For Monet's attachment to pleasure is a driving force of his art, a virtue and a principle. He was one of the first modern artists to declare an unabashed delight in pigment. There is something almost heroic in his love of paint. Certainly he shared this aesthetic hedonism with impressionist comrades, especially Manet and Renoir. But Manet's feeling for pleasure is that of a fastidious aristocrat of the brush, and Renoir's sensuality is tactile. Monet never painted a nude, and such a thing is not quite imaginable. His own sensuality was purely optical, so much so that it tended to dissolve in light and water. Monet seems not to have liked objects very much, and still-life was another genre he avoided.
By happy chance the NG's exhibition is able to cover Monet's career without going beyond London for loans. First the NG has its own holdings. Then the gallery has borrowed Monets from the Tate. The Courtauld Institute has lent three pictures. Finally there are seven canvases from private collections. They are pictures of great rarity and interest, often filling in gaps in the public collections. So, all in all, these two dozen paintings span Monet's career over six decades, from his beginnings in his native Le Havre in the 1860s to the final visions of the Water Lilies painted at his home in Giverny in the years before his death in 1926.
This is therefore a retrospective in miniature. We have a fine impression of the continuity and high quality of Monet's work. He was an even painter, like Corot or Claude. Monet's oeuvre as a whole is extremely large, yet with few failed paintings. On occasion he produced some strange ones, particularly towards the end of his career, but he didn't trip up - as, for instance, Manet sometimes did. Perhaps that was because Monet was not a revolutionary by temperament, or because he realised that his nature and destiny was to be a landscapist. In any case, the sheer flow of consummately realised work was a lifetime's achievement, and we can sense this triumph from the relatively small number of paintings in the exhibition.
Blessed from the beginning with an amazing facility, Monet might have become a marine artist, or a painter of the clothed figure, or the contemporary scene, and of course there are early paintings of this sort. One of them is The Beach at Trouville (there's sand in its paint), which shows his young wife with a parasol and must have been painted very rapidly. This is so familiar that I am more intrigued by a still-life of apples, pears and grapes, which comes from a private collection. Reasonably enough, the NG dates it "around 1867". I was initially startled by this unknown picture. Were it not in the present exhibition, how many people would recognise it as from Monet's hand? It was his response to Courbet, but not done humbly. Note how the painting comes forward to the spectator. In later life Monet's spirit resides in the distance,as though there were a particular extension of space between his subject and his easel.
During the wonderful summer of 1869, Monet painted side by side with Renoir at La Grenouillere, a bathing spot on the Seine. Bathers at La Grenouillere was lost for many years and entered the NG's collection only in 1979. Here's a particularly vivid example of the early impressionist faith in open-air, spontaneous painting. It could not have been done, and neither could Renoir's contemporary pictures, without innate artistic gifts in the wrist and fingers. All the masters of Impressionism were virtuosos of handling, each of them in individual ways; and for each of them such virtuosity began relatively early in life. In this picture the confidence of the smears, dabs, unequal strokes, bits of broken colour and so on were unprecedented. Unrevolutionary, Monet had created a new style for himself, almost from innocence.
However, he realised that it should not be a rule to paint before nature. Monet's most beautiful paintings were often those which were most touched up after an expedition to look at the outside world. He was a studio artist. That is, he knew how to "cook" his canvases. He seldom overcooked them because he had such a delicate and committed sense of beauty. Nature has many good points, but modern beauty is mainly found in the house. A further advantage of being a studio artist is that it's easier to meditate indoors than outdoors: so the studio atmosphere helped Monet to invent a progressive kind of landscape picture.
For instance, he often divided his canvases in half by placing poplars or other trees above water, with their reflections on the depicted water. Such paintings (not that it greatly matters) were the first in modern art which would not lose too much of their aesthetic character if hung upside down. What does matter is the sort of forward but vague shimmer Monet gave to his horizons. In classical landscape, the horizon is at the furthest point from the artist or spectator. Monet loved the feeling of distance, but brought expanses beneath the direct and tender motions of his brush.
Hence the nature of his Water Lilies and their relationship to flower painting, which is the most landscape-like form of still-life. At the NG is a more or less conventional picture of flowering mallows in a vase. Now think of a modern art-school exercise. If you have a student who wants to paint cheerfulness and tulips stuck in a milk bottle, make him (or, more often, her) strew the petals over water in a bowl below the easel, and then see what comes out. Colours float and dissolve. This is the sort of thing that Monet discovered in his Giverny garden and studio. I wrote "her" just now with the notion in mind that Monet is a particularly sexless painter, whatever his personal life and habits. His eye loved what he saw and what his fingers did, but that eye had no gender.
National Gallery, WC2 (0171 839 3321), to 5 May.