In the sweet hereafter

Pop, the monarchy, television, banality... though the overfamiliar soft targets of contemporary culture often appear in Mark Wallinger's work, his most effective pieces offer serious reflection on religion and the afterlife.

In this time of tightly focused soloists, Mark Wallinger is a one-man band. His mid-life retrospective at the Liverpool Tate Gallery is packed with works, and such different kinds of works, about such a mixture of things, that in describing it I can't help skipping plenty. But I can give an idea of the range. The artist is in his early forties. During the last 10 years his work has included:

In this time of tightly focused soloists, Mark Wallinger is a one-man band. His mid-life retrospective at the Liverpool Tate Gallery is packed with works, and such different kinds of works, about such a mixture of things, that in describing it I can't help skipping plenty. But I can give an idea of the range. The artist is in his early forties. During the last 10 years his work has included:

* A racehorse, purchased, named A Real Work of Art, trained and raced, the jockey in the suffragette colours of green, white and violet (a memorial to Emily Davison, who threw herself under the King's horse at the 1913 Derby).

* A hosepipe that ran from inside an empty art gallery and passed through its window to trickle feebly onto the pavement, entitled Fountain (after Marcel Duchamp's urinal, but pointing to the utter ineffectualness of art's "transgressive" gestures beyond the gallery).

* A life-sized, ie, a very small, statue of a man in a loincloth, placed on the empty plinth in Trafalgar Square, entitled Ecce Homo (a reference to Jesus Christ at the moment when he's presented for public judgement).

Each of those works was an outdoor piece, and each worried at art's ability to make contact outside the art world. Wallinger's art is always self-conscious. At the same time, it's very keen to get stuck into matters which aren't just arty.

His approach to medium is quite unpurist. This Liverpool show has paintings, photos, sculptures, videos. There's a lot about English history, culture (high and popular) and politics, with treatments of Stonehenge, the Union Jack, Tommy Cooper, immigration, the 1966 World Cup, panto, the monarchy, the turf, Shelley, George Stubbs, the Beatles. And if that check-list suggests the partly familiar territory of lefty cultural critique, then there's also work which thinks seriously about religious (Christian) belief, about dying and going to heaven, a line of interest practically unparalleled in contemporary art.

This exhibition has the overall title Credo - a good cue, because Wallinger's work at first could hardly look less credulous. Whatever the subject, there's always a strain of knowing waggishness, and a penchant for cunning tricks - mirror images, slow-motion, things played backwards, repetitions, puns, palindromes, and all kinds of self-reference.

The devices of detachment; but everyone does detachment. The question is, what for? Sometimes for not much more than a smart, pointed gag. In Passport Control, six photo-booth photos of the artist (big specs, shirt and tie) are graffitied-over in felt-tip into a gallery of racial caricatures. He appears as a Jew, an Arab, a Chinese, an African, a Sikh, and finally a caricature of himself, the specs and necktie heavily inked over - and the effect is both to mock stereotypes, and (the cheerful absurdity of it) to mock sensitivity about stereotypes too.

Sometimes it's more the way of deadpan hatred. Royal Ascot sets four TVs in a row, and shows simultaneously the coverage from four successive days of an Ascot week, at the point where the royal party arrives and drives past in their carriages - identical events, identically filmed, the only variation being in the costumes worn and the TV commentators' slavish descriptions of them. It becomes an entirely fascinating spectacle, and - beyond the ritual and sycophancy - a Groundhog Day study in habit. See the Duke of Edinburgh spontaneously point out someone in the crowd in exactly the same way four days running.

The videos are the best things. They can get much more involved. In Hymn, a man (the artist again) stands on a soapbox on a London hill, the sky behind him. He holds by a string a helium balloon, with a little boy's face printed on it (his younger self, you may guess), and there's a cylinder of helium on the ground beside him, from which he inhales regularly to get a squeaky voice as he sings through the verses of a Victorian hymn:

"There's a friend for little children

Above the bright blue sky"

At the end of which he lets the balloon fly away.

You might suspect that this is just an elaborate mockery of a bit of sentimental/cynical Victorian consolation - something it's pretty easy for us to mock. But notice, it is very elaborate, this performance with its relay of themes: heaven, sky, helium, lighter than air, high voice, balloon, childhood. It's too much for sarcasm. It's like a Heath Robinson psychological exercise, a literal and laborious scheme for recovering one's losses - being a child, believing in heaven. The squeaky charade is ridiculous, but the sense of loss is felt.

But sometimes all you can see of the feeling explored is the barricade round it. In another video, Angel, the artist appears as a blind man, with dark glasses and tapping white stick, walking to stay on the spot against the direction of a moving escalator in a London Tube station (Angel, of course), as he recites in a weird voice the opening of St John's Gospel. "In the beginning was the Word." It's weird because actually he is saying the words phonetically backwards, and then the whole film is shown in reverse. Finally he stops and is carried back up the escalator to the chorus of Handel's "Zadok the Priest".

The feat and theatre of it are impressive. But with its log-jam of devices, the work becomes like a sentence with too many negatives in it. Moving in order to stay still, mouthing words whose sense is beyond you, simultaneously ascending and descending, blindness - blind faith? blind to faith? - the effects pile up into vagueness. Er, something to do with religious belief... But at bottom, there's the true observation that London Underground escalators are a bit of everyday Dante.

That sort of observation, relatively uncluttered with tricks, is the making of my favourite piece in this exhibition, Threshold to the Kingdom. An airport. The camera is pointed straight at the automatic double doors of International Arrivals. The doors swing open, travellers appear in ones, twos and groups, pass through, over and over. The film is slowed down so they become specimens for our contemplation. The soundtrack is the ethereal chorale of Allegri's "Miserere". The central conceit is evident: arriving at an airport, arriving in heaven.

But the great thing is how strongly the comparison strikes, and how it brings to intensity, makes sense of, all those unfocused airport feelings. The arrivals gate is not just the point where your safe landing is finally confirmed (survived the flight, got through customs), but the point where you return to life, emerge into consciousness after the suspended limbo of air-travel; and also where you find yourself momentarily disoriented in this new place, and making an involuntary public appearance before the waiting crowd, and always half hoping to be "met", even when they know there's no friend there for you. The emotional identification is so sharp that when some uniformed flight staff stride through the doors, your first thought is: angels!

In Threshold Wallinger gets the most valuable form of detachment - a true thing made. You can look at this work without thinking at all of the artist behind it. As art goes now, that's rare credibility.

Mark Wallinger - Credo: Tate Liverpool, Albert Dock, Liverpool L3; to 23 Dec; closed Mondays; admission £3