That is not all that was carefully prepared ahead of yesterday's launch of the attacks. Crucially for a modern war, public opinion formers at home have been prepared and marshalled into line with a striking degree of unanimity. The voices of dissent can barely be heard over the chorus of approval and self-rightous enthusiasm.

It's the latter that is so jarring, and it's a sign of how quickly the logic of war distorts and manipulates our understanding. War propaganda requires moral clarity - what else can justify the suffering and brutality? - so the conflict is now being cast as a battle between good and evil. Both Bin Laden and the Taliban are being demonised into absurd Bond-style villains, while halos are hung over our heads by throwing the moral net wide: we are not just fighting to protect ourselves out of narrow self-interest, but for a new moral order in which the Afghans will be the first beneficiaries.

The extent to which this is all being uncritically accepted is astonishing. Few gave a damn about the suffering of women under the Taliban on September 10 - now we are supposedly fighting a war for them. Even fewer knew (let alone cared) that Afghanistan was suffering from famine. Now the west is promising to solve the humanitarian crisis that it has hugely excerbated in the last three weeks with its threat of military action. What is incredible is not just the belief that you can end terrorism by taking on the Taliban, but that doing so can be elevated into a grand moral purpose - rather than it incubating a host of evils from Chechnya to Pakistan.

Is this gullibility? Naivety? Wishful thinking? There may be elements of these, but what is also lurking here is the outline of a form of western fundamentalism. It believes in historical progress and regards the west as its most advanced manifestation. And it insists that the only way for other countries to match its achievement is to adopt its political, economic and cultural values. It is tolerant towards other cultures only to the extent that they reflect its own values - so it is frequently fiercely intolerant of religious belief and has no qualms about expressing its contempt and prejudice. At its worst, western fundamentalism echoes the characteristics it finds so repulsive in its enemy, Bin Laden: first, a sense of unquestioned superiority; second, an assertion of the universal applicability of its values; and third, a lack of will to understand what is profoundly different from itself.

This is the shadow side of liberalism, and it has periodically wreaked havoc around the globe for over 150 years. It is detectable in the writings of great liberal thinkers such as John Stuart Mill, and emerged in the complacent self-confidence of mid-Victorian Britain. But its roots go back further to its inheritance of Christianity's claim to be the one true faith. The US founding recipe of puritanism and enlightenment bequeathed a profound sense of being morally good. This superiority, once allied to economic and technological power, underpinned the worst excesses of colonialism, as it now underpins the activities of multinational corporations and the IMF's structural adjustment programmes.

But recognising this need not be the prelude to an onslaught on liberalism - just the crucial imperative of recognising that, like all systems of human thought, liberalism has weaknesses as well as strengths. We need to remember this: in the heat of battle and panicky fear of terrorism, liberal strengths such as tolerance, humility and a capacity for self-criticism are often the first victims.

In all systems of human thought, there are contradictions that advocates prefer to gloss over. One of the most acute in liberalism is between its claim to tolerance and its hubristic claim to universality, which Berlusconi's comments on the superiority of western civilisation brought embarrassingly to the fore two weeks ago. It was the sort of thing many privately think, but are too polite to say, argues John Lloyd in this week's New Statesman. He owns up with refreshing honesty that in the conflict between Islam and Christianity: "Their values, or many of them, contradict ours. We think ours are better."

Once this kind of hubris is out in the open, at least one can more easily argue with it. These aren't just academic arguments for the home front before the cameras start rolling on the exodus of refugees into Pakistan. September 11 and its aftermath launched both an aggressive reassertion and a thoughtful re-examination of our culture and its values. Both will have a lasting impact on our relations with the non-western world, not just Muslim world. It is that aggressive reassertion that smacks of fundamentalism, a point obliquely made by Harold Evans recently: "What do we set against the medieval hatreds of the fundamentalists? We have our fundamentals too: the values of western civilisation. When they are menaced, we need a ringing affirmation of what they mean." The only problem is that "ringing" can block out all other sound and produce nothing but tinnitus.

There is a compelling alternative for how we can coexist on an increasingly crowded planet. Political philosopher Bhikhu Parekh starts from the premise that "the grandeur and depth of human life is too great to be captured in one culture". That each culture nurtures and develops some dimension of being human, but in that process it misses out others, and that progress will always come from dialogue between cultures. "We are all prisoners of our subjectivity," argues Parekh, and that is true of us individually and collectively, so we need others to expose our blindnesses and to increase our understanding of our humanity.

Parekh argues that liberalism is right to assert that there are universal moral principles (such as the rights of women, free speech and the right to life), but wrong to insist there is only one interpretation of those principles and that that is its own. Rights come into conflict and every cul ture negotiates different trade-offs between them.

To understand those trade-offs is sometimes complex and difficult. But no one culture has cracked the prefect trade-off, as western liberalism in its more honest moments is the first to admit. There is a huge amount we can learn from Islam in its social solidarity, its appreciation of the collective good and the generosity and strength of human relationships. Islamic societies are grappling with exactly the same challenge as the west - how to balance freedom and responsibility - and we need each other's help, not each other's brands of fundamentalism. If we are asking Islam to stamp out their fundamentalism, we have no lesser duty to do the same.