The Prime Minister is not short of things to pray for this Christmas. The continuing morass of Iraq, rebellion over top-up fees and the looming publication of the Hutton report - not to mention his health - all add up to a strong case for divine assistance. But Blair takes his religion more seriously than most, and shopping lists are not likely to be his style. Not since Gladstone has Britain had such a religious premier. Far from seeing prayer as a short cut to getting what he wants politically, Tony Blair sees politics as the means for working towards goals inspired by his faith. In a foreword to a book about Labour Christians, he wrote: "Neither faith nor politics can be simply about believing - it must be about action. Religious beliefs and political beliefs will achieve nothing until people are prepared to act on those beliefs."
This year, the Prime Minister appointed a "faith tsar", John Battle MP, to act as a bridgehead into the religious communities; said that he will answer to "my Maker" for his actions in Iraq; was evasive about whether he had prayed with George Bush; and established a faith community steering group to look at closer links between government and religious groups.
He is reported to have wanted to end a broadcast on Iraq with the words "God bless you", until the secular views of his advisers - a godless lot, by his lights - prevailed. All of which worries some of Blair's friends (who fear comparisons with Bush) and provides ammunition to his left-wing enemies, who see his Christianity as a further indication of his essential conservatism.
But just as religion is making modest inroads into politics, organised religion is host to momentous political struggles and factionalism, especially in the Anglican communion, which is riven by the issue of homosexuality. Ironically, Blair took great interest in the process of the Archbishop of Canterbury's appointment and great delight in Rowan Williams's elevation. As the Prime Minister apparently becomes increasingly religious, the primate is becoming a battle-hardened politician. The line between politics and religion is blurring on both sides.
It is clear that Blair's politics are a long way from those of the French revolutionaries who set out, in Diderot's phrase, to "strangle the last king with the guts of the last priest". But he is not alone in his faith. Gordon Brown is a preacher's son, which helps to explain not only his passion for social justice, but also his strong belief in the work ethic and individual responsibility. As his biographer Paul Routledge puts it: "He honestly believes that work is good for the soul, which should mean that his own is in no danger." David Blunkett, Paul Boateng and Tessa Jowell share some of their leader's faith - and there are plenty of junior ministers, such as Stephen Timms, Ruth Kelly and Stephen Twigg, with strong religious convictions. Keith Porteous Wood, executive director of the National Secular Society, has become worried enough to make the somewhat absurd claim that the "non-religious feel alienated and excluded from the political processes that help shape our society".
While Wood protests too much, a glance across the Atlantic suggests that Labour should be careful not to wear its religious robes too heavily. Bush, who has described Jesus as his favourite political philosopher, seems to personify the capture of American politics by the religious right. And figures such as John Ashcroft, the right-wing Christian attorney-general who tried to ban his staff taking part in a gay pride march, are truly scary. (That Bush had to play the liberal and overrule him on this issue says it all.)
It is fun to imagine to which biblical texts Bush refers before making his decisions. Perhaps something about camels and eyes of needles before the cut in capital gains tax? A parable on ploughshares and swords before Iraq? There is, however, one area in which his faith has probably been instrumental and against which few can argue: the $15bn for Aids victims in Africa.
But the dance between faith and politics in the US is unique. G K Chesterton described America as "a nation with the soul of a church", and moral-religious fervour has been part of its history since the war of independence. Although the religious right currently has the upper hand on issues such as abortion, it is worth remembering that what James Morone, author of Hellfire Nation, calls the "moral urge" has often come from the other side of the political spectrum. The campaigns against slavery and for civil rights - it was the Reverend Martin Luther King - were built on religious, moral messages.
In America, personal views on faith influence politics directly in a range of "hot-button" issues such as abortion, genetic research, gay rights and birth control - and indirectly, through the organising power of the southern churches. In the UK, in direct contrast, issues of conscience are typically legislated on through a free vote, in an explicit recognition that they are separable from run-of-the-mill party politics.
