Dr Rowan Williams, the man strongly tipped to become the next Archbishop of Canterbury, has said that any American offensive against Iraq would be "immoral". It would not be part of a just war, because innocent people would be killed.

But the Christian doctrine of a just war does not say that the innocent must not be killed, only that a state waging a just war should not intend to kill the innocent. There is a world of difference.

Deliberately killing the innocent is what our enemies, the terrorist suicide bombers, do. The West's response has been proportionate and carefully targeted. Of course, in modern warfare, innocent people do get killed accidentally, or "co-laterally" as the awful jargon has it; but we and our allies have not deliberately set out to kill the innocent.

I would argue against Dr Williams that, on the contrary, it would be immoral not to wage war on Saddam Hussein with the intention of ousting him and his brutal regime. This is because it is always wrong not to try to do what is right.

Saddam has terrorised and persecuted the Kurdish people in northern Iraq for decades. He runs a regime of terror, inflicting torture and death on his political opponents.

Saddam supports the suicide bomb attacks on Israel and sends money to the families of these bombers - money that would be better spent on his own nation's children. He continues to defy lawful authority by refusing to comply with the United Nations' demand that he allows inspection of his alleged production centres of nuclear and biological weapons. It is he who is blatantly immoral, not the Western powers seeking to defeat him.

Dr Williams seems to me to be a man of very confused moral sense. He does not support the war on terrorism. He says he wants to "understand" the terrorists' motivation. According to Dr Williams' confused moral sense, the terrorists who attacked the twin towers had no choice: "We have something of the freedom to consider whether or not we turn to violence and so, in virtue of that very fact, are rather different from those who experience their world as leaving no other option."

Dr Williams is being lauded all over the newspapers as a man who excites us to awe and affection, a real man of God. He is even described here and there as a saint. In fact, as his writings reveal, he is an old fashioned class warrior, a "progressive" thinker, a typical bien pensant despiser of Western capitalism and the way of life that goes with it.

Perhaps this would not matter much in ordinary times, but in the thick of a war against terrorism, when the future of western civilisation is under threat, such posturing is suicidal. What havoc Dr Williams might wreak. Please do at least one thing right, Mr Blair: don't appoint this man to the highest office in the Church of England.

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