The best place to think about the future of religion, in my experience, is over a cup of coffee - or, to be precise, over a tall, semi-skimmed vanilla latte and a fat-free blueberry muffin. My local Seattle coffee bar is situated inside the Whiteley's of the Bayswater branch of Books Etc, which makes it, I suppose, a store within a store within a store. It's the sort of enlightened bookshop that allows coffee-drinkers to read books without buying them. I like to sit at one of the big black formica tables where the serious readers congregate; it means I can cast sneaky glances at what my neighbours are reading. And this is what always starts me thinking about the future of religion.
It's not that the Seattle/Books Etc customers read books about "religion", as such; the titles they choose come from sections as disparate as health, philosophy, cookery and new age. But exactly which shelf they come from is difficult to tell, for at least half the books slide from one subject to another: from cookery to health; diet to spirituality; fiction to philosophy; personal finance to ESP; skincare to Hindu chakras. And no, I haven't invented those last two. A week ago, someone left a book on the table called The Trick to Money is Having Some! which explains how disembodied thought-forms can produce financial windfalls. Only yesterday, the Middle Eastern woman next to me settled down to drink her decaffeinated cappuccino with a paperback called Absolute Beauty: radiant skin and inner harmony through the ancient secrets of Ayurveda.
My point is that even the most frivolous of these titles is evidence of a hugely important trend, one that could all but destroy churches and churchgoing in the new millennium. I'm referring to the search for the transcendent in the tasks and experiences of everyday life, which is itself a token of a more general disintegration of the frontier between the sacred and the secular. It's a sign of the times. The abolition of familiar boundaries is the crucial measure of the acceleration of the modern world; even the once crisp outline of modernity has faded away, leaving only the tantalising silhouette of postmodernism. Britain and Europe, town and countryside, high art and popular culture, news and entertainment, multinational corporations and governments: will these distinctions mean any more to our grandchildren than the difference between Calvinism and Arminianism means to us?
I'm exaggerating, of course, but when I visit Seattle/Books Etc/Whiteley's I can almost feel the tectonic plates grinding away under my feet. The books themselves cross the sacred/secular divide at many different points and in opposite directions. Maverick historians and scientists intrude mystical or extraterrestrial motifs into ostensibly non-fiction titles; innumerable therapies make a pitch for the soul; religious leaders dress up their prescriptions as practical self-help. Religion is far too restrictive a term for all this: what these products have in common is their attempt to make sense of the world and the self, a much broader purpose which also encompasses philosophy and science, religion's competitors. That's not how most theologians view the relationship between religion and science, but from my vantage point in Books Etc it seems blindingly obvious that they are fighting for the same customers. But perhaps the dichotomy is, after all, more imaginary than real. Don't the writings of Stephen Hawking and Richard Dawkins perform a sacred function, in the sense that they seek to unify the cosmos for an audience of the uninitiated? And as for all those books about UFOs, occult mysteries and miraculous therapies, might they represent not just a substitute for faith but the glimmerings of a new, privatised religion?
Even to ask these questions is to stray on to a battlefield. In the sociology of religion, one border which is not crossed often enough is that separating supporters and opponents of the secularisation thesis: that is, those who broadly accept Max Weber's vision of a progressively disenchanted world, and those who believe that, on the contrary, society is being re-enchanted. For secularists, flourishing Pentecostal sects and new-age therapies are the last twitches of a dying body; for the anti-secularists, they point to a new religiosity and perhaps a resurrection. In the end, however, the question is almost impossible to resolve. As Professor Joad would have said, it all depends what you mean by religion. In the century-old search for the perfect definition of religion, no one has ever managed to satisfy everyone: cast your net too wide, and you pull in Freemasonry and football; not wide enough, and most of Buddhism slips away. One way of escaping from this maze is to be air-lifted by the helicopter of modernism.
