ART / Radical chic and the schlock of the new: Andrew Graham-Dixon finds old ideas dominating shows by new artists at the Saatchi and Serpentine Galleries

ALL YOUNG artists know that to make their mark they have to be different. They have to break with tradition, challenge the stale conventions of the past, redraw the parameters of possibility. The trouble is that, although the message once sounded invigorating, a century and more of avant-gardism has given it the dead ring of cliche. Other ways of being an artist have to be found.

Two exhibitions in London at the moment, 'Young British Artists II' at the Saatchi Gallery, and 'The Barclays Young Artists Award' at the Serpentine Gallery, demonstrate how hard it has become for young artists to boldly go where no painter or sculptor or installation or performance artist has gone before. Neither show is likely to be remembered as a milestone in British art, but they do have unintentional significance. Their hidden theme is the predicament of the would-be avant-garde. Call it the crisis of originality: everyone wants to be original, but so many forms have been tried and tested already that genuine newness has become increasingly difficult to conjure. The collective motto of the late 20th century may turn out to be 'It's All Been Done Already'.

The postgraduate students short-listed for the Barclays Young Artist Award attempt to cope with the problem in a number of ways. The most significant solution - although it also makes for the least engaging art - is provided by Glenn Brown, one of only two painters included in the exhibition. In painting, more of everything has been done already than in almost any other medium. Brown deals with this knowledge by putting his own sense of belatedness and despondency to work.

His primary target in this enterprise is Frank Auerbach, who does double duty here as authority figure and sacred cow. Brown repaints Auerbach's cityscapes and portraits from illustrations of them in books, and exaggerates the contrast between his own slick photo-realism and the dense, clotted quality of Auerbach's originals. What you end up with is Auerbach without the impasto: Auerbach minus the expressionist rhetoric of endlessly reworked, hard-won imagery that is so much a part of his art.

The pictures make their cruel point. Auerbach's piled-on paint implies deep creative agonies, yet its appearance can be duplicated. Expressive originality, truth to the urgings of the inner self, can be feigned. But in contemporary art's hall of mirrors, Brown himself is even more vulnerable to criticism. By staking his own claim to originality on an attack on someone else's claim to originality, he is being deeply unoriginal. The appropriationist 1980s were overpopulated with artists whose subject was the art of other artists: American painters like Sherrie Levene and Philip Taaffe have long specialised in painting dumb copies of other painters' paintings. The picture-of-a-picture is an established genre. It's Been Done Already. (And it wasn't that interesting first time round.)

The crisis of originality is really just one variation of another, larger crisis: the crisis of radicalism. One of the great received ideas of the 20th century is the notion, enshrined in art- school culture, that it is the sacred duty of every artist to be radical in some way, whether it be political or philosophical or merely technical. So artists anxious to discover every unmapped corner of radical thought and gesture have made art out of more or less everything that art was once supposed not to be made out of. When everything has been done, all that remains to do is to do it again. And the result is necessarily odd: art that looks radical but cannot actually be radical because its language has been depleted by over-use; academic radicalism; conformist radicalism.

In a culture dedicated to novelty, precedence begins to count for everything: it is not the depth of the idea that matters, but the fact that no one else had it before. This is why (to pick just one example) Laura Thompson's work at the Serpentine Gallery can seem both elegant and terribly thin. It consists of a film of the artist painting simple patterns on the white walls and floor of a studio. The shapes Thompson paints are circumscribed, for the most part, by her physical reach: a circle painted to the largest circumference a single movement of her arm can manage is typical. This is painting reduced to its most primitive form: a memorial to the body that produced it, a souvenir of physical rhythms, painting as gesture alone. But although the gestures are executed with a kind of balletic grace, that is small compensation for the fact that this form of painterly reductiveness has been practised many times before. Art of this kind is peculiarly diminished by deja vu.

The legacy of radical avant-gardism left to today's young artist is broken: this century has seen the fracturing of the older traditions of painting and sculpture into shards of minute innovation. This was done in the name of liberation and expressive freedom, but its consequences may have been less liberating than the rhetoric of radicalism made out. Most of those tiny fragments, because their iconoclastic charge derived so often from such a small, single alteration to the texture or content of the work of art, have proved deeply resistant to development or enrichment by subsequent generations of artists. It is in the nature of any radical gesture that it should lose its power with repetition. Once the act of painting has been reduced to the single rhythmic gesture - well, that's it. The gesture itself is not that interesting: it is the idea that it once represented, the challenge that it once laid down to the tradition of painting, that made it seem worthwhile.

Thompson and Brown are only two young artists in a modest exhibition of postgraduate art and their work is perfectly competent. The point is that their art is not unique in its unsatisfactoriness, its quality of a cul-de-sac prematurely arrived at, but entirely representative. The world is full of young artists who have chosen to colonise this or that tiny corner of once-novel painting or sculpture only to find that it is barren territory. The culture of radicalism is ruled by the law of diminishing returns.

'Young British Artists II', at the Saatchi Gallery, contains some worthwhile art (by Rose Finn- Kelcey, in particular) but is more significant in this context for the bad art that it contains because it is so revealingly, symptomatically bad.

Marc Quinn's chief contribution to the exhibition is a cast of his own head made by pouring nine pints of his own blood (collected over time) into a mould and then freezing it. Preserved on a plinth inside a purpose-built freezer cabinet, it looks less horrific than it sounds: you need to be told that it is made out of blood for its unpleasantness to work. It seems probable that this is the first time such a gesture has been performed by an artist, so Quinn can at least claim to have risen above the crisis of originality. But outlandishness can't make up for witlessness. The head-shaped plasma ice-lolly has novelty appeal, and that is about it. Profound claims have been advanced for it as sculpture for the Aids era but, if anything, that makes the work even less engaging. So it isn't even enigmatic: its oddity is hedged round with worthy social concern.

The Saatchi show reveals the extent to which moral worthiness or theoretical self-justification have come to be regarded by many younger artists as substitutes for quality. Never mind if your art is dull and incompetent: as long as it is relevant and politically correct, you are on safe ground. Sarah Lucas and Mark Wallinger are the chief torch-bearers for this particular form of mediocrity. Lucas contributes several silk-screened, blow-up reproductions of double-page spreads from the Sunday Sport; Wallinger a series of large paintings of thoroughbred stallions owned by Sheikh Mohammad, exhibited under the collective title Race, Class, Sex. Lucas's pictures are, on a technical level, dull reprises of Andy Warhol; Wallinger's are pedestrian pastiches of Stubbs. But that is not meant to matter, since this is art as stimulus for seminar-room discussion.

Lucas's and Wallinger's pictures exist to raise topics: sexism in the media; the equine symbolism of wealth, power and dynastic continuity (something like that, anyway). But what they really represent, in perhaps its most depressing form, is the crisis of radicalism.