Essay: Paint away, Paul: you're a real post-modern renaissance man

As part of the first London Festival of Literature, I spent the other week as a writer-in-residence at Saatchi & Saatchi. Knowing that Salman Rushdie, Fay Weldon, Peter Porter and William Trevor (among others) worked in advertising early on in their careers, I'd anticipated that there might be the odd aspiring writer lurking in the Creative department. What I hadn't anticipated was the sheer number of people, from all parts of the building, coming forward with novels, poems, plays and screenplays. Some of their work was highly accomplished. They didn't seem to know the great unwritten rule of British culture: that you're allowed only to Do One Thing.

Paul McCartney doesn't seem to know this rule either, though nannyish critics will soon remind him. Initial responses to the news that the former Beatle is about to exhibit 70 of his paintings were respectful enough. The exhibition, it was emphasised, will be a modest affair, in Siegen, near Cologne in Germany, not the metropolitan glitterbash it could have been had McCartney exploited his fame, his friendship with Willem de Kooning, and the art-dealer family connections of his late wife Linda. It was also pointed out that McCartney hasn't had to pay anyone for the privilege - some people have been known to fork out thousands of pounds to have their work shown in central London galleries. The artist himself also struck a pleasingly tentative note: "I am not out to show the world what I can do ... I'm not trying to impress anybody except myself."

But already, more acid comments have begun to eat into the picture. Artist Michael Daley, given a sneak preview, wasn't impressed: "It is as if he wants to be fashionably abstract but accessible at the same time, and as if he is trying not to look like a conventional amateur painter." The art critic Brian Sewell deplored the "infuriating tendency among clapped- out old pop stars to become artists ... They usually produce unmitigated garbage and should stick to what they were doing ... I don't think anyone can move into the visual arts at that age [McCartney began painting at 40] and expect to be taken seriously."

There'll be plenty more where this came from when McCartney's show opens later this month. He'll be advised not to give up the day job. He'll have his lyrics used against him in headlines: Help! Nowhere Man. Get Back To Where You Once Belonged. Let It Be. Whether he's good, bad or indifferent as a painter isn't the point. He should have stuck to Doing His Thing. His offence is to have tried to Do Something Else.

Many other artists and performers have broken this rule. John Lennon did with writings and drawings, The Who's Pete Townshend with a book of short stories. Keanu Reeves and Johnny Depp are film stars who want to be rock stars. Clint Eastwood and Jodie Foster are actors more interested in directing. Dennis Hopper, actor turned director, also takes photographs. Anthony Burgess wrote symphonies, and hoped for posthumous recognition as a composer. Those who've painted, instead of minding their shop, include Winston Churchill, D H Lawrence and Paul Johnson. But the rule remains. The British are particularly keen on it. Perhaps that why Paul McCartney has chosen to Do His Other Thing in Germany.

Of course, there are good reasons to be sceptical when somebody famous for one talent chooses to flaunt another. The narcotics of celebrity induce dreams of grandeur, the illusion that I Can Do Anything, whereas art of whatever kind takes time, patience, practice, craft and graft. You can't run it as a sideline. You can't just switch your assets between accounts. Owning a voice fit to sing arias or read the news, or a body perfect to model dresses on, doesn't qualify you to write a bestselling novel, despite what publishers tell you and the money they'll pay you to find out. For most of the human race doing even one thing well is a struggle - and artists are human too.

But some people are born polymaths, and others find polymathy creeping up on them. My poet friends and I once dreamt of being poets and nothing else. We should have seen that we couldn't afford the luxury. What we couldn't have seen is how the other kinds of writing we took on to pay the rent or fill the time between poems - plays, novels, biographies, libretti, songs, television documentaries, children's books - would offer their own challenges and excitements, would add to our idiom of self-expression, not dilute it. In the next 50 years, as the average human life-span increases dramatically, the likelihood is that more and more artists will experiment beyond their elected discipline. They'll be bored to death if they don't.

If those who wave the One Thing Only rulebook fail to see this, it's because they're snooty and protectionist. There's also an intellectual laziness about them, as if the effort of re-categorising someone weren't worth making: John Updike and Margaret Atwood may take themselves seriously as poets, but since they're already labelled as novelists, why should we? Stephen Fry and Ben Elton are comedians: no need to bother with their novels, then - they're obviously only dabbling.

Underneath all this lies the myth of the Master and the masterwork, which the monocrats elaborate as follows. At a young age the Artist discovers his (yes, it's a he) true vocation. A long apprenticeship follows, and struggles with poverty, hunger, patrons, drink, drugs, madness, beautiful women and false artistic directions. But at last, in a flurry of creativity born of discipline and genius, the Artist achieves a masterpiece, or series of masterpieces, the One True Thing, alongside which the rest of his work is doodling juvenilia or stale repetition.

It's a seductive myth: according to the monophiles, only if artists brood under the one stormcloud all their days will lightning strike. But there are many past masters whose case it doesn't fit: those, like Picasso, who renew themselves time and again through fresh forms and methods; those like the Russian artist Alexander Rodchenko, forced by the state to abandon one road (Cubism) and take another he equally excelled at (photography); those like Anita Brookner and Mary Wesley who found their metier (fiction) late on in life; those like William Blake whom we want to call both poet and painter.

It's also a myth that sits very oddly with how most of us at the end of this century think and live. We move around, no longer rooted in the One Place. We change partners, discovering more than One True Love. We have short-term contracts, not expecting or even wanting a Job for Life. In education, the trend is towards pick and mix modules, not specialism. In the increasingly feminised workplace, the demand is for plurality, flexibility, multiplicity - attributes lacking in old-style Western leaders or captains of industry (the kind who couldn't walk and chew gum at the same time). A Jack of all trades is a master of none, but a Jill juggling jobs and babies is a role-model for our age. People Who Do Different Things used to be called dilettantes (bad); now they're called pluralists (good).

Contemporary art can't help but be influenced by this anti-compartmentalist zeitgeist. Perhaps that's what's meant by talk of the renaissance in British culture - that Leonardo da Vinci, whose career embraced painting, music, architecture, city planning, anatomy, geometry, aviation, hydrology and the military arts, would have understood us.

"I tried each thing, only some were immortal and free," begins a poem by John Ashbery. As this suggests, not everything we try will work out. But what a fatal lack of curiosity not to have a go, to choose our groove at 20 and never leave it. Paul McCartney did his thing with the Beatles, with Linda and Wings, and on his own. It's probably the thing he does best. But if he wants to do something else, why not?