"Instinct is 10 times stronger than knowledge," the painter once said, and he spent his life trying - with some success - to make his pictures look more passionate than thoughtful. The Whitechapel Art Gallery's current exhibition of Nolde's art is the first showing, in this country, of a broad spectrum of his painting, and it turns out to be a sporadically impressive demonstration of his unevenness. There is a very fine line dividing Nolde the father of German Expressionism from Nolde the pavement artist, and it is frequently crossed. But while the barbarism that he so assiduously cultivated in himself was too often forced, at least he never descended to the stale, repetitive formulae of his greatly overrated contemporary and co-Expressionist, Edvard Munch. Nolde's most redeeming characteristic was his perpetual readiness to take risks, to fall flat on his face time and time again in the hope that, just occasionally, he might pull off a good picture.
At his sloppiest and most calculatingly "primitive", for example in the pictures he painted of African masks n Berlin's ethnographic museum in 1911, Nolde can be quite spectacularly dreadful - as bad as, say, John Bratby at his worst, which is really very bad indeed. Yet at his best, particularly in his rich, dark, heavily melancholic watercolours of northern seas and northern landscapes at dusk, he seems an almost brilliant artist. Much of Nolde's work is plainly derivative, but honestly so, and many of his watercolours and oils were painted in a spirit of modest tribute to Turner. What makes them Nolde's own is his determined, wilful application of a Fauve palette to Turnerian subject matter, and out of the collision of those two borrowings he formed his style as a painter of landscape.
Nolde's Tug-Boat on the Elbe is an Expressionist homage to Turner's Staffa, Fingal's Cave, an almost literal copy in fact, transformed only in the colour and the handling. Turner's delicate atmosphere of haze and fog, his trail of steam across the sea, as insubstantial as a shadow, has become Nolde's sea and sky of gestural marks painted in bright yellow paint churned up like butter. The effect is impressive if perverse, but almost all painters find themselves by imitating others (Turner partly came to be Turner by imitating Claude and finding out his differences from him). By the time Nolde painted the small, undated watercolour Evening Landscape (North Friesland), he had come to a happier accommodation with the ghosts of the past. This is the most beautiful picture in the whole show, and its dense, saturated reds, maroons and blacks, arranged in subtle stripes and bands and sfumato puffs, almost like exhalations of pure colour, begin perhaps to predict the Abstract Expressionist canvases of Mark Rothko.
Large spiritual claims have been made for Nolde's colourful empty spaces, and he was clearly, for much of his life, an artist in search of God, or at least of some kind of higher truth. He took spiritual refuge, or tried to do so, for a good deal of the time, in a form of late Romantic pantheism of which his colour-soaked landscape watercolours are by far the most powerful expression. His pictures of flowers, claimed by many art historians to be among the finest and most numinous works of the early 20th century, are not very impressive at all on this showing. Nolde may have attempted to find heaven in a wild flower, but his bouquets of dahlias and sunflowers are terribly tame and second-hand: self-consciously primitive reworkings of themes from Odilon Redon and Van Gogh, done once more without feeling.
Nolde's constant desire to root his art in "feelings that are ancient and eternal" is the constant running through the diversity of his often bewilderingly various oeuvre. He painted many pictures of myth and fairy- tale inhabited by energetically crude, lumpen men and women giving vent to what Nolde fancied were the primal impulses of the German Volkisch spirit: there is much drinking and cackling and gleeful showing of breasts in his art. Candle Dancers is the exuberant masterpiece of this particular genre of Nolde's paintings, a picture of cavorting topless girls in stripy dresses on a red ground. Nolde's Dionysian fantasies are his nods to the classical tradition in European painting, among other things. They look like Poussin bacchanalians viciously beaten up in a fight.
Odd though it now seems, the style of such paintings was briefly considered as a potential for Nazi propaganda, and when Goebbels came to power with Hitler and the National Socialist Party he hung his office with Noldes and announced that "Today we are all Expressionists". The flirtation did not last long. The National Socialists reverted to staid and demure Aryan classicism and Nolde was branded "degenerate". He spent his later years in fear of the Gestapo, forbidden to paint but continuing, despite Nazi injunctions, to produce watercolours which he hid under the floorboards of his house in rural Seebull. In one of them, we see a naked young woman with hair as flaming red as any of his sunsets embracing an old man who looks like Nolde himself: degenerate and proud of it.
n At the Whitechapel Art Gallery, London E1 (0171-377 0107) to 25 Feb