Dinos and Jake's big joke

The Chapman brothers' human mutations aren't about anything except their own futility. And they comfort and terrify by turns.

Dinos and Jake Chapman's sculpture causes mild disgust, has perfect finish, and often makes people laugh. Most of it uses shop- window dummies, which the artists interfere with drastically. All this makes it media-friendly. But is it any good and does it have anything to say? The short answers are: yes and no. The longer answers are an art journalist's quagmire.

Cybericonic Man, currently hanging upside down from a ceiling in the ICA, may be their best work to date. It has something in common with a previous work, bermensch, their model of Stephen Hawking in his wheelchair and placed on a rock. This piece has never been shown in Britain and the brothers complain that press photographers always snap it with its dry ice machine switched off. bermensch and Cybericonic Man have personalities, unlike most Chapman humans, who tend to be permutations, specimens. These two are heroic.

Hawking is Hawking, pitiful and noble in his post-quantum, post-accident glory, and Cybericonic Man is a martyr. His skin is silver, except where chunks of his flesh have been cut off. His wounds are red. He stands, weight on one leg, a cool Saint Sebastian. His hands are tied behind him to a post. He is on a silver plinth on the ceiling, and his long black hair hangs down. He is an upright statue, but his torture involves being suspended: he's an artistic failure, a ridiculous aesthetic resolution of something. From his wounds he drips fake blood, which trickles down his body and splashes into a bucket. It runs back up a plastic tube with the aid of a pump, the noise of which fills the room. He is a Marvel Comics hero and a Jeff Koons gone wrong. Renaissance, futuristic, and a verbal quip: buckets of blood. He is utterly absurd.

He is also rather beautiful, which most Chapman sculptures aren't. He is the complete realisation of an idea in a little boy's mind: a boy who has a model and wants to torture him. And for some reason he wants him to be sci-fi, so he paints him silver. Such is the Chapmans' art. Their sculptures are art-jokes, rather than any other kind - not jokes about desire, or genetics, or Freud, or any other subject their pieces raise in discussion. Drawings are turned into solid objects. The idea, "let's make it into a sculpture", seems so crazy it's irresistible.

With Great Deeds Against the Dead, a large work of two years ago, they remade a Goya etching, reworking it using mannequins. It was a close-up and blow-up of their previous Disasters of War, in which plastic toys were re-modelled into a tabletop version of Goya's famous series. Now Great Deeds has been succeeded by Year Zero, a Garden of Eden-ish scene with three naked, playing children taking the place of the three mutilated men of Deeds. No wounds this time, except one cut knee. No genitals either, and this from the artists whose representation of their mother - Mummy Chapman - was all genitals: penises and vaginas appearing like disease all over her body. But this adds up: in Mummy Chapman, and in the sexual world of the Chapmans' work in general, there is a kind of sterility. Testicles and breasts are not much in evidence. One of Mummy's nipples is a vagina.

But interpretation is an endless exercise. Of Year Zero Dinos says, "I think we've been quite generous with this piece," meaning that it's wide open for different readings. I give them mine: it's a variation of Great Deeds, but appears to show an event prior to it. It is about infant sexuality, despite the missing genitals, about jouissance. The naked children disporting themselves on a tree somehow lead to the atrocities Goya depicts. They look at me and smile. "Everything we do is completely open-ended," says Dinos.

So is it any good, their art? Well, yes. It's all well-made, it sticks in the mind and it is a little disturbing. And it provides icons for your thoughts to wander around: it has, in other words, and like other art, that Rorschach ink-blot quality, although its nature is more that of a psychological guided missile. It is about the impossibility of anything ever being perfect. This seems like a valid idea, and whenever you think about the impossibility of things being perfect, the Chapmans' pieces may pop into your mind as useful visual meditations. In this way you will be both comforted and terrified - that's what art's for. This doesn't mean the Chapmans put those ideas in there, but they do know you will be able to get them out. Of course, there is something depressing about this, something hollow, which may make you feel you hate art. Either the brothers knew this all along, or they have latched on to the idea. They talk about futility.

For the first time they have made an installation, Tragic Anatomies. The walls are sky blue, the floor is artificial grass, there are mounds and fake shrubs, turning a room into a park. The electric twilight is harsh. The only sound is of a dry-ice machine. Hiding in the bushes are Siamese twins, and occasionally triplets or quadruplets, fashioned from the trademark mannequins. They are all children and nearly all girls. In one, four heads join at the throat, faces pointing inward and upward. In the centre where they meet is an anus. It's horrible. Two girls have a third, upside down, between them, her legs waving in the air. Another is a kind of centaur with a figure on her back, who clutches the penises that emerge like horns from the centaur-figure's head. All look as if they had been transformed during an act of sex, punished by being eternally joined. The whole has a numbing circularity about it.

"The Siamese twins," says Jake, "are like something mathematical. I always see these things as like Sol Lewitts." Jake's favourite artists are Carl Andre and Sol Lewitt, whose sequences - different ways of drawing lines, or boxes - have a sublime spuriousness about them. Meaninglessness, endless variation and "knowing about futility and not being frightened of it": we talk about such things and Jake says: "I would like someone to make that interpretation. No one has done so far." It seems as good as any. Do they feel that they want to control interpretations of their work? "No." And: "Our interpretations are as deluded as anyone else's."

Cybericonic Man is more interesting than Tragic Anatomies because, having a personality, he implies a story. And despite all our talk of futility and endlessness and Samuel Beckett and Sol Lewitt, this more traditional approach may yield more possibilities than all the Siamese variations in the world. But all Chapman pieces are fantasies - "hallucinations" - made huge and perfect. They get to you, one way or another. I was looking forward to seeing their show at the ICA, wasn't disappointed, and look forward to the next one. It's enough.

n 'Chapmanworld' continues at the Institute of Contemporary Art, The Mall, London SW1, to 14 July (0171-930 3647)