ART / Manet can't buy you love: Samuel Courtauld amassed one of the great collections of Impressionist and Post-Impressionist painting. So why are we reluctant to go and see it?

FAMILIAR though they are, the Impressionist paintings that belong to the Courtauld Institute of Art never fail to thrill. The Courtauld owns one of the greatest paintings of the late Western tradition, Manet's A Bar at the Folies-Bergere, and here also are wonderful works by Cezanne, Degas, Gauguin, Van Gogh, Monet and Renoir, each of whom is represented at or very near the height of his achievement.

John Murdoch, the new director of the Institute's gallery, somewhat ruefully points out that his paintings are better than the pictures from the Barnes Foundation that caused such a stir when exhibited in Paris last year. Rueful because so few people come to see the paintings. Attendance at the gallery (which also contains important Renaissance and Baroque art) has recently fallen to as few as 300 visitors a day, way below the break-even point. So 'The Great Impressionists' is an attempt to publicise the Courtauld holdings.

The collection moved to the historic premises of William Chambers's Somerset House four years ago. Built in 1777, it is a fine example of Palladian architecture. But most art-world professionals, and no doubt visitors too, were dismayed by the insensitive installation of the pictures. In particular, the modern screens in Chambers's Great Room were offensive. Murdoch's rearrangement has allowed this beautiful space to return to its original dignity. It may not be absolutely ideal for hanging modern art but the Courtauld pictures are so good that they overcome any minor inconveniences in their surroundings.

Samuel Courtauld began to buy Impressionist paintings in 1922. He amassed a private collection and also established a fund for the purchase of paintings by the National and Tate Galleries. Most of the private collection was given to the institute that bears his name, but some paintings were given or bequeathed to friends and family. The present display reunites many of these works, so we now see Manet's The Road-Pavers, Rue Mosnier and Renoir's charming landscape Spring side by side with the paintings by the same artists that we know so well. Courtauld's collecting has never been examined so thoroughly, and this is a fitting tribute to his munificence and public spirit.

Courtauld's activities as patron and collector are described by John House, Andrew Stephenson and others in the catalogue of the exhibition, Impressionism for England (Yale University Press, pounds 14.95). Stephenson's essay is particularly interesting. He links Courtauld to the Bloomsbury group and Roger Fry, notes the idea of the 'layman aesthete' and points out that in these circles, enlightened by British standards, there was little enthusiasm for the Cubism of Picasso and Braque. In general, then, the Courtauld collection scarcely touches the 20th century.

What we see is the shift between Impressionism and Post-Impressionism: the generation of Monet and Manet, first prominent in the 1860s, accompanied always by the withdrawn Cezanne, succeeded by artists like Gauguin and Van Gogh, whose paintings in the Courtauld belong to around 1880. There's a Picasso of 1901, the Child with a Pigeon, and a convincing Modigliani nude of 1906, but really this is a show about late- 19th-century painting - and painting only, for Courtauld was evidently unmoved by sculpture.

One concludes that Manet and Cezanne are supreme. I find Manet to be the finer of these, admittedly incomparable, artists. His A Bar at the Folies-Bergere dominates Chambers's Great Room. Few paintings have been more admired and discussed. The 'new art history', properly enough, has concentrated on Manet's understanding of Parisian social life and its tensions. Feminists speak of the 'availability' and simultaneous dignity of the barmaid. And yet these valuable readings can only be partial; I for one always find some new pleasure in the picture.

A lick of the brush here, a touch or stab of colour there, masterly negligence throughout that proves on reflection not to be negligent at all, rhymes and repetitions in quite different parts of the canvas; all these aspects slow the eye. It is as though Manet wants us to have a temporal rather than immediate experience. Detail in the painting comes in flow rather than in part, and this is one reason why we feel the canvas to be symphonic. It was Manet's last major painting, a youthful adieu to his art, yet with the summarising, untroubled vision of sublime artists who died at a greater age. It echoes the spirit of the later Titian.

This is not surprising, given Manet's admiration for the Venetian. He spoke most often of Titian's light, but the old master's motifs are also in Manet's art. Perhaps fancifully, I dream of his barmaid as one of those Titian (or Tintoretto) goddesses who rise from the ocean. She is the modern Venus Anadyomene. Though Manet was not specifically a marine artist, the way he painted the sea contributed to the inexact distances and liquid variability of such an interior as this. We might almost read the painting as a landscape, so far does Manet cast his eye.

He still further elides the distinctions between the conventional genres of painting. Within this oceanic interior the portrait may be paramount, yet is finally not so important as the still life, which extends from one side of the canvas to the other. Most still lifes are concentrated on a table and come in a squarish picture. But these bottles, the glass, flowers, fruit and vase, are in a landscape- shaped canvas and are seen in a line, with a daring gap in the centre of the extended marble bar, itself like a beach or a sea shelf.

Beyond all this suggestion is the endless virtuosity with mirrors. Manet as virtuoso is utterly pictorial. It is not coincidental that A Bar at the Folies-Bergere is less like a photograph than any other descriptive painting one can imagine. Manet lived in the modern world and relished its ways, but at bottom he was an aesthete who cared for pigment alone. This love of pigment is also, I guess, characteristic of Courtauld's eye. In his place I would have bought not only sculpture but hundreds of drawings: in the 1920s you could get masterpieces on paper for a few guineas. But he didn't. The living palpability of paint (so unlike the fabrics from which he made his fortune) was what he needed.

French painting served this appetite well. In the last four decades of the century its handling was more varied and expressive than at any time before or since. Impressionism gave touch and brushwork unprecedented eloquence. Courtauld's taste responded to this facture. When Monet's brush mingled sky and land, Renoir's caressed his models, Cezanne built his massive passages or Seurat pointedly dabbed, then Courtauld was happy. More of us could be happy too, just by visiting the gallery that houses his purchases. How can people be negligent of such treasures?

'The Great Impressionists at the Courtauld': Somerset House, WC2, 071-873 2526, to 25 Sept.