ART / Getting hold of the wrong Impression: 'The Origins of Impressionism', on show at the Grand Palais in Paris, throws a spanner in the works. Andrew Graham-Dixon reports

Mockingly derived from the title of Monet's painting, Impression, Soleil Levant, the term 'Impressionism' was originally intended as an insult. An art founded on 'impressions' of the world? Impressionism? What an absurd notion. It will never catch on. The rest, as they say, is history.

But the history of the movement itself is no simple matter, if the organisers of 'The Origins of Impressionism', at the Grand Palais in Paris, are to be believed. The exhibition is a challenge laid down to the falsifying terminology of art history. Its main thesis (something of a paradox in the light of its title) appears to be that Impressionism, in fact, never really existed - or that, if it did, it was misnamed.

The tracing of origins is a favourite occupation of art historians, but it is also one which proves, more often than not, fruitless. It is possible to argue that the first Impressionist was really an Englishman, John Constable. A case can be made for Turner, too, but why stop there? Why not make Rembrandt, or Velazquez, or Titian, the ur-Impressionist? 1859 is the (inevitably) arbitrary date which the organisers of the Grand Palais exhibition have settled on. It will have to do.

The show begins with a broad selection of works exhibited at the 1859 Paris Salon: a pot-pourri of the sort of art the founding fathers of Impressionism would revolt against. Bouguereau's Le Jour des Morts - a pair of theatrically grieving young ladies lay wreaths on a grave - is a lachrymose exercise in mid-19th-century sentimental genre painting of just the kind that it was de rigeur, in Impressionist circles, to despise. Jean- Leon Gerome's Le Roi Candaule would also have been anathema: a feeble piece of soft-porn disguised as high art, a mythological painting of a woman undressing in obscure Neoclassical circumstances. Manet (and, after him, Degas) would call a spade a spade. When they wanted to paint naked women, they painted real naked women. Gerome's coquettish stripper in Grecian fancy dress is put to shame by Manet's Olympia, that hard-faced, hard-nosed businesswoman. You can look, but you can't touch, her expression says, unless you've got ready cash. No credit cards taken.

But the standard view of the Impressionists - as artists who went against the academic grain in the name of truthfulness - rests on an extreme simplification. Most of the major artists of the 1860s and after, in France, would remain haunted by the very artistic traditions which they were in the process of destroying. The show includes narrative or mythological paintings by Manet, by Cezanne and by Degas, which are often overlooked or dismissed as freaks of their respective oeuvres or as misguided juvenilia. Degas's Scene de Guerre de Moyen Age is a peculiar fantasy of mediaeval massacre and affray littered with poleaxed nudes. Cezanne's Pastorale, in which fat and oddly deformed naked bathers like prototype Michelin men disport themselves on a riverbank lit sporadically by flashes as if by nocturnal lightning, is even stranger.

But, although such pictures may not be typical of the styles with which these artists have come to be associated, they demonstrate their uneasy, clinging relationship to the art of the past and shed light on their more famous works. Manet's Olympia would be self-consciously intended, not just as a rebuke to the flaccid academic nudes of Gerome or Cabanel, but as a modern equivalent to Titian's Venus of Urbino. Cezanne's Bathers would be Poussin's Bacchanales in another form. Degas' pictures of racehorses and their jockeys at Saint Cloud or Longchamp would be modern but also intensely classical in spirit: Parthenon friezes re- created in paint. There are no clean breaks with the past in art.

'The Origins of Impressionism' has been organised, with presumably mischievous intent, along 19th-century academic lines. The paintings are displayed by genre rather than artist and placed in categories which include 'The Nude', 'Still Life', 'Landscape', 'Portrait' and 'Marine Painting'. This structure turns out to be almost completely unworkable, because hardly any of the pictures neatly fit the categories assigned to them. The effect seems to be deliberate and is certainly revealing.

Manet's still enigmatic Dejeuner sur l'Herbe is exemplary: neither a narrative painting nor a landscape painting nor a painting of the nude nor quite a fete champtre but, rather, a weird and potent combination of all of those things. Degas' Femme aux Chrysanthemes is likewise, if less stridently, torn between genres - in this case the still life and portrait - and that, indeed, is the point of the picture. A woman's face, placed at the far edge of a composition dominated by a huge floral arrangement, has been tellingly marginalised by the artist, as if in acknowledgement of the fact that visual experience is usually awkward and unstructured in just this disconcerting way. Seeing, Degas quietly observes, produces those unexpected collisions of subject matter which the old academic taxonomy of genres sought to suppress or conceal.

Something new and strange happened in art during the second half of the 19th century, but it was nothing as simple as the advent of a new and so-called 'Impressionist' style of painting: it was a far more deep-rooted and profound change in the nature of human vision and in the conventions of depiction. The old academic genres came to seem inadequate to the themes and concerns of a new generation of artists, and collapsed under the strain. Or they were transformed: Monet, in the 1860s and 1870s, began to make landscape the pretext for visionary fantasies; Cezanne used still life to grapple with the suppressed demons of his emotional life. Every Cezanne breadknife, every apple teetering on the brink of a white linen tablecloth, is a veiled threat.

But the hero of the exhibition is Manet, and appropriately so since he was never really an Impressionist and the subject of this show is not really Impressionism. Manet's great themes are the awful disconnectedness of things and people and the beautiful but shattered world of modernity. One of the last paintings in the exhibition, his Sur la Plage de Boulogne, is an apparently sunny picture of a group of daytrippers. It is also an image of life as Manet sees it: groups of people, isolated on the far shore of existence, aimlessly drifting through their separate existences. It is a painting of a beach, and also an allegory. Manet felt the meaninglessness of life more acutely than any other early modern French painter. After Manet, there would be no more landscapes and still lifes and portraits and narrative pictures. There would only be paintings: Manets, Cezannes; Van Goghs, Picassos. The true subject of this exhibition is not merely the origins of Impressionism, but the origins of modern art.

Runs at the Grand Palais, Paris, until 8 August; then at the Metropolitan Museum, New York, from 19 September to 8 January 1995.

(Photograph omitted)