must not be satisfied with a catalogue of wickedness.  Indeed, the more that the president and the prime minister base their argument on the undoubted villainy of Saddam, the more we are entitled to believe that they cannot demonstrate, even to their own satisfaction, that he is likely to attack Israel or the west.  For next week's dossier to be intellectually convincing its claims must be judged against three criteria. Does Saddam possess, or is he likely to acquire, weapons of mass destruction? Does he possess or is he likely to acquire delivery systems, which will allow him to target America and her allies? And assuming he possesses both warheads and missiles, are there any circumstances in which it can be plausibly agreed that he would use them?  No one seriously doubts that Saddam already possesses chemical and biological weapons and that, sooner or later, he will add a primitive nuclear capability to his arsenal. And he is building, perhaps has built, some sort of rocket, as well as a crude version of the flying bomb that was used on London during the last years of the second world war. But the third question still has to be asked. Why should Saddam launch a doomed attack on the most powerful military complex that the world has ever known? I agree he is bad enough to do it. But is he sufficiently insane to set in train a course of action that can only end in his own total destruction?  The official answer to that question is that he happily gassed his own people when they defied his will, so why should we doubt his willingness to gas Americans and Israelis? On such a glorious non sequitur is the case for war constructed. Saddam knew he could get away with mass murder inside his own boundaries. Indeed, the genocide of the marsh Arabs probably made his tyranny more secure. It only needs one gas-filled warhead to land on Long Island for him and his regime to be wiped out. It does not even have to explode.  That fate cannot be avoided - as some of the more fatalistic scenarios suggest - by contracting out the dirty work. It is possible   for freelance fanatics to send envelopes of anthrax through the post and suicide bombers do not need much logistical support. But intercontinental ballistic missiles with nuclear warheads can only be landed from sophisticated installations by trained technicians. If Saddam was behind it, the world would know and he would pay the price. No doubt he does give comfort and support to al-Qaida terrorists. But if America intends to invade every country that does the same, we are on the eve of another year's war.  To believe that Saddam is likely to attack the west - the only justification for war - is to believe he is a suicidal lunatic. That is an allegation that I have not heard even George Bush make against him. Indeed, the president is now barely even bothering to pretend that it is the fear of attack that prompts American action. Only two of the five requirements that he told the United Nations Saddam must meet had anything to do with the security of the United States. The other three concerned moral conduct not military capability.  For next week's dossier to make me a hawk again it will have to explain why Saddam is bent on self-destruction. Up to now nobody has even tried.