In Britain, Mark Rothko’s standing as one of the greats of abstract art rests largely on the “chapel” of nine large, sombre abstractions he donated to the Tate Gallery shortly before his suicide in 1970. It was, unusually for anything involving abstract painting, a news story.

Before the paintings were installed, following precisely his stipulation that they must always be shown complete, in a room of their own where visitors could meditate in the quiet environment they provided, the donor had killed himself. Many who would otherwise have run a mile from a roomful of entirely non-representational art went along to sample the experience. If they went to scoff they remained, quite possibly, to pray.

Consequently, many people have an image in mind when the name of Rothko is mentioned. Undoubtedly it will be something very simple, and very abstract. The paintings he gave the Tate are all of the same distinctive kind: large areas of dark, funereal colours, laid together in horizontal bands, clerical grey, say, next to royal purple. There are seldom more than two principal colours, and both tend to become cloudy towards the edge of their own fields.

What could be simpler? Even culpably simple, encouraging in some the notion that this could be one of those famous modern artist’s confidence tricks, designed to make the public see the Emperor’s New Clothes.

Of course, Rothko’s later paintings are not so simple as they may appear at first glance. Rothko himself, who believed in doing rather than talking about doing, once remarked: “I am for the simple expression of complex thoughts,” and there is no mistaking the sheer thought, quite possibly complex, that has gone into the paintings’ creation. But the assumption tends to be that, because this is all we are likely to know of his work, it was all he ever did.

In more recent times we have seen painters who launch from art school with canvases painted one single, uniform colour, or, like Ian Davenport, streaked with vertical lines of colour poured straight from the pot. But that was not the way that an abstract painter born in 1903 would have arrived at his mature style. And though the Tate exhibition gives no real inkling of the fact, before Rothko arrived at his final colour fields, he did a lot of other things along the way.

His father was a Russian-Jewish pharmacist, who emigrated to Portland, Oregon, with his family when Rothko was 10. Initially his son seems to have had little interest in art, studying at Yale with the aim of becoming an engineer or a lawyer. But in 1923 he abruptly abandoned his studies and spent some time with nothing to do but “wander around, bum about, starve a bit”, in New York. If we believe him, he took up art only by chance. “I happened to wander into an art class, to meet a friend who was taking the course. All the students were sketching the nude model – and right away I decided that was the life for me!”

He shortly enrolled in the Arts Students League, New York, where he was taught by the modernist painter Max Weber. Under Weber’s tuition he began to paint rather like early Cézanne, with bulgy, slightly unruly nudes dominating his canvases. Despite Rothko’s avowed reason for entering art school, no one could say that these somewhat rangy ladies are exactly sexy, but they are certainly animated, and suggest that a red-blooded young man is flexing his muscles. The style was very much in the air at the time, and essentially Rothko was following the line of least resistance by swallowing whole the teachings of his first master.

But later in the Twenties, he met and befriended a more modern modernist, Milton Avery, who painted boldly simplified forms in pure, evenly applied colours – a style that had a profound effect on Rothko. From the start his natural tendency was always towards simplification, and his contact with Avery showed him the way to pare down his style, while continuing to apply it to relatively conventional, social-realist themes: ordinary people in a street or a waiting room, still-lifes and occasional portraits, including a self-portrait painted in 1936, which shows him as a rather forbidding figure, with a moustache, sparse beard, and dark glasses.

It is difficult, but not impossible, to see where the Rothko of the late Thirties links up with the iconic Rothko of the Fifties and Sixties. The key is probably to be found in the watch words simplicity and directness. In 1929 he began to teach children in the Brooklyn Jewish Centre, which he continued to do for a decade. He was particularly taken with the directness of children’s vision, and found himself emulating it in a long series of street scenes and interiors, handling the paint with deliberate roughness and shamelessly distorting the figures, slimming them sometimes almost to the point of non-existence, to make his point.

It must have been this aspect of his art which persuaded the WPA (Works Progress Administration), an enterprise of the Roo- sevelt years, that he was a talent suitable to their somewhat populist, liberal projects. Many of the artists in the scheme were set to painting murals in post offices and town halls, but Rothko remained strictly an easel painter. Throughout the Thirties he painted portraits and urban landscapes in a range of dark, heavy colours, with a degree of social commitment true to his statement of belief: “It is a widely accepted notion among painters that it does not matter what one paints as long as it is well painted. This is the essence of academicism. There is no such thing as good painting about nothing.”

Through the Forties, though, from a generally humanist position he underwent a gradual change in the direction of ever greater formalism.

From one point of view the paintings of New York subways he produced almost obsessively at this time may be seen as a continuation of his New Deal, humanitarian attitudes. But while the architecture of the subway, its bold rectangles, increasingly fascinates him, the people in his pictures are gradually drained of individual character, and become mere stereotypes of urban life: the dark-suited businessman, the shopper, the schoolchild . . . Is he losing interest in human beings?

More likely, he is losing faith in them. By the end of the war he has reached something very like despair. He said at the time: “It was with the utmost reluctance that I found the figure could not serve my purposes . . . But a time came when none of us could use the figure without mutilating it.”

By this time Rothko was showing signs of the depression which was to dog the rest of his life. Towards the end of the war he had moved from recognisable scenes with recognisable people to painting in a vaguely Surrealist style. These paintings are not exactly representational but occupy a sort of Miró-like dreamland where the mysterious inhabitants seem to become more and more menacing, until they dissolve altogether into clouds of colour, frequently threatened and disrupted by great blobs and blotches of black.

The move from these vestiges of representation into complete abstraction, which takes place around 1948, seems to constitute almost a sigh of relief. The bright, sometimes pastel colours of these paintings must represent some sort of escape: escape from the the dreariness of the postwar world, as even the victor nations pulled themselves round from total exhaustion, and then the ever-present menace of the atom bomb and the Cold War between Russia, the land of Rothko’s heritage, and America, the land of his present and future. If there was going to be any future – something the Rothko was growing increasingly dubious about.

The new Tate show is very specific: it is strictly about the the colour-field paintings of Rothko’s last few years. Undeniably they are his most important works, so interpretation is inevitable. It is never safe to equate an artist’s work too closely with his autobiography, but it is also worth considering that maybe an artist is the nearer to total nakedness the less he can rely on narrative as a decoy.

Certainly Rothko’s choice of colours seems to reflect in a direct way the state of his emotions at the time of painting. Bright, warm colours, the scarlets and pinks and golds, that dominate his work in the Fifties, seem to betoken a lifting of the spirits, and it must be significant that one of his paintings, dated 1954, is entitled Homage to Matisse, the painter par excellence of this world’s joys. How sad that he could not cling on to this kind of inspiration to the end.

Rothko, Tate Modern, London SE1 (www.tate.org.uk 020-7887 8888), Sept 26-Feb 1.

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