IN JUNE OF 1920 the 22-year-old Bertolt Brecht began keeping a diary and continued to make entries in it for nearly two years. The book only came to light a few years ago in Germany. Though something less than a rich windfall for students of Brecht, it's rather more than a document of casual interest. Its chief value intellectually is the random insights it gives into Brecht's initially disorderly movement towards his assured powers and, personally, the revelations it offers of his turbulent psychic state during this time.

When he started the diary Brecht had already written Baal and was finishing Drums in the Night, which several years later would bring him immediate fame. But he was known now only as a poet to a small circle of friends and admirers in his hometown of Augsburg and in nearby Munich. The diary covers a crucial period, then, a time when he is full of ideas and ambitions, sorting out his belligerent opinions and developing a style. It is a time, too, when his personal life is in chaos; he has already had an illegitimate child, is involved sexually with several other women and is continually chafing under a lack of money. It isn't surprising that, as Willett says, he was "never again [to be] so openly interested in himself."

He is obsessed with a sense of being raw, indefinite, "unfinished." He looks in the mirror and sees "my idiodic face...it contains many elements of brutality, calm, slackness, boldness and cowardice, but as elements only, and it is more changeable and characterless than a landscape beneath scurrying clouds." Another time he writes: "And what am I? An impertinent little packet, you can't see ny face yet, a certified promise, and what does that bring in?" He is being pressed by one of his lovers to marry her and writes: "I can't...I must have elbowroom, be able to spit as I want, to sleep alone, be unscrupulous...I am strictly provisional and need room to take off, I'm still growing."

He is clearly growing intellectually and as an artist. Although the diary has a number of entries displaying a youthful brashness and disdain - "How this Germany bores me! .... A degraded peasantry...a middle class run to fat; and drab intellectuals" - they are outweighed by observations that testify to a much less complacent sense of his own condition. He scolds himself for scattering his talents (besides writing plays and poems, he has half a dozen film projects going and as many get-rich-quick schemes outside the arts), for not being able to finish Drums in the Night satisfactorily, and for what he thinks of as the "softness" of Baal.

But he keeps getting "insights into the true nature of great art." Softness, "polish" are what he swears to avoid. "One needs to beware of 'wit,"" he writes, "of candied fruit, tasteful decorations and smooth finish." And, in a foreshadowing of a future dramaturgical principle, he says that "the clearer the details of a character, the thinner the connection with the observer." More and more he sees the need to break through convention, to reject in his art the accumulations of culture, accepted and sanctified modes of utterance. "O God," he writes, "please let my sight always cut through the crust, pierce it!"

The diary tells us a good deal about his reading during the period. Among his German contemporaries he admires only the Expressionist playwright George Kaiser and the novelist Alfred Doblin. But he reads with pleasure a heterogeneous lot of foreign writers: Kipling, from whom he will take material for A Man's a Man; Upton Sinclair, whose The Jungle will be a source for St. Joan of the Stockyards; G. K. Chesterton, whose Father Brown stories impress him with British "rationality." And apart from books he is "devastated by the cinema," especially by Chaplin, whose films were first shown in Germany only in 1921.

Perhaps the most valuable element in the book is Brecht's comments on In the Jungle of Cities, one of his greatest plays, on which he has begun work. "Nobody has yet described the big city as a jungle," he writes. "Where are its heroes, its colonisers, its victims? The hostility of the big city, its malignant stony consistency, its babylonian confusion of language - in short its poetry has not yet been created."

He writes of the play that "one thing is present...the city. Which has recaptured its wildness, its darkness and its mysteries. Just as Baal is a song of the countryside, its swansong." And he offers a central piece of advice to future directors: "The scenes should be performed quite lightly, on a makeshift stage against a background of pasteboard and water-colour, lightly knocked together." Already, at this early moment in his great career, he has gained the freedom from theatrical expectations, the rich informality, that will be a mark of his practice from now on.