Sam Harris is a young philosophy graduate from Stanford University who was completing a doctorate in neuroscience at UCLA while writing this, his first book. He tells us it grew out of "a long essay... produced in those first weeks of collective grief and stupefaction" immediately after 11 September 2001. His argument is that the threat of terror facing the world is the direct result of religion — or, more specifically, faith itself. If we are to defeat terror and survive as a species we must find a way to bring about "the end of faith", for faith itself "is surely the devil's masterpiece".

Harris is at pains to make clear that by 'faith' he does not mean merely vicious fundamentalisms. He divides 'people of faith' into extremists and moderates. The danger from extremists is obvious enough but the moderates, Harris's prime target, are "the bearers of a terrible dogma: they imagine that the path to peace will be paved once each of us has learned to respect the unjustified beliefs of others". He aims to show that "the very ideal of religious tolerance... is one of the principal forces driving us towards the abyss", because a liberal and moderate tolerance unwittingly inhibits the reasoned critique of intolerable irrationalism.

Unhappily, the argument rides on the back of some startling oversimplifications, exaggerations and elisions. For example: "A glance at history... reveals that ideas which divide one group of human beings from another, only to unite them in slaughter, generally have their roots in religion." In support, he cites the conflicts in Palestine, the Balkans, Northern Ireland, Kashmir, Sudan and so on. That religion as a badge of tribalism is frequently a major complicating factor in such conflicts is obvious, but it is by no means self–evident that religion is invariably the root cause. Republicans and Loyalists in Northern Ireland have not been killing each other over transubstantiation or the priesthood of all believers. Control of land and resources, racial animosities, cultural rivalries and secular ideologies, as well as religious differences, give us our potent mix of reasons for blood–letting.

And even if we did concede that Harris has produced a plausible list of conflicts more or less rooted in religion, what about the world wars of the 20th century? Did British and German empire–builders slaughter millions in the 1914–18 war for religion? Was the conflict between liberal democracy and Nazism a religious war? Did Stalin kill tens of millions of his own people for religious reasons? Yes, says Harris (as indeed he must to support his thesis): communism, and presumably fascism, was "little more than a political religion[...], cultic and irrational". But this is to concede that it is irrational dogma in general rather than religious faith in particular which creates the killing fields, and that undoes his argument.

Harris's conviction that religious faith itself is the root of all evil, and that in a world of suicide bombers and WMDs we can no longer tolerate its existence, leads him to a dark but logical conclusion: we must bring faith to an end. How? is the question that is crucial and not really answered. "Some propositions", he proposes,"are so dangerous that it may even be ethical to kill people for believing them[...] There is, in fact, no talking to some people. If they cannot be captured, and they often cannot, otherwise tolerant people may be justified in killing them in self–defence. This is what the United States attempted in Afghanistan, and it is what we and other western powers are bound to attempt, at an even greater cost to ourselves and to innocents abroad."

So Sam Harris the faithless and George Bush the faithful, equally stupefied by 9/11, arrive at much the same conclusion: there is an enemy out to get us. It can't be argued with, so it must be eradicated at whatever "cost to ourselves and to innocents abroad".

Is this, then, a worthless book? Far from it. It is engagingly written and its arguments challenge even where they shock or fail to persuade. Woven into the main theme are stimulating reflections on consciousness and 'spirituality' — a term he uses frequently. He undermines his war on unreasoning faith with the admission that "we cannot live by reason alone", and he looks to psychology and neuroscience to demonstrate that "we need not be unreasonable to suffuse our lives with love, compassion, ecstasy, and awe; nor must we renounce all forms of spirituality or mysticism to be on good terms with reason". Such sections seem to come from another book, perhaps reflecting Harris's current interest in neuroscience. They sit strangely with the deadly rationalism which would exterminate what he insists on calling 'faith'.

For this is the problem with The End of Faith: we all have faith of one sort or another. In a world which seems incapable of shaking off belief in real gods and devils, it takes a lot of faith to be a humanist. And, paradoxically, to believe it is actually possible to bring about "an end of faith", whether by killing the faithful or by bombarding them with moderation, surely requires even more faith than that required to move mountains. Faith "on good terms with reason" seems a more moderate goal, and Harris's next book, when he has got over his "collective grief and stupefaction" at what Allah's holy warriors did to the twin towers, should be worth waiting for.

The End of Faith is available from Amazon (UK)