´The body beautiful´ Craig Raine The Guardian

The story so far. In 1997, at the Royal Academy, the sensation of Sensation: Young British Artists from the Saatchi Collection is neither Damien Hirst's increasingly dowdy, dilapidated, dog-eared shark, nor the homeopathically talented Tracey Emin, whose empty appliquéd tent is an exact objective correlative of her camp conceptualism. Nor is it yet Marcus Harvey's cool, ironic but cynically hyped portrait of Myra Hindley, whose compositional method is denounced by the tabloids - because the face is an agglomeration of childish handprints. Nor is the sensation of Sensation the Jake and Dinos Chapman 1995 fibreglass frieze of girls - naked, prepubescent, wearing only trainers, but sporting several penile noses and open, anal mouths.

Among this clamorous, attention-seeking art there is good work - by Jenny Saville, Rachel Whiteread, and the photographer Richard Billingham. And there, on the floor, 3ft long, is one indisputable, obvious masterpiece - a single work, the understated Dead Dad by Ron Mueck, the Australian son-in-law of Paula Rego - a calmly brilliant sculpture which is the contemporary equivalent of, say, Holbein's subtle portrait of Erasmus, with its engaged intelligence and wryly amused thin mouth.

The greatness of Dead Dad is oxymoronic: its very completeness also tells us something is missing. The sculpture dispassionately records every delicate and indelicate bodily detail - detail that is alive with accuracy. Nothing is missing. Tendons, toenails, the direction of dark hair on the calves, the hazy pubes a little stationary mirage, the tidy greying hair, the polished, modest, uncircumcised cosh of the penis at four o'clock, which echoes the thumbs across the open, upturned palms.

And yet this body is unmistakably dead. It is laid out - the opposite of foetal. We are not in the presence of sleep. The eyes have it - significantly pink, fatally, infinitesimally sunken. And the helpless hands have irretrievably lost it.

Everything is there still, but stilled, and something central has gone. The reduction in scale somehow suggests this loss. The body is lesser than life - for some, lighter by 21 grams, the weight of the soul: the alleged difference in body weight before and after death.

I talked to Ron Mueck in October 2000, when he was artist in residence at the National Gallery, and we discussed Dead Dad. He was worried about sentimentality: "I didn't really get on with my father but, as I made the piece, I found myself thinking about him, caring." The carefulness of his creation is cognate with care in the broader sense. In fact, sentimentality is nowhere in sight. Though there is sentiment - a completely other thing - it is inextricably fused with another perfectly proper, strong human emotion: curiosity.

Mueck also said that in creating Dead Dad he had worked from memory and imagination. Imagination. In the Lucian Freud retrospective at Tate Britain in 2002, no 113, The Painter's Mother Dead 1989, was a drawing done from "life", in the immediate aftermath of death. It records unsparingly the palsied skew death inflicts on the mouth. Karl Kraus said that a portrait was a picture in which the mouth was wrong. In death, all the mouths are wrong. The rictus is an oddly painful, unexpected, ugly fact. The undertaker and about 12 hours restore malleability and undo the damage. You have to be at a deathbed to know this. Mueck wasn't - and so couldn't be expected to know and record this expression of fleeting melodrama. Dead Dad isn't harmed by this omission.

In fact, on balance, the sculpture perhaps benefits - because Mueck's art is characteristically understated. Not for him the swastikas and hypodermics of, say, Bacon's painterly histrionics. His preferred reference work is Professor R D Lockhart's Living Anatomy ("A Photographic Atlas of Muscles in Action and Surface Contours"). This dislike of emotional grand guignol, of grandstanding exhibitionism, is at once typically Australian and classically modernist. Natural taciturnity meets principled artistic restraint. The modernist enquiry into the emotions is predicated on a shared scepticism about the purity and force of what we feel - Eliot, Joyce, Lawrence, Conrad, Camus, all know that we frequently feel less than we are supposed to feel. Or feel it differently. Or adulterated with "inappropriate" feelings. The modernists know, too, that in literature real but unspectacular emotions - like embarrassment, curiosity - are often ousted by super-sized emotional simplifications.

