Lucian Freud: In a class by himself

The exemplary retrospective of Lucian Freud at Tate Britain might have been expected to establish his work in the great tradition of Western figure painting. In fact, says Tom Lubbock, it reveals him as an artist in deliberate retreat from it

Lucian Freud is our greatest living painter, or so people say, to cheer themselves with the thought that there is still such a thing, that the great tradition of Western painting has not stalled, but is alive and well and working in west London. But to take Freud, now 79, as an Old Master in our midst is to mistake his work, to make it something general and exemplary, rather than what it is, something singular and strange. Freud paints the human figure, face and body, and his art may, of course, be compared with the figure painting of the past. It should not be confused with it. It stands elsewhere.

The big Freud retrospective is curated by William Feaver, and it is exemplary: in the choice and ordering of work; in the fact that – despite the Tate's addiction to interpretive verbiage, and despite all the biography lodged in Freud's work, bursting to be spelled out – there is not a label or caption in sight. It is pictures, 60 years of them, all through. But something Feaver said the other day about Freud's work seems to me to capture exactly what it isn't.

A very large painting from 1996, of a monumentally fat woman asleep in an armchair, her face pressed into her palm, was (he said) about anyone who has ever gone to sleep in the 20th century. Allowing for hyperbole, that's the kind of resonance you might well look for in Freud's work. It sounds like Rembrandt. It invokes the traditional ambition of human figure painting to carry large, universal, public meanings. But it isn't how Freud operates, and the epic scale of this picture, its clear sense of public address, is sheer dissonance.

Dissonance is a common experience in Freud's mature work, in the pictures he began making from the start of the Sixties, when he moved from the brilliant nervous pin-point illustrational style of his first success to the painterly, fleshy, thingy, tough-and-tender rendering that he has held to (with variation) ever since. Dissonance – because these paintings are always hinting at categories in which they do not in fact belong. And it is a good question to ask simply: what are they of?

The scene, for a start. What is the recurring situation Freud paints? A bare room, with bare boards, plastered walls, an iron bed, mattresses, a ripped leather couch, a sink, inhabited by men and women clothed and naked who sit or lie about, sometimes with dogs. Some stark existential theatre? No. This room isn't meant as a room in a house, these scenes don't come from anybody's life, there's no story. Compare Munch's Puberty. A troubled naked girl is sitting on a bed. This we understand as a girl in her bedroom, at a particular moment in her life. But Freud's figures are just there.

Of course we know where we are. It's an artist's studio. Brushes, piles of wipe-rags are sometimes prominent. But it isn't a neutral environment, just a place where the painting occurs, and which may happen to appear (as in Euan Uglow's work, say). This particular studio is undeniably present and to be recognised as itself. The studio set-ups, often highly artificial, are presented without pretence. When two or more figures appear, they are never really in a relationship. They have lives, but not here in the picture. They are here to be painted.

And who are these people – individual sitters or anonymous models? Are these works portraits, or are they "life studies"? Well, the figures are conspicuously individuals, they have individual faces, they have (no less) individual bodies, closely particularised. But these are not portraits in the usual sense of a picture that establishes a self, a character, a life. The figures are desocialised, deselved, taken out of their clothes, out of their places, out of their bodies even. The long steady poses that Freud's painting requires make body-language dumb, neutralises all performance. His sitters are beyond self-presentation.

There is no eye-contact with the viewer ever. Faces are averted, and often hidden. Or if not, then gazes are averted. And even when, rarely, the gaze is turned front, it is never fixed on us. These figures are looked at, but they do not look back, and their look cannot be returned. The view is intimate, but impersonal. And still they are clearly individuals. And we know that they are generally people known to Freud, lovers, wives, children, friends, mother. So there is a suggestion of something like portrayal, but deeper, getting beneath the self to a more basic truth; or perhaps rather an art that – remarkably – separates off the physical singularity of a body from any sense of personal identity.

How does Freud treat bodies? That's the main disputed issue of his art: cruel or kind, violently mastering or lovingly attentive? We all know what Freud doesn't do. He doesn't idealise. But as for what he does do... Certainly this isn't a painting of methodical observation, like Giacommetti's or Uglow's, taking readings, making carefully measured marks. But nor – his advocates always insist – is it caricature (like Otto Dix, say) or expressionism (like Schiele). And the insistence is needed, because evidently Freud's painting is far from cool. It has attitude. It uses a kind of distortion.

It has an undiscriminating eye. We normally treat bodies hierarchically. We see some parts of them, the face first then the hands, as soulful; and painting gives them special treatment accordingly. Freud treats all body parts as equal. The face, the foot, the genitals, the knee, each are a thing to be delineated. This is another dimension of Freud's impersonality. Or, to put it more strongly, dehumanisation. It is how one might look at a corpse, a body devoid of the living body's centres of interest.

And as well as undiscrimination, there is plain exaggeration. Obviously Freud's bodies look done over, beaten up, raw, bruised, braised. Every bump and swell, every variation in skin colour, is brought out, has the contrast turned up on it, so that these become bodies whose pain is easy to imagine – and at this point you may start talking about mortality, or misanthropy.

But Freud's bodies are uncertain. In some ways they are so physically present. Every detail of their concavity and convexity, their folds, sags, veins and wrinkles are observed. The paint is physical too, thick, sluggish or staccato, making its way bit by bit across the body's terrain, smoothing nothing over, registering each stone, rut and puddle on the journey. And Freud's apparent distortions may only be a by-product of his emphatic inching attention.

And yet in other ways his bodies are insubstantial. Nothing seems to touch anything. There are a thousand points of contact, feet on ground, body on bed, body on body, limb on limb – but contact is hardly made felt. The bodies have mass. But they have no skin, or weight, or pressure, and often no articulating skeleton. They seem, at times, very strangely put together. And this is an effect of Freud's closely observational procedure. He doesn't take bodies whole, as integrated organisms, as solids in space. He takes them part by part.

What's the idea of a Freud picture? Not a story, not a person, not a figure even, but an arrangement of human and animal elements and furniture and props within a picture frame. The poses are said to be the models' own. But the angle of view (often from overhead) and framing are the artist's, and he has done extraordinary things with this vocabulary. But at the same time the pictures never quite live with their limitations. Other ideas and ways of meaning – symbolic-looking objects, hints of relationships between figures, of a conscious pose or an inner life, or of surreal narrative (such as legs poking out from under a bed) – make incongruous appearances. The exclusions nag, as well they might.

Freud in his time has been both praised and blamed for pursuing figure painting against the dominant current of modern art, as if nothing had changed. But he has not done this at all. Every aspect of his painting responds to what has changed. It performs a radical reduction of the art, declaring a withdrawal to the private space of the studio, to a subject-matter largely restricted to the contingencies of personal acquaintance, to a tight-focused relationship between the eye and the body before it that puts aside the great traditional repertoire of human-figure meanings. Sometimes Freud paints beautifully and sometimes coarsely, but the moral of his mature art is constant. Heads down for survival.

Lucian Freud, Tate Britain, Millbank, London SW1, £9 (Advance tickets: 0870 166 8283; www.tate.org.uk). To 22 Sept