DR Rowan Williams, the man who is to be the next Archbishop of Canterbury, has said that we should not make war on Iraq.

This is the same Dr Williams who said that he opposed military retaliation after the September 11 attacks. He says we ought instead to talk to the perpetrators or their representatives and address the root causes which encourage terrorist activity to thrive.

Generally, of course, any reasonable person would be in favour of talks and negotiations; but the likes of Osama bin Laden and Saddam Hussein have proved time and time again that they have no use for negotiations. This is because, unlike a conventional enemy, they have no rational demands. They do not seek agreement. They seek our destruction. Therefore, I believe Dr Williams is mistaken and we have no alternative but to wage war on the terrorists.

There is no doubt at all about the deadly motives of Osama and his al Qaida network: they attacked American embassies in Africa, an American warship at anchor and then New York and Washington where, let us not forget, more than 3,000 people were murdered. All the intelligence available to the West indicates that al Qaida is regrouping and preparing for further attacks on our cities. There is no doubt also that they are trying to get hold of - perhaps have hold of already - weapons of mass destruction and they will not hesitate to use them.

The same goes for Saddam Hussein. He has used biological and chemical weapons on his own people; and I'm afraid we in the western alliance must take part responsibility for this. At the end of the Gulf War of eleven years ago, the Americans and ourselves said to the Iraqi people that if they arose against Saddam we would support them. We did nothing. They did rise up and were savagely put down by Saddam. We must not make the same mistake again.

What is the case against Saddam? Simply that he has proved himself to be a mass murderer. He is in defiance of many UN resolutions. He hides his weapons of mass destruction and moves them around the country, often concealing them on hundreds of remote farms.

Iain Duncan Smith was right to point out last weekend that the next generation of Saddam's ballistic missiles will be able to reach London. The Iraqi dictator has also threatened to destroy Israel - the only mature democracy in the Middle East, practising political pluralism and religious toleration.

There is everything to be said for diplomatic negotiations when even the most ferocious enemy has a case to make and a rational point of view. Men like bin Laden and Saddam Hussein do not practise rational politics and it is wrong to appease them: any demands they made would be ratcheted up again and again. It is our Christian duty to refuse to appease evil men and their evil organisations and regimes and to destroy them before they destroy us.

Peter Mullen is Rector of St Michael's, Cornhill, in the City of London, and Chaplain to the Stock Exchange.