Big shows are strange things, big shows of big painters stranger still. By and large, we come to an artist's work in dribs and drabs, a couple of pictures in this museum, half a dozen in that. To see 70-odd of one artist's paintings in one place at one time is a different experience altogether. When that artist is Francis Bacon, a man given to working on a grand scale – typically, triptychs each of whose three panels may measure 6ft by 5ft – the risk of overkill is high. Add to this the fact that every one of those panels has the gravitational pull of a dying star, and you might reasonably ask whether a big monograph exhibition is really the best way for the Tate to celebrate Bacon's 100th birthday.
To which question the answer is an unqualified "yes". One thing we all know about Bacon – one of the many things – is that he was a ferocious self-editor, given to destroying his work in fits of drunken self-loathing. When, nearing 50, he moved to the Marlborough Gallery, its infamous owner, Frank Lloyd, curbed these bouts of canvas-slashing by having his chauffeur pick up works from Bacon's Reece Mews studio before their paint was dry. As a result, for good and ill, there are many more late Bacons than there might have been, and their quality is commensurately patchy. The Tate's curators have done the artist a great favour in radically trimming his oeuvre, although 70 is an awful lot of Bacon even so.
The question, really, is what we learn about the artist from seeing him in this way that we wouldn't have learnt from a smaller, more focused show. The answer, unexpectedly, is his painterliness.
With the exception of Andy Warhol, Bacon comes bogged down with more anecdotage than any modern artist I can think of. There are more soi-disant Friends of Francis than there are fragments of the True Cross. Stories about him abound and (their subject having been a gleeful mythomane) are often untrue. The beatings, buggery, boot-blacked hair, the Colony Room witticisms – "Champagne for my real friends! Real pain for my sham friends!" – all encourage us to see his pictures as artefacts rather than as art. As a result, it's easy to forget Bacon the master painter.
Accordingly, Tate Britain's curators have hung their show in rough chronology and by occasional theme, but with little in the way of biographical prompts. The resulting blur of popes, Soho denizens, dead boyfriends and sides of beef allows us to look past the what of Bacon's work to the how – to the brilliance of a man whose feel for the brush was uncanny, whose understanding of colour liturgical. You are left to find your way around this show less by thought than by feel – a useful approach to the art of a man who saw human life as essentially instinctive.
Bacon's own feel for texture is astonishing: not for nothing was he mesmerised by that great master of cloth, Goya. The tweed jacket of Figure Study II in the show's first room may pay homage to Magritte's bowler-hatted men, but its hairiness is animal rather than human. The grey drapery folds of Study after Velazquez (1950) have both the solidity of corrugated metal and the flimsiness of chiffon. They conjure up a space – one of Bacon's famous boxes – only to deny it, reading at once as background and foreground and as neither. To see this painting of a pope merely as a response to the Vatican's collusion with fascism in the Second World War is to belittle it. Bacon's interest in evil is generic rather than local. The spatial ambiguities of his works are there to shift their meaning from the specific to the general.
What is particularly striking about the Tate's instinctive and sensuous approach to Bacon is the way it allows us to follow a small number of great preoccupations through his career. Man with Dog (1953), on loan from Buffalo, organises space into three, Rothko-ish fields of colour. Three rooms and 20 years later, Triptych, May-June 1973 seems altogether different in its technique, scale and subject; and yet it, too, works in increments of three – a trio of panels, and of colours (black, buff, oxblood) within those panels. Both works also show three-dimensional spaces pre-flattened out into two dimensions. (Bacon worked from photographs, some of them in this show. His canvases are pictures of pictures.) In 1991 as in 1947, Bacon's battles of brutality are fought in an arena uniquely his own, in an unknowable world between worlds.
Francis Bacon died in 1992; unbelievably, the last major retrospective of his work in the UK was held in 1985. His place as the greatest British painter of the 20th century seems secure, and yet the truth is that stories don't age well. In the centenary of his birth, it is worth recalling him as something more than the central character in Love Is the Devil – more than a maker of gay art or absurdist art or existential art, more than a 20th-century phenomenon. I can't think of a better 100th birthday present than this, a show whose scale allows us to see the scale of its subject; a man whose theme and whose genius lay in instinct.
Tate Britain, London SW1 (020-7887 8888), to 4 Jan 2009
Need To Know
Francis Bacon's life was, as he said, lived "between the gutter and the Ritz". The son of horse-rearing Anglo-Irish gentry, his taste for sadomasochistic gay sex was legendary: the two great loves of his life were George Dyer (who Bacon claimed to have met when Dyer was burgling his flat in 1964) and John Edwards, the illiterate East End tough who inherited his £11m estate. In these sweepings from London's social floor, Bacon found confirmation of a belief that coloured his art: that life was as brutal as it seemed, but that brutality had a beauty of its own.