Visual arts: A heaven lit by some very dim bulbs

The Liverpool Tate's exhibition undoubtedly has a Big Idea about celebrity and religion. Unfortunately, it's also Very Stupid.

Heaven is a contemporary art exhibition about religion and pop culture. This is the show that has the statue of Di as the Madonna that has provoked such a storm of controversy about whether or not it is controversial. Devised in Germany, the show had its first run in Dusseldorf before opening last week at the Tate Gallery in Liverpool.

It gets together all sorts of work, most of it not much good. It has art about Elvis and Michael Jackson. It has art about fashion and bodybuilding, about children and virtual reality and aliens from outer space. It has some not-quite-art too, fantasy couture and real-life star relics such as a bustier of Madonna's.

The show also has an argument; all this work has been gathered to present a thesis about religion in contemporary life. It seems to me a bad, stupid argument. But then I'm not sure if it's meant in earnest. An air of jokiness pervades the exhibition, though it's hard to say quite what the joke is about.

The show's subtitle - An Exhibition That Will Break Your Heart - sounds like a joke, a knowing nod at the blurbs you get with blockbuster novels and movies. And the point seems to be that this is not an exhibition that will break your heart, but which - on the contrary - deals in emotions to which the viewer is expected to feel superior.

Then, as you go upstairs to the Tate's top-floor gallery, you pass signs saying "You Are Approaching Heaven", and that's another joke, or bit of jokiness, emphasising that we are not really approaching heaven. And a visitor leaflet, written by the director of the Liverpool Tate, takes up the strain: "Dear Visitor," it begins, "Welcome to Heaven."

So while this is a show about religion, it is immediately hedged about by hints that we should not take it too seriously. Perhaps this is wise. For now the argument begins, and it's not a promising start. "Heaven," the leaflet continues, "is a name we give to our heart's desire." I don't think so. For this claim must mean something like: if my heart's desire is - say - to have a little cottage in Devon, then for me, that is the equivalent of what a Christian - say - means by Heaven. Indeed.

But the argument goes on. Religious belief has declined. The religious impulse has not. It has just moved on, and now we worship other things (the coercive/inclusive "we" does a lot of work here): "Celebrities, supermodels and pop stars are now idolised as once were saints and angels, while their clothes and props have become devotional relics. Physical perfection is suffered for and valued more highly than spiritual perfection. Glory has become glamour, innocence has become youth, virtue is money and paradise is a beach holiday."

You could not think this unless you thought that whatever fascinates, enthuses and obsesses people qualifies as a religion (there is, of course, no cult of Di anyway). And you could not think this unless you thought that, prior to some unspecified date when religion declined, everyone was unstintingly pious and never gave any attention to worldly values (although the fact that religious preachers have often strongly denounced such values suggests otherwise).

So the guiding idea of this show is one you could expect to find in a completely disposable journalistic think-piece, an argument which collapses on a moment's examination, and which - in a newspaper - is of course only designed to detain the reader for that moment. Whereas this art exhibition must have been a very complicated and expensive thing to organise, it asks an hour or two of you time, it runs for months - and all the while it's sustained by no more than a bit of mental fluff headlined "Celebrity - Is It the New Religion?" or whatever. It seems disproportionate.

And the more depressing thing is that this thought is not the usual curatorial guff. It is what much of the art in the show thinks too. When Jeff Koons does a flawless, polychrome effigy of Michael Jackson and a cuddly monkey, that's his point. When Mariko Mori presents a computer-generated artificial leisure paradise, it's hers too.

The show is full of pieces that boast a Disney-meets-Baroque aesthetic, that evoke religiose kitsch and the twee sublime, that graft the faces of Leonardo di Caprio and Kate Moss onto religious paintings, that equate VR with the world beyond. (The fit isn't always so neat: Gilbert and George's "Underneath the Arches" living sculpture routine is included for the absurd reason that it "echoes the steps of the medieval St Vitus's dance".)

Memories here are extremely short. The whole show is a long-winded footnote to Andy Warhol's gilded, iconic portrait of Marilyn Monroe. And looking a little further back, you'd have thought that the prime and obvious case of mass devotion in recent history was not Elvis or even Valentino, but Man of the Century Adolf Hitler. I suppose a show organised in Germany might not wish to dwell on this point.

But Hitler wouldn't do for another reason. The whole plan of this show is to say, not only that all worship is really religious worship, but that there are no distinctions to be made between worthwhile and unworthwhile objects of devotion. Some people like the Blessed Virgin Mary. Some people like Di. Some people are martyred for their faith. Some people are martyred for personal beauty (the French artist, Orlan, whose work consists of having endless of plastic surgery on herself, is included).

The presence of Hitler would naturally make this attitude harder to maintain. Or rather, it would disrupt the show's basic jokiness, its deeper cynicism. For I haven't put it quite right. You, the viewer, aren't truly meant to agree that Elvis or aliens or the perfect body are worthwhile objects of worship. No, the thought process that's encouraged here is in fact even more stupefying. You are meant to recognise - easy enough - that these are pretty dumb things to give your life to. But then comes the twist: hey, let's face it, like it or not, don't we all? That's what religion is now. The global media, you know, and its image world. It's taken over all our heads, hearts and souls. We may not want it, but we can't help it, so we may as well admit and affirm our helplessness.

The attitude is the old Warhol ethic, that of the volunteer zombie. The jokiness is a nervous snigger of knowing collusion with powers presumed to be beyond one's control or resistance. This is not a specific blasphemy against any established religion. It is a general and most disgusting blasphemy against the human mind.

Heaven, Tate Gallery, Albert Dock, Liverpool L3. Until 27 Feb. Closed Mondays. Admission pounds 3. concs pounds 2