In the new Edinburgh exhibition, there is a piece called Spooning Couple: two tiny figures, a man in a T-shirt and a woman in a pair of knickers, cuddle up to each other like spoons, both facing in the same direction. They are bigger than a pair of spoons, more like Brobdingnagian salad servers. One's initial assumption is of cosiness and affection. There isn't any obvious antagonism of the kind recorded in Paul Muldoon's poem Asra, where a couple "wake before dawn; back to back: duellists".

And yet ... all is not well. They are not as comfortable, as relaxed, as they seem at first. Both sets of eyes are open - without eye contact. They are thinking. In silence. About what? We can only guess. Her unclothed torso is turned away from his clothed torso. His naked lower half is against her knickers. The T-shirt is unironed, its white muted. The knickers are somehow indeterminate - the faded colour purple that results when whites get washed with items which aren't colourfast. Romantic it isn't.

Vladimir Nabokov once asked his protégé, Alfred Appel, how academe was weathering a period of widespread student unrest in the 1960s. Appel reported that things at his university were quiet: a nun had complained that couples were "spooning" at the back of lectures. Nabokov pounced: "You should have told her to thank God they weren't forking."

Mueck's Spooning Couple are definitely not forking. They seem not to be spooning either, in the erotic sense - they resemble kitchen utensils in close proximity, more than they resemble human beings about to make love. Mueck has given us the habit of affection, the pose of cuddling. In Dead Dad, he gave us the mystery of death - of to be and not to be. In Spooning Couple, he has given us another mystery - the precise moment of sexual evaporation. The emotion here is as miniaturised as the figures - mild worry, "How did we get here, if this is where we are?"

Mueck has now created, by my rough calculation, about 35 pieces in nine years. There are no failures. (He spoke in 2000 about the pressure of success: "You have to keep on doing something better. Reviews stop you working for two years.") Only one piece is actual size - a dog: "The only lifesize thing I've ever done." I saw the photograph, not the sculpture: the dog was prognathous, either naturally, or as a display of aggression. It had a tiny, volcanic, red, pointed semi hard-on. The others, whether scaled up or scaled down, are equally painstaking.

And, in every case, the emotion is as accurate as the physical detail. Ghost, an early piece on show at Edinburgh, is a wonderful, unexaggerated sculpture depicting an emotion rarely noted by artists - self-consciousness. A gigantified girl in an unflattering swimming costume arranges herself awkwardly - as if she were a tripod rather than a biped - caught between two states, at once pathologically ordinary and a freakish refugee from Diane Arbus's lurid, unforgiving, prying lens. Her size, the scale, is how she feels about her body. Technically, this cognitive dissonance is called anosognosia - which means not being aware of your condition. She thinks she is the Incredible Hulk. She is only sick with shyness.

Art historians tend to source Mueck's art in the art of the past - particularly since his residence at the National Gallery - either in dialogue or in debt. The absence of originality is seen in some strange way as a guarantee of worth - and a vindication, therefore, of the art historian's role. Hmm. Mueck's sculptures are meticulously "copied", meticulously imagined and meticulously composed - like all the greatest art of the past. They share these demanding fundamentals. But that is all. Take, for instance, Rogier van der Weyden's Deposition in the Mauritshuis in The Hague. Two things immediately strike me. The blood from the wound in Christ's side runs down, disappears under his loincloth, and continues down his leg. Imagination. The man holding Christ under his arms has folded back his fur sleeves, so he isn't hampered, or soiled. Imagination. The right sleeve nearest to the viewer is painted so that we can see the open fur at the fold, which is like a wound. That visual echo is deliberate artistry.

Now consider a piece from 1998, Man with Shaved Head. It frequently provokes in critics a "comparison" with the Kritian Boy from the Acropolis (c.480BC). You might equally summon up The Dying Gaul (c.230BC) from the Capitoline Museum in Rome. Neither is properly pertinent. For a start, they both have hair, and it is crucial to Mueck's sculpture that his young man is bald. Why? Because the compositional axis of his sculpture is a parallel - between the circumcised head and shaft of his penis, and the neck and shaved head. Both bulbous paralleled spheres are themselves between two parallels - the cock is between the ankles (he is squatting), the skin-head is between extended arms.

