Marked for ever by a brush with life

Seen any good art lately? I have. Philip Guston, at the Royal Academy. Piccadilly. London. Opposite Fortnum and Mason. I recommend that you approach it at a leisurely pace, say via the Burlington Arcade where you can have your shoes polished by a flunkey in livery and maybe pick up a cashmere cardigan for the man or woman in your life, then pop across to Fortnum's tea rooms for a Welsh rarebit and English cordial. Make a treat of it.

A truly great retrospective of an artist few of us know very well doesn't come along that often. A painter, to boot. A painter who isn't Picasso or Titian, or Andy Warhol or Jackson Pollock. A painter who isn't either abstract or figurative, but neither and both. A painter in whom every important 20th-century argument about art seems to have been enacted. Reader, go. And if you don't skip through the Royal Academy's fountains on your way in to see Philip Guston, I guarantee you will skip through them on your way out.

I have an axe to grind, I don't deny that. Nothing personal. I never met the man. Nor do I have Guston canvases in my cellar whose value I suddenly see the opportunity to augment. No, if you're looking for a motive look to age. As I grow full with years, so do I grow to love the years in others. Give me an aged genius before a young one any time. And let's keep raising the bar. If I live to be 100 it will only be 100-year-old artists I admire.

A wonderful provision of nature this, to forestall the cultural equivalent of paedophilia, that is taking an inappropriate interest in the doings of people younger than yourself. I'd enshrine it in law myself, and have the police maintain a register of offenders. Such and such a one has been seeing hovering around young persons' art. Keep an eye on him.

Not that Guston made it to a grand old age. He was a mere 67 when he died in 1980. And not that he wasn't brilliant when he was a boy. Aged 17, he could knock you off a Picasso cum de Chirico cum Piero della Francesca worthy of a knowledgeable and accomplished artist twice his age, and this while doing a cartoonist's course in his spare time. Six or seven years before, his father hanged himself in frustration and disappointment, a fugitive from Odessa whose life had not turned out as he would have liked it. Not every migrant's story is a happy one. Not even if you're Jewish in America.

The young Philip Guston found the body. Such an event can speed up artistic development. Whatever the reason for his precocity, or its impressiveness, it's the evidence in Guston of its opposite - a quality for which words like culmination or ripeness or consummation seem to close more than they open - that is really exhilarating: prolificity in your pensionable years, creative abundance when you are meant to be getting feebler, not so much late as persistent, unabating florescence, and let death go take a jump.

All credit to the Royal Academy for hanging this show so that you follow the painter's evolution, stage by stage, room by room, anticipating development and change all right, but nothing on the scale of what's waiting for you - boom! - when you suddenly enter the grand scala showing Guston in the full bloom of his 60s, one spectacular canvas after another, grotesque creations, now depicting the painter as a potato head, one eye for ever open like a camera shutter, unblinking whatever the horrors; now depicting him bound in a terrifying spider's web, bleeding crimson paint, while the giant insects advance on him as though he's good for nothing but their dinner; and now depicting him buried in his bed, grown into his wife, a huddle against the black immensity which engulfs this heartbreaking little everywhere, the painter's insect hands outside the coverlet, still grasping the brushes.

Always the brushes. This is art at its most serious, made by someone for whom it was impossible not to paint or to go on thinking and talking about painting. Talk. One of the best paintings in the show is called simply Talking, and shows the painter's hand holding a smoking cigarette - always a cigarette - and maybe a smoking brush - always a brush - nothing more, just the hand painted like a gun, with a hint of rolled-up sleeve, and a one-fingered cartoon wrist-watch, but never have you seen such garrulousness evoked, as though the hand is the most voluble organ we have.

It was in Guston's case, most certainly. Though he was a great reader and talker, a devourer of ideas against which he was for ever testing himself, unforgivingly most of the time, as though in despair that as an artist he was not more of a match for them, it is nonetheless the paint, applied intimately, three inches from the canvas, which does his talking for him.

He'd tried silence. For a while, in the bloodless 1950s, he'd been the all-American abstract expressionist, shimmering away in seas of luminous quiet, a hero of pure feeling, until he gave all that away in a fit of noisiness. "I got sick and tired of all that purity," he said. "I wanted to tell stories." Not everyone forgave him that. Some saw it as a betrayal. In fact, he'd been the noisiest, most figuratively fraught abstract expressionist there ever was; it was just that the quiet ones hadn't noticed.

What came next, his famous hooded clansmen, candy-pink and puffing Groucho Marx cigars, sometimes murderous in their anonymity, sometimes just perplexed and sad, like baffled Jewish migrants from Odessa, and sometimes brandishing Guston's own smoking paint brushes, are masterpieces of the grotesque. Wonderfully gluttonous works follow, in which seeing, talking, thinking, eating, smoking, suffering, joking do not so much compete for the artist's attention as entirely constitute it. This is what it is to be alive.

Reader, go. Before the forces of quiet finally claim you too.