As a historian who is paid to look at the past, I find myself frequently indulging in rants about how we live in an anti-historical age, where history is not taken seriously. Typically, of course, I am referring to those who are so absorbed in the perpetual cultural flux that is consumerism that they have little time for the past, given that `the past' did not contain such life-essentials ad I-Pods, MP3 downloads, Botox, and Big Macs. For a society whose economic stability largely depends upon easy credit and the buying and selling of consumer goods, the past is generally a hindrance. Tradition, for example, is seen to serve in such a context simply to limit and restrict creativity; only as the past can itself be turned into a commodity - whether a mock-Victorian snuff box from Past Times, a special-effects filled documentary on Ancient Rome from the History Channel, or a tourist attraction such as Trooping the Colour in London - does it appear to fulfill a useful social function.

Glancing at a typical catalogue of Christian goods, it seems self-evident that the church in all its branches has cottoned on to consumerism in a significant way, whether in the slick marketing of big conference speakers or the selling of iPods with ready-loaded sermons and lectures. Use of modern technology and modern consumer idiom is not necessarily a bad thing, of course: what would have happened to Luther if he had not had the printing press? Or if he had not become, quite literally, the first modern pin-up? No popular appeal, no mass dissemination of his ideas, no theological reformation. And the use of computers, internet, even savvy marketing, can be of great benefit in spreading the faith, with the important proviso that we ought always to appreciate that media are not value-neutral and need to be used in a reflective and self-critical manner.

There is, however, a more insidious anti-historical dimension to some parts of modern Christendom: nostalgia, that uncritical adulation of the past, nay, that invention of an idealized past, which legitimates all manner of criticism of the present, and yet which really provides no answers but rather simply an excuse for inactivity.

Nostalgia is, of course, not the preserve of Christianity. In the fourth century, there were plenty of Roman pagans who saw the problems in the Roman Empire in terms of the arrival of Christianity as a new religion. It had displaced the old gods and, more importantly, the old values which had made Rome great and thus led the empire into social chaos. Today, of course, historians can give a perfectly adequate account of Rome's imperial crisis in terms of material factors relating to economics and military logistics; but at the time, nostalgia provided the lens through which the present was examined and by which Christianity was condemned.

Nostalgia is not an entirely bad thing. It often has a useful function for those who are getting old. I remember my grandparents reaction to news stories of mass unemployment, of rapes and of murders: `Well, I wouldn't want to be young today' they would say, as they changed the TV channel. Yet I always found myself wanting to respond that, when they were young, a whole generation of British youth were annihilated on battlefields in Belgium and France; there was then the mass poverty of the 1930s; followed by and then the butchering of six million Jews in the Holocaust, not to mention the Blitz and the military casualties of World War Two. My father's earliest memory was of running with his mother to the air raid shelter, hoping that he would not be blown to smithereens; mine was of playing with my father in the park. That has to be an improvement. Given the choice, childhood and youth in the seventies and eighties was, for me, relatively comfortable and quiet, with little more than the result of rugby internationals and cricket tests about which to worry.

For my grandparents, such nostalgia was harmless enough; perhaps a way of comforting themselves as they grew older and saw the power and vigour of the days of youth slipping slowly away. But nostalgia can be very sinister indeed. It has, after all, played a powerful function in the development of some highly reactionary and malicious political creeds. Fascism and Nazism both played heavily upon an idealized notion of a past society that was essentially feudal in its basic shape. Mussolini played on images of the glories ancient Rome in order to legitimate his political program in the present; and Nazism self-consciously built much of its propaganda upon several centuries of German imperial identity, from Frederick the Great to Otto von Bismarck, to present itself not simply as offering Germany a glorious future but, most importantly, as offering a fulfillment of Germany's glorious past. The same, I would suggest, lies at the root of many of those political movements which, for good or ill, play upon a strong sense of national identity to fuel their political programs. Nostalgia and fascism so often go hand-in-hand.