We are less worried these days by the bad habit things have of spilling over their definitional boundaries. Where modernism demanded tight definitions and ideal types, postmodernism is happy to note family resemblances. The modernist might ask: does our willingness to ascribe the word "sacred" to the Brazilian rainforests mean that we are becoming more or less secular? The postmodernist shrugs his or her shoulders and says, effectively, "whatever". Our new way of thinking about the rainforests might be important; nailing it down to a particular typology of sacred and secular isn't, not least because it can't really be done.
The good thing about this laid-back approach is that it allows us to make all sorts of unlikely comparisons. For example, I've noticed that Seattle coffee drinking bears a faint resemblance to religious ritual, what with the precision of the order itself and the competing rubrics of rival coffee chains: in the wrong establishment, describing a skinny decaf as "harmless" instead of "no fun" is tantamount to asking an evangelical vicar for the time of Mass. There's a seriousness to the whole operation which arises from awareness that both the tailor-made coffee and the coffee-bar-cum-bookshop are new social arrangements. The element of personal choice is crucial. It's as if people are saying to themselves: I'm going to take time out to drink the right coffee, and eat the right muffin. Seen in this light, the coffee break assumes a sabbatical dignity; it no longer seems strange to season it with the ultimate questions of existence.
This is not uncharted territory. This year has seen the reissue of Ira G Zepp's remarkable book The New Religious Image of Urban America, which argues that shopping malls have become ceremonial centres that usurp many of the functions of churches. Zepp, a religious studies professor from Maryland, bases much of his argument on the physical arrangements of malls: their use of crosses, circles and fountains to create a "camouflage of the sacred", a grand, exhilarating meeting place which makes suburban churches look mean and prosaic. Malls are a less important part of Britain's landscape but the analogy between religion and shopping is well worth pursuing, even at the risk of qualifying for Private Eye's Pseud's Corner.
I don't mean to say that shopping is a new religion; that is going too far. On the other hand, the transition from Sunday worship to Sunday shopping is unambiguous evidence of secularisation. Both churchgoing and shopping have been drastically affected by the conditions of late 20th-century life. Anthony Giddens has written about "the reflexive project of the self", a process of self-assembly in which people are free - and forced - to choose their occupations, friendships, political allegiance and religious beliefs to a degree that was unthinkable a few years ago. Choice and experience have gradually taken over from routine and belief - and this affects shopping as well as religion. In a world where the range of possibilities grows as the supply of free time shrinks, a boring trip to the supermarket is as much a wasted opportunity as a dull church service. Hence the search for the transcendent at Whiteley's.
I said earlier that the diffusion of the sacred throughout everyday life could destroy churches and churchgoing in western society. In fact, there is nothing inevitable about their destruction: the anti-secularists are right to suspect that the new social conditions could in theory sustain a religious revival. But the secularists are right, too, in pointing out that there is precious little evidence of it happening. On the contrary; a suffocating conservatism has become the defining characteristic of mainstream churches, distinguishing them from the vibrant, charismatic and experimental fringe far more accurately than any measure of doctrinal orthodoxy.
That conservatism takes the form, quite simply, of excruciatingly boring services. This is as true of Catholicism as it is of Anglicanism, or the Free Churches. My impression, based on decades of admittedly unscientific sampling, is that in three-quarters of Catholic parishes the liturgy and music fall below minimum standards of competence while half of all priests are unable to preach effectively. The dead hand of 1960s liturgical reform is partly responsible for this, replacing as it did the suggestive Tridentine silences with a badly translated vernacular which barely varies from one service to the next. This repetition is deadly, and what it kills is transcendence. Laity as well as clergy are implicated in this: all too often, parish life is dominated by an earnest elite of middle-aged professionals whose preoccupation with "Justice and Peace" does nothing to stifle the congregation's yawns.
The real problem with all the mainstream churches is that their modernity is so old-fashioned. They are modernist in two crucial respects: in the brutal simplicity of the aesthetic, and in their implicit belief in a grand narrative of political (as opposed to economic) liberation. What they are not, in any sense, is postmodern. The conventional churches fail every important test thrown up by fresh patterns of consumption and identity.
