And they all live in little boxes

EXHIBITIONS; Marcel Duchamp's 'Boxes' contain replicas of earlier works. He called them 'museums' - but were they really an admission of failure? Plus, 'New Displays' at the Tate Gallery

Marcel Duchamp isn't much talked about these days - his reputation as a father of contemporary art has been deeded to Joseph Beuys - and he's not much exhibited either, so the sophisticated show at the Entwistle Gallery has the air of a rarefied investigation. Apart from the once notorious Fountain of 1917, which is the urinal Duchamp sent to an open exhibition, the works on display need to be looked at with the eye of a meticulous, and preferably obsessed, art historian. They are examples of the seven series of "Boxes" that Duchamp produced between 1941 and his death in 1968. They are the size of large attache cases and are portable retrospectives, for each box contains miniature replicas of his work since around 1912.

As usual with Duchamp, the spectator has contradictory feelings. Nothing quite rings true as art, but at the same time we are presented with much artistry. A first impression is that the boxes are the work of a careful craftsman; then one suspects that the actual manufacture was done by someone else. When one considers the purport of Duchamp's various projects it is hard to decide whether he was an intellectual or a charlatan. Certainly he was concerned to trick us as well as to shock. Dishonesty no less than a talent for scandal was part of his equipment. And yet Duchamp could be quite open about his dissimulations. The boxes have a modest appearance; on the other hand their very existence is proof of grand narcissism. I think they show the self-love one often finds in people who make a profession of cynicism. I know, however, that there are people who genuinely believe that Duchamp was a benign and liberating spirit.

Such paradoxes could be multiplied, and are not easy to resolve. In the end people respond to Duchamp according to their attitudes to modern art as a whole. Generally he has been liked by vanguardists and conceptualists. Those who have a strong commitment to painting and sculpture distrust him. I am of the latter party. And it must seem obvious to everyone that if you appreciate, say, Matisse, then Duchamp's offerings cannot satisfy a relish for fine art. It's best to regard him as an embittered casualty of modernism rather than as a master, and this is the interpretation that makes sense of the boxes. Duchamp called them "museums", but that was misleading. In truth they are autobiographical ruminations over failure.

Duchamp's career as a Duchampian began when he realised that his early painting was not up to the mark. His Nude Descending a Staircase, the King and Queen Surrounded by Swift Nudes and the Chocolate Grinder, all done at the beginning of the First World War, could not compete with the Cubism and Futurism from which they derived. Tu m' of 1918, his last painting and made in his New York exile, is much better and might have led somewhere. But by this time Duchamp was a Dadaist making a career out of anti-art and was absorbed in his most famous work, The Bride Stripped Bare by her Bachelors, Even, completed in 1923. It's a clever parody of painting. Instead of canvas, glass. Colour is inexpressive. All drawing is mechanical rather than freehand and the motifs, once deciphered, turn out to be a symphony of negativism.

Little wonder that Duchamp's resentments were best contained in boxes. Within artefacts he could indulge himself without setting his art against anyone else's. He could be rid of the demanding and competitive environment of a mixed exhibition. I call Duchamp a "Duchampian" because he made a fetish of his personality. At the Entwistle Gallery they understand this very well. The work is admirably curated and installed, generally within vitrines, there are photographs and much talk of his prowess at chess. Best to wise up on the literature before going to examine the tiny objects.

AT THE Tate Gallery, the latest set of "New Displays" is a homage to the financial power of the new German collecting. Josef Froelich is a Stuttgart industrialist who became interested in art after meeting Joseph Beuys in 1982. He has since spent millions on German and American artists, all of whom will be shown in due course at Millbank and (it is hinted) may become part of the Tate's permanent collection at Bankside. Not all are on view at the moment. From the catalogue the collection looks dreadful, but maybe it will turn out to have historical value.

The more dramatic Froelich possessions are in the Tate's central Duveen galleries. Carl Andre has the space nearest the front door. Then there is pseudo-furniture sculpture by Richard Artschwager and finally a generous number of pieces by Bruce Nauman. His violent videos are meant to disturb. So they do, for a time, and they are the most effective of Nauman's contributions. As many people have discovered before him, you can't make sculpture more exciting by hanging it from the ceiling. Nor does Nauman succeed with neon light tubes. What can you do with neon? Not much. Nauman's predecessor Dan Flavin (to be featured in the next "New Displays") used light tubes in relation to recent American abstract painting, in particular Barnett Newman's. It looks as though Nauman has taken his cue from advertising - such a lively visual industry, though it does no good to truth or to art.

! Duchamp: Entwistle Gallery, W1 (0171 734 6440), to 27 Jun. 'New Displays': Tate Gallery, SW1 (0171 887 8000), to 8 Sept.