I ONCE FOUND myself suggesting to a writer that maybe his writing was two-dimensional. He looked at me with a wild hope: You really think it has that many dimensions? His was a first-person narrative, transparently autobiographical. He wanted to tell the world about his travels, his reasons for travelling, the women he made love to on his travels, and how his travels had brought him to a better understanding of himself. Reading that text was like being in a room with graffiti covering every available space. Someone called Jamie had been within these four walls for a long time: JAMIE WAS HERE! JAMIE'S STILL HERE! JAMIE'S FLYING! THE HOSTESS HAS THE HOTS FOR JAMIE! NOW JAMIE'S FEELING SAD IN AUCKLAND!

The book was about travel, but the narrator was never able to move out of himself: he carried the cage of self spectacularly and ludicrously around the world with him. In some first-person narratives, that first person is the only person. I call this the problem of the trapped narrator. The trapped narrator often has a lot of energy. The trapped narrator will dance for you, sing, bang the cymbals, do somersaults, mime his entire life, with particularly vigorous gestures for sexual adventures. But, after a while, all the reader sees are the bars of the cage.

Writing in the first person does not automatically create a voice and a character. A first-person character — even, or should I say especially, an autobiographical character — has to be created. It's a massive error of technique for a writer to assume that all that is necessary is simply to be that first-person character, or that writing this character will be like letting water run downhill.

Jean Rhys has given us several self-absorbed female narrators who are undoubtedly autobiographical. But she doesn't make the mistake, as a writer, of becoming absorbed in her narrator's self-absorption: she creates the self-absorbed character out of knowledge and pitilessly clear vision, and she keeps her attention not on indulging her narrator's emotions but on placing the character subtly in the perspectives of a shifting world. Rhys may write about trapped women, but, in her novels and stories, you will never witness the spectacle of the trapped narrator. She knew that the task of fiction is not to tell the world how miserable you are and how that misery is everybody else's fault. She would never have confused the task of exciting with the much lazier process of becoming excited.

The first person gives the writer the most seductive of opportunities: to create a mesmerising, haunting voice; to be the Ancient Mariner. Wedding guests will abandon their weddings to listen and wonder. But this opportunity brings with it several potentially fatal traps. It's so very easy to be not the Ancient Mariner but the club bore, what the Buddhists call a 'hungry ghost', tugging at the sleeves of wedding guests because surely one at least must be deeply hungry for the stories of Jamie being abandoned in the snow on Mount Cook, Jamie making love on Waikiki Beach, Jamie in a moment of marvellous insight wondering whether he would have been better off staying at home. All I did was shoot an albatross, says Jamie, and look what happened to me.

Writing in the first person requires a highly developed technique. The difference between Jean and Jamie is not to be found in the quality of their personal characters or experiences but in the extent of their understanding of technique. Jamie is like the guitarist who has learned three chords: what more does a guitarist need because everyone knows that the only purpose of the guitar is to accompany the voice, and Jamie's absolutely sure that his is a voice that will command attention, maybe even without that pesky guitar.

Jean Rhys, on the other hand, fully understood the subtle meanings that can be created through the relationship of the voice and the guitar. Where Jamie plonks his three chords endlessly around the world, Jean sits in a Bloomsbury bedsit and discovers not only the hundreds of possible chords but also the infinite possibilities of relationships between chords, and the implications of these relationships for the graceful and meaningful carriage of the first-person voice.

Jamie, for all his crashing cymbals and enthusiastic miming, has not yet learned the art of modulation. And, without mastery of that art, a writer — almost inevitably — is a trapped narrator.

Modulation takes writing from two dimensions to three, and releases the first-person writer from the cage of self. How is it done? asks Jamie. And I start — the first shy lesson at the piano — by showing him the movements of the voice in the first two pages of Till September Petronella.

But we all know Jamie: he will simply not have the patience to learn a long and subtle art. His writing has two dimensions already — can't I just slip him a quick way to add a third?