Take entertainment, for example. In the last couple of decades, daily exposure to professional actors, singers and presenters has raised our expectations of public performance to mercilessly high levels. Most clergy, in contrast, take high boredom thresholds for granted, sprinkling overlong sermons with pitifully weak witticisms. Or consider the break-up of traditional neighbourhoods, which has propelled people into a restless search for new forms of community and, especially, the intimacy of small groups. Most churches offer only Nescafe and small talk. Meanwhile, the growing complexity of life is transforming the way we worry, so that anxieties about health, appearance and spiritual destiny are no longer in different compartments. The churches fail this test, too, preaching a crude separation of body and soul. Finally, this generation likes things - even when it turns its back on the rat race, it is to buy chicken soup for the soul or an incense candle. For the mainstream churches, on the other hand, the only commercial transaction untainted by greed is a bring-and-buy sale.
But let us stand back from the traditional churches for a moment, and try to work out what a postmodern religion attuned to 20th-century cultural appetites might look like. It would lavish attention on music, for a start, and train its ministers in television skills. It would exploit new technology and address the nagging worries of its flock - from personal finances to addictions. It would provide instant friendship for the lonely and disoriented - widows, foreigners, students.
Does such a religion exist? It does, though most of us are too busy laughing at it to appreciate the magnitude of its achievement. Step forward the "happy clappies", the much-derided Pentecostal and charismatic Christians, whose numbers have increased from 90 million worldwide in 1981 to over 400 million today.
Explanations for this growth tend to fall into two camps. For traditional left-leaning sociologists, Pentecostal "signs and wonders" reconcile the urban poor to the inequalities of predatory capitalism; for the Pentecostalists themselves, it is all down to a move of the Holy Spirit.
But what is wrong with both these arguments is that they pay too much attention to message and not enough to medium. If we adopt a typically postmodern frame of reference, concentrating on how people believe rather than what they believe, we can see Pentecostalism in its true, postmodern colours. It is a religion of rock music, house fellowships, addiction counselling and even weight loss: these days no born-again bookstore is complete without a book telling you how Jesus can help you shed those extra pounds. It is also, of course, a religion whose frighteningly intense theology of salvation demands total commitment; but most of its adherents don't experience it in quite that way. The midweek house groups which form the backbone of the movement have a wonderfully intimate feel to them. Their members use the Bible in much the same way as recovering addicts use the 12 steps: to help them make sense of their lives, a day at a time.
And besides, it is quite possible to detach the medium from the message. I've just come back from the world's largest gay and lesbian church, the Cathedral of Hope in Dallas, whose ultra-liberal spirituality - in theological terms, as near a polar opposite as you can get to conservative Pentecostalism - is mediated through an eerily similar range of house groups, videotapes, counselling and so on, to say nothing of thrillingly fast-moving services. The implication is clear: it's not what you say, it's how you say it. Back in 1966, Peter Berger and Thomas Luckmann argued in The Social Construction of Reality that, given the right social conditions, any creed could be made plausible, even one built round the notion that if you eat raw fish you can talk to space aliens. Thirty years on, as if to prove their point, Mormonism is one of the world's fastest-growing religions - thanks, at least in part, to its prayer groups, videotapes, websites and so on. You get the picture.
Is this good or bad news for the mainstream churches? In theory, it is the best news of all, the good news of their salvation. Remember that Pentecostalism remains part of orthodox trinitarian Christianity; its radical accommodation to the way we live now has scarcely touched the doctrinal content of its faith. In theory, a Catholicism renewed by a postmodern aesthetic could popularise even those bits of papal teaching that liberal society has set its face against, such as the ban on artificial contraception. The same goes for any other declining denomination: if it can only make itself interesting and attractive, it will no longer be necessary to agonise over the details of theology. But I can't see it happening. Pentecostalism will continue to grow, but it can't be expected to mount a single-handed rescue of western Christianity. My guess is that, for the next decade or two, graphs of church attendance will continue to produce gradients steep enough to ski down, after which they will bottom out. Most of us will have to look elsewhere for our religion. Coffee, anyone?
Damian Thompson is the author of "The End of Time", published by Vintage in January at £6.99