Is modern art the cutting edge of creativity or ugly, sensation-seeking and aethetically challenged? Donald Kuspit and Norman Rosenthal cross pallet knives in the last in The Times Higher's series of Controversial Thesis debates

It is fairly shocking that a distinguished and well-known critic and professor of contemporary aesthetics can revel in the fact that a warehouse fire has destroyed works of art by many modern British artists. Sic transit gloria mundi .

This is not the first conflagration in history in which such powerful testaments to human civilisation have been lost to flames - both accidental and deliberate. Paintings by Vel zquez were burnt in the Alcazar in Madrid in 1763, and Titian's great altarpiece The Death of St Peter Martyr was consumed by fire in SS Giovanni e Paolo in Venice in 1864.

Doubtless there will be more in the future. Nevertheless, far more shocking than the latest fire is the Schadenfreude displayed by certain members of the art establishment in response to the news.

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There is nothing new about the auto or man-induced destruction of art. In 1962 Gustav Metzger, a student of David Bomberg alongside Frank Auerbach and Leon Kossoff in the 1940s, invented the auto-destructive art movement, whose manifesto he entitled "Auto-destructive art, machine art, auto-creative art". Three years later, Arthur Danto, an American critic as distinguished as Donald Kuspit, had his aesthetic mind changed for him when in an often-described moment he encountered Andy Warhol's Brillo Boxes in an exhibition at the Stable Gallery in New York in 1964. For Danto, subjectively, that show marked the symbolic end of the modern movement that had begun 100 years earlier with Manet and his critic Baudelaire.

Critics like their art to be simply explainable, or rather they seem unable to avoid forcing a construct out of their own inevitable subjectivity. I have nothing against that in principle. Indeed I would argue strongly that subjective judgement is the only thing that is valid in the evaluation of art. When, a few weeks ago, I received an advance copy of Kuspit's new book, The End of Art , I regarded it with a mixture of extreme scepticism and great delight.

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Delight first. The dust jacket is programmatic. On the front, the author has chosen to illustrate a multiple ashtray by Damien Hirst, glazed with a fairly shocking trompe l'oeil representation of cigarette butts and ash. At one level, this is a terrific visual joke and pun (nothing wrong with that), and at another, an object that can be read as an anti-smoking manifesto or as an object in praise of smoking; or as neither. As Duchamp famously said: "The work of art is completed by the viewer." I allowed myself a moment of national pride that a US professor should have chosen a small pi¨¨ce d'occasion by Hirst to adorn the cover of his book.

Now for the scepticism. After some lengthy and often quite specious and arbitrary arguments about the "post-aesthetic", Kuspit dismisses as worthless Pop Art, Fluxus, Minimalism, Arte Povera, much of Neo-Expressionism and the world around artists such as Jeff Koons. He vilifies the art status that has been claimed for merde . But what of Salvador Dali, Piero Manzoni, Joseph Beuys, Robert Mapplethorpe, Kiki Smith, Mike Kelley and Chris Ofili?

At the end of his book the professor cannot help but pull back, rediscovering the Christ-like transcendentalism of Vincent van Gogh, as opposed to the corrupting dandyism of Edouard Manet. He identifies a new category of painters, the "new old masters", who represent the "principle of hope". A work by one of their number, Don Eddy, is illustrated on the back of the dust jacket. Such hyper-realist painting adds little to the sum of human culture that, despite Kuspit's ideas, can define itself only by looking, describing where no man or woman has been or looked before, using any available means. Oil on canvas is one way, but any medium is valid.

I welcome the vast increase in audiences for the visual arts. And it is only in the past decade or so that the art world has finally lost its European-American focus. The market is a fact of art and culture, and it always has been. Each work of art, each exhibition has to be enjoyed (or not enjoyed) for itself and on its own terms; to paraphrase Ernst Gombrich:

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"All art is illusion", and with it, as in theatre, in literature and in music, comes some kind of catharsis that ultimately becomes a part of personal and, with luck, social and historical memory. I am happy for Kuspit to defend David Bierk, Vincent Desiderio and others whose work he illustrates but which does not interest me, but I cannot accept his category of "new old masters". He must allow us to establish our own hierarchy of art, and must equally accept that artists such as Damien Hirst, the Chapman brothers and Tracey Emin can neither be dismissed nor written out of history. They have done too much that is new and revelatory, each in their own terms, for that. They are not yet ready to be embalmed.

Norman Rosenthal is exhibitions secretary of the Royal Academy of Arts.