Not only is his work controversial because it is essentially graffiti, but because his stencilled works of "?art' often fetch thousands at auction.

So is Banksy, one of the world's best known artists, a spray-can wielding charlatan or an urban, post-modern prophet?

Despite the fact that his works are so popular he remains a recluse and an unknown person; almost no details about his life, including his name, are publically known.

In recent years the self-described "art-terrorist' has used his art for overtly political purposes; in 2005 he painted nine images on the Israeli West Bank wall including a child digging a hole through the structure, in 2001 he travelled to Mexico to paint murals for the Zapatista Army of National Liberation and, in Bristol Zoo, he once painted the words 'I want out. This place is too cold. Keeper smells. Boring, boring, boring' in the elephant enclosure.

He remains best known in the UK for his stencil-graffiti and for creating "subverted' paintings; adaptations of famous masterpieces that are either redrawn or added to with satirical slogans.

The question has often been posed; is Banksy, whose stencil of a green Mona Lisa with paint dripping from her eyes sold for £57,600 at a Sotheby's auction, an overpaid prankster or one of the world's finest living artists?

Some say he is the most exciting artist to come out of the UK for many years, others say he is simply a vandal. Whatever your opinion there is no escaping the enticing contradictions inherent in the life and work of the man they call "Banksy': he is fervently" anti-establishment' and yet he, and his work which regularly fetches tens of thousands of pounds at auction, are constantly in the public-eye. He is even reported to have signed a sponsorship deal with Puma. In 2006, his first U.S. exhibition was an awfully glamorous affair which sought great publicity, operated valet parking and was attended by numerous Hollywood megastars including Jude Law. Numbered prints were on sale for $500 at the exhibition which seemingly flew in the face of all that Banksy stands for. "Yes, there probably is some contradiction," Banksy's spokesman Simon Munnery said, "It depends on what he does with the money, right? Maybe he makes more art. Maybe he's getting more ambitious."

Regardless of the media hype surrounding Banksy and the fact that his supporters say he never asked for such attention "" his "I can't believe you morons actually buy this shit' painting sold for £3,000 on eBay his work raises important questions about the true nature of art. Most critics agree that art is not simply about communication per se but about substance; about that which is being communicated and how universally it is understood. Since the rise of postmodernism this ideal has been propagated in as many stimulating ways as it has dull ones but Banksy himself can never be accused of making art for art's sake. He speaks to the public in its own voice and, whatever your opinion about the depth and grandeur of his work (or lack thereof) there's no denying that his message resonates with the general public and in so doing, places Banksy at the helm of modern art. For many, Banksy carries a torch passed from Warhol to Pollock and, in the words of Dubuffet, creates something which is so painfully lacking in today's world: "raw art.'

The images have to be appreciated as they are intended; on the street, otherwise a hugely important aspect of the work, namely, the context, gets overlooked. However, although public and strikingly original, there are many who say that Banksy merely creates "background' art and therefore never elevates his work beyond that of a "prankster with a spray can'. There is no comparison possible with for example the work of Damien Hurst. Perhaps if Banksy focused on producing some well thought out canvases, his creations could be as impressive and timeless as those of his predecessors. It is unlikely however, that we will ever discover whether Banksy won't, or simply can't, take such a step.

The Guardian's Jonathan Jones: "Essentially, he is someone talking any rubbish that comes into his head, for the sake of it. And what comes into his head is a stew of received ideas - nothing really likely to challenge anyone. The easy humour that makes his work superficially likable removes from it any hope of being mad or poetic."

He is essentially a comic artist, the humour of his designs outweighs their political vigour. But, regardless of what you think about the depth and validity of his messages, there is no denying that he is quite simply a talented painter and stenciler and most would add also a very humorous and capable spokesman for modern society.

He has also written a book, Wall and Pieces, which has been hailed as being "perfectly calculated to divert the leftist on the loo " self-proclaimed enemies of the state, fermenting in their own self-righteousness."

But perhaps the time for such debates as this one has past and that one of the very things that Banksy's work shows us is that to get too serious and too stuffy about Art is to miss the point and to miss great opportunities. So rather than trying to fit Banksy into a genre or push him onto a pedestal we should be pushing the boundaries of our appreciation for "art' and questioning our habitual need for categorization.