Echoes. Parallels. In Man with Shaved Head, the very idea of parallels is suggested by the man's parallel feet and the parallel arms. Naturally, this is part of Mueck's sculptural stock-in-trade. He spends, he told me, a lot of time staring at his clay models - trying to see them. "If you've been looking at a piece of clay for hours you can't see it." He has invented strategies to counter this blasé blindness: he takes photographs; he looks at the piece in a mirror; he glances over his shoulder. In one case, Big Man (2000), he lost his rag, bashed it on the head, and created a frown from which the sculpture really began. Look for long enough and parallels - natural parallels - will mob the real artist.

For example, the cover of the National Gallery catalogue is a photograph of Mueck's tool board - pliers, pincers, punches, wire-cutters, all suspended from Phillips screws, handles dangling like legs, outlined in crayon on the plywood. There is also an outlined Mueck sculpture of a small baby - its legs an obvious parallel, but an ironic parallel, because its vulnerability also insists on dissimilitude.

Another example, Pregnant Woman (2002), demonstrates lucidly how the face and the body can be mirror images of each other. All portrait painters know - if they are any good - that the face is echoic, a rhyming dictionary. The eyes and the nostrils and the eyebrows are examples of almost competitive mimicry. Raise an eyebrow, arch a nostril - snap. In Matisse's 1914 drawing of Elsa Glaser, the mouth is another eye. In Mueck's Pregnant Woman, this network of parallels is extended to an invisible omnipresence.

First things first. You are overwhelmed by the size of the piece. She is larger than life - 8ft tall. But pregnant women at this stage are larger than life. There is, too, something unbelievable, impossible even, about their anatomy. Mueck reminds us of more familiar truths as well. The woman has monumental legs and feet. We think of women as feminine, delicate, waisted. And they are. But they are also female, sturdy and monumental. Pregnancy reveals the practicality of the pelvis, like the frame of a rucksack.

Then you are overwhelmed by the detail. Amazingly. The danger of scaling things up, of bigging it, is that there isn't enough detail to go round the acres of extra space, of dead space. Her calves and shins are shaved. There are two very inconspicuous spots on her bum - in exactly the right place. The spot on her left buttock is just to the left of her bum crack. The moles are perfect, especially the larger one just above her left armpit.

Then the parallels kick in: the closed rounded eyelids are mini-breasts, the nose a pregnant belly (with a mole placed to echo the bud of the navel). The lips and vagina are an obvious implicit parallel, of course. Her hair parallels her pubic hair - both wonderfully accurate, differentiated textures. Her arms mirror her legs, her hands mirror her feet.

Her look is one of exhausted, weary concentration. Her eyes are closed. The sculpture is a portrait of fatigue. This is typical of these unsentimental sculptures. Mother and Child shows a mother who has just given birth. The baby's colour is deeper, darker, shiny as brawn, say, turned out of a butcher's mould. Its umbilicus vanishes up the vagina. The vagina is echoed by the baby's buttocks and feet, from which the other end of the umbilicus protrudes. The woman's facial expression is neutral, bled of melodrama. Just looking, in Updike's phrase. There is no obvious joy, no tears. She is unsmiling. But the real triumph is the woman's hair - uncombed to exactly the right degree.

I said there were no failures. Perhaps there are - on the studio floor, in the rubbish bins. But I will enter a tiny caveat: some of the larger-than-lifesize masks run the risk of caricature. There are two in the Edinburgh exhibition: one a self-portrait of Mueck sleeping (Mask II, 2001-02), the other a black woman's plump face (Mask III, 2005). Of these two, the self-portrait runs the greatest risk, as did the original frowning self-portrait (Mask, 1997), which Mueck explained away by saying it was how he imagined he appeared to his children. Still, we are dealing with greatness here - no question.