Yet in the US, religion and theology play little part in the political philosophies of significant leaders, or the philosophies which guide either of the main parties. Bush is a Christian, but his politics are pretty secular, based around the loci of money, power and votes. Despite US religiosity, the divide between church and state remains, in this philosophical sense, absolute. In any case, Christianity is a once-a-week religion: the rest of the time, the US worships at the altar of materialism. Theodore Zeldin caricatures the nation in Happiness: "In addition to being pagans, worshipping success in this world, Americans also adopted Christianity just as soon as it seemed to be fashionable, just to be on the safe side."
America is the only developed nation in the world where the majority of the population believes in the existence of hell. But there is one region of another country where hell-believers are still in the majority: Northern Ireland. And if the US is a special case globally, the province is a very special part of the UK. One of the reasons why the Reverend Ian Paisley is such a difficult politician is that he is not really a politician at all. Politicians engage in compromise, are capable of seeing limits and are able, to some degree, to move with the times. Paisley is not like this because he believes he is on a mission - that he ultimately serves not his constituents, but his God. On a different scale, the war against terrorism is hindered by the fact that the enemy is fighting not for a nation or special interest, but for divine reasons.
Paisley, Bush, hypocrisy and terrorism: good enough reasons, one would think, to build the highest possible walls between the worlds of politics and faith. The greatest gifts of the Enlightenment - individual autonomy and the rise of scientific reason - must be defended against the vagaries, absurdities and wickedness of religion. This, at any rate, is the view of thoughtful, progressive humanists such as A C Grayling in his latest book, What Is Good?: the search for the best way to live. Far from assisting religions through tax breaks - which the government is reported to be considering - we should withdraw public funding from faith schools, disestablish the Church of England and repeal all the blasphemy laws, Grayling argues. We should seek to "secularise society" and leave religion as a matter of private observance.
Grayling is most scathing about the "Babel of New Age religion and quasi-religion . . . often a pick-and-mix involving some tincture of astrology, feng shui, herbalism, and much besides (usually in short-lived bursts, between the shiatsu and the low-fat diet)".
But it is neither possible nor desirable to bring about such a sweeping secularisation. It is not possible because politicians are people, and people set their goals, at least in part, in line with their faith: so politics cannot be scrubbed clean of spiritual content. And from a democratic point of view, it may be the worst of all worlds for politicians to be forced to hide the religious motivations upon which they base their actions. We expect our elected representatives to describe the ideological foundations for their programmes and, to the extent that these have religious roots, we should know about them.
But even if it were possible to build Chinese walls down the middle of our public figures, it would be a mistake to turn away from religion entirely, even - or perhaps especially - for those on the left. This is for three reasons.
First, the delivery of policy requires engagement with the sources of authority, wherever they may lie. This naturally includes secular groups, but it also means working with religious organisations. New Deal teams often include religious leaders, and neighbourhood renewal schemes work better if they engage local community leaders, who are often also religious ones. This is likely to be the focus of the report from the faith steering group expected next month: its chair, Fiona Mactaggart, is the minister for race equality, community policy and civic renewal. (Blair may write the foreword.) And the Home Office community cohesion panel is due to report at a similar time, with undoubtedly a similar message.
The second progressive argument for religion is the power of religiously inspired ethics in the service of many left-of-centre objectives, especially social justice, poverty reduction and welfare. Robert Putnam, the US social scientist, argues that it is a mistake for the left to take a secular turn, because it deprives progressives of the capacity to denounce poverty and racism as not merely bad, but wrong - even sinful. Given that the moral ground remains salient in public discourse - and perhaps is becoming more so - it would be foolish to cede it to the right.
If these first two arguments have the feel of realpolitik, the third goes to the bones of the issue. Societies and economies require a pool of positive moral values in order to function. Progressive philosophers such as Gerry Cohen and Joseph Raz argue that modern societies, based on the freedom of the individual, need also to attend to their social forms, to their prevailing ethos. Cohen, a former Marxist, now believes that progressive change relies not on a vanguard of the proletariat, but on "moral pioneers" - those who challenge the status quo by the way they lead their lives. "Justice," he writes, "cannot only be a matter of the state-legislated structure in which people act, but is also a matter of those acts they choose . . . the personal choices of their daily lives . . . in the words of a recent slogan, the personal is political."
