The artist known as Prince

"He takes photographs but he's not considered a photographer," said one critic. "He paints but somehow he is not a painter." This unresolved argument rumbles on and on, in much the same way as it always has, for the American artist Richard Prince has defied every classification for nearly a quarter of a century.

Sometimes his output defies you to like it, for it can be lifeless, banal and inaccessible. But as the same critic put it, his work can creep up on you "when you're not looking, and quietly detonate with a delayed fuse". Prince is no stranger to hyperbole. So if he's neither "painter" nor "photographer" but adroit at each discipline, what exactly is he?

"Uh ... I guess that means I am an artist," he explains. It means, in fact, that he is many things. Prince has been variously and simultaneously a photo-collagist, a conceptual photographer, a painter, a perceptive commentator on anything and everything from bibliomania to the lure of the old Times Square porn theatres, and a prose writer of exceptional talents.

He has painted in enamel on the fibreglass car hoods that you send off for from hot-rod magazines - "I wanted to paint something already painted," he explains - so he's a sculptor of sorts, too.

But if you have heard of him at all over here, it will probably be as an influence on others for kickstarting the "appropriation movement", which is about creeping up and thieving ideas. He re-photographs or re-represents in crayon, paint or printer's ink items he finds in magazines - the cowboys from the Marlboro advertisements comprised an early body of work. As for his effect on some of our own Young British Artists, if you look closely at Peter Davies's obsessional Text Painting (1996), which showed as part of Sensation! at the Royal Academy, halfway down his litany of favourite artists you will find: "Richard Prince, now this really is the greatest thing if ever there was bare-faced cheek ... "

His influence can also be felt in some of Gary Hume's work, while artist Angus Fairhurst, partner of Sarah Lucas, has written a thesis on him. But Prince has had only two solo shows here, in London and Edinburgh.

In the US, he is lionised. His biography for his forthcoming London exhibition, where a show of his joke paintings, "white" paintings and photographic works opens soon, lists half-a-dozen pages of exhibitions, solo and group shows, publications and assorted citations elsewhere. In 1992 he was given a retrospective at the Whitney Museum of American Art in New York. The influential Swiss art magazine Parkett devoted a slab-sized issue to his work, with essays by Edmund White and the late Kathy Acker. He was included in Fashion, an anthology of contemporary fashion photography, which is odd, for he has never taken a fashion picture in his life. Well, not one of his own, at least.

He began appropriating images back in the mid-1970s, when he found himself at the publishing house Time-Life, clipping editorial material from newspapers and magazines for staff writers. The leftover pictures became his available material: cigarette and watch advertisements, fashion pictures and beauty campaigns. "I was alone," he has said of this time, "for eight to 12 hours a day tearing up magazines. Page by page." In 1977 he took four images, pictures of different living rooms culled from the proto-lifestyle section of the New York Times Magazine, and re-photographed them.

If his brilliant art is difficult to pigeonhole, he resists formal biographical categorisation, too. For the catalogue to his exhibition, Spiritual America, he invented an interview with himself conducted by author JG Ballard in 1967. Some of it may be true, but it's hard to know precisely what. Probably only that he was born in the Panama Canal Zone in 1949.

A large part of the "interview" is taken up with a dialogue between the two men about British Airways, which is supposedly flying Ballard back and forth from Kingston to London, unable to determine his status or nationality. Which is telling, this contemplation on identity, for Prince's oeuvre depends for much of its resonance on the disputation of authorship. He has called his torn-out ephemera "the authorless pages". Prince seems to like to keep a low profile - or at least a disguised one - though he was compliant enough about the photographs accompanying this piece. There is a small portrait of him in his Whitney catalogue (the smallest image in the book) taken by Larry Clark (Kids), an enthusiastic appropriator, too. Prince has completed self-portraits over the years, but they tend to be imaginary representations. For one, a collaboration with fellow artist Cindy Sherman, both wore red wigs and presented each as the other. He has also appeared in a suit and tie wearing eyeliner and lipstick.

In the mid-Eighties, Prince began to re-draw cartoons in pencil, mimicking his re-photography of found images. Then he began to draw just the punchlines which, it has been pointed out, were often supplied by a hand other than the original cartoonist. Often the cartoons and jokes take sexual mores as their starting point - infidelity and duplicity - and racial confrontations, too. By isolating the straplines he manages to isolate a middle-American streak of perversity and dysfunctionalism.

Later, he would compound two separate and unconnected cartoons one over the other, or layer them further with writing or disconnected text. He might deconstruct them, and he mixed punchlines and images to produce odd elliptical worlds, full of Freudian slips. Against a photograph of clouds runs the following caption: "I went to see a psychiatrist. He said, `Tell me everything.' I did, and now he's doing my act." The perfect epigram for a 25-year career of stealing other people's acts.

In the end he is, as he says, an artist, endlessly inventive and increasingly significant. He told Larry Clark that photography was dead and he killed it. "All the pictures were already taken," he explains. "There wasn't any need to take any more. I still agree with it in a theoretical way - but I'm not very theoretical. As an idea it's true, but I don't have any ideas"

`Richard Prince', 7 April to 22 May, at Sadie Coles HQ, 35 Heddon Street, London W1 (0171-434 2227)