And then we come to the church. Religious people, especially orthodox religious people, are almost invariably nostalgic: whether it is Eastern Orthodox looking back to the Fathers, or Catholics looking to the Middle Ages, or Reformed looking to the Puritans, such can so often look back on history and find there the ideal world that they are looking for today. The past provides them with an idiom to express their disgruntlement with the present, and yet, like those who sought for the historical Jesus, they so often stare down the well of time and see their own reflections gazing back up at them. For me, by contrast, it is very hard to be nostalgic about a world with no anti-biotics, no electric lighting, and no flush toilets; but then I always try to see the big picture and take into account material factors, and not just the theological textbooks that are being written at any given moment. Given that my ancestors were social nobodies, it would also have been a world where I would probably never have learned to read or write and have been worked to death by the time I was forty.

Nostalgia can thus be nauseating, especially in a church context. Indeed, as a historian, one of my major concerns is to disabuse students of any nostalgia towards the past which they might have, and this not for the sake of cheapshot iconoclasm but because nostalgia, in church life as in cultural politics at large, can simply end up as a justification for an uncritical status quo, whether the nostalgia is the straightforward kind promoted by the right or the more subtle kind promoted by the left.

On the right, one does not have to look very far in the American church world to find those who will use a nostalgic view of the past to justify all manner of things, from what amounts to basic racism, to reducing the lives of modern women into little more than baby production (`pop 'em till you drop' theology, as the wife of one minister friend describes it), to promulgating sub-biblical views on everything from culture to the state. Such apparently reactionary attitudes might seem radical in their implications - often in the US these views are cast as a protest against a putative modern social liberalism which has undermined core, and previously unquestioned, values. Christianity thus becomes primarily an idiom of cultural protest against the present; but the net result is, ironically, that the status quo remains in practice unchallenged because history becomes simply a Manichean battleground, where a mythical past serves simply to underline the general mediocrity of the present and the special status of a few; and is thus not useful as a source for constructive confrontation of and engagement with that present.

On the left the picture is no better: whether its emergent Christianity or Celtic spirituality, the pick 'n' mix attitude to the past is a classic example of the imperialism of the modern present combined with the aesthetic sensibilities of consumerism. For both groups, history is really only useful as a source of precedents for the present; and the recovery of history is simply the highly selective appropriation of those bits of the past which meet with approval and fit the world we want to make - or justify - for ourselves. Interesting, isn't it, that none of the current emergent/evangelical love for the Fathers involves the appropriation of the brutal anchoritic and ascetic practices which so marked the piety and theology of ancient Christianity. If, as the advertising blurb for one conference implies, patristic Christianity is the first example of emergent Christianity, then emergent Christianity should really be heading out into the Utah desert to engage in brutal self-abnegation, not holding swanky gatherings in plush metropolitan hotels and conference centres. I suppose Augustine did, in the words of scholar, Robert Marcus, pave the way for `mediocre Christianity' which had a space for material comfort and ascetic under-achievement; but, ironically, for many on the left, Augustine is the one real bad boy in the patristic era.

So how should Christians approach the past? A tough question and one which needs a longer answer than I can offer here. I would suggest, however, that any proposal needs to take three things into account. First and foremost, Christianity is not rediscovered or reinvented every Sunday. The Christian faith has been around for some two-thousand years; and Christians today stand in continuity with that past. This must always be acknowledged and never sidelined: respect for the past is not only appropriate; it is also necessary.

Second, Christians need to rid themselves of what historians often refer to as the Whig interpretation of history, one of the key characteristics of which was the tendency to examine the past in order to find anticipations of the present. To ask questions such as `Was Montanism an early example of Pentecostalism?' is to indulge in the privileging of our time over all others. Yes, this is where and when we live; but we do not have the right to assume all history finds its meaning here and now. History is useful as much because it speaks to us of times, places and ideas that are different to our own as for any analogy or precedent we might find there.

Third, we need to be grateful that we live in the present. Many of us have much for which to be grateful, from antibiotics to the wonders of modern communication. Only as we shed our nauseating nostalgia (or, perhaps better, naustalgia) will we become truly active for the spreading of Gods kingdom in the present in the way in which God intends. We should not waste our time waiting for the present to turn back into the past; we should seize the day and do that which we have been called to do right here and right now.