The British government is also increasingly worried about the "acts people choose", from antisocial behaviour to unhealthy lifestyles and a disengagement from politics - a trend unlikely to be reversed by the policy kite flown this month of lowering the voting age to 16. The existence of an antisocial behaviour unit at the Home Office is testament to the weakening of a value system that could be succinctly described as "love thy neighbour".
It is not necessary to go as far as the American writer A James Reichley, who argues that "republican government depends for its health on values that over the not-so-long run must come from religion", to see that society does need communal values, held dearly by most people, in order to function. And although it is not impossible to imagine secular wells from which these values might be drawn, few can be seen in real life. And values are what religions excel at.
This is not to say that all, or indeed, most of the values that have been historically propagated by religions are good ones. Across human history, religions have done better at encouraging fear, hate, xenophobia, war and authoritarianism. All too often, the churches and other religious organisations have supported the powerful rather than the downtrodden.
And recent shifts towards less liberal versions of faith are disturbing: the congregations that are swelling are of the evangelical kind, while the liberal wing of the Anglican communion is on the defensive. The perils of Islamic fundamentalism speak for themselves. In an era of great freedom, uncertainty, doubt and complexity, there is an obvious attraction to forms of faith that offer simple rules for living. Who wants to struggle with the dilemmas of sexual life, when an Alpha course can put you straight?
For religion to play the progressive role described, of underpinning fundamentally collective and sacrificial values, rather than fuelling hatred, theology needs a sharp dose of modernisation. With few exceptions, theologians spend their time thinking and writing about specifically religious issues - on matters internal to their faith - rather than providing religious perspectives on wider issues.
This is the evangelical weakness, too; reli-gion is of no value if it is concerned only with its own existence.
But the apolitical nature of theology has deep roots. During the early Enlightenment, the liberal countries where the most radical ideas were emerging were forced to separate theological from philosophical scholarship, in order to prevent civil unrest. In 1656, the States of Holland - where Descartes mostly lived and worked - issued a decree that secured the "freedom to philosophise", but not "to the detriment of true theology and Holy Scripture". This was achieved by declaring philosophy and theology to be entirely separate activities and banning philosophers from writing about biblical matters. Other nations issued similar compromise edicts.
The legacy of this 17th-century tactical division is with us still. Most of the theories and practices that guide modern life - in economics, politics and the physical sciences - have emerged from the "philosophical" side of the fence. Meanwhile, theology issues detailed studies of its own navel and has ended up as a kind of minority intellectual hobby. This is a loss both to religious thinking, which remains other-worldly, but more importantly to the rest of the academy, which would benefit from the nuanced and humane thinking that theological approaches can provide.
There remains, inescapably, a tension between individual freedom and traditional religion. As Grayling puts it: "In humanist ethics the individual is responsible for achieving the good as a free member of a community of free agents; in religious ethics he achieves the good by obedience to an authority that tells him what his goals are and how he should live."
But it is possible to see that free agents might choose, of their own volition, to submit themselves to the commitment, community and discipline of a particular faith. And it is likely that the collective benefits flowing from a widespread acceptance of certain moral sources allow us to lead better lives than in an atomised world of private morals. So long as these commitments are autonomously chosen, it is difficult to mount an Enlightenment attack upon it.
Fundamentalist, simple-minded religion is clearly much worse than no religion at all. And apolitical religion belongs in the dustbin. However, a religious structure and ethos that reflect individual liberty and engage with real-world issues may be better than a triumphant, market-mediated egoism. No one knows the answers to our biggest challenges, and no one should claim to. Religion, at its best, is a collective mechanism for people to help each other at least to try to formulate and pursue the right questions. In this sense, it is not so very different from politics, or at least politics as it should be, after all.