How Arthur Koestler embodied the 20th century.

History is a brutal sieve. Arthur Koestler is remembered now—if at all—for writing Darkness at Noon, a hand grenade of a novel tossed at Joseph Stalin's Kremlin. Those 200 pages are all we retain of an intellectual nomad who stormed across the 20^th century. He seems to have been everywhere, like an angry, book-spewing Zelig. Even a thumbnail summary makes me feel exhausted (deep breath): He grew up in the last days of the Austro-Hungarian Empire, witnessing revolutions and counter-revolutions. He was one of the first Zionist settlers in Palestine. He became a star in the Berlin of Sally Bowles' cabarets and a rising Adolf Hitler. He was jailed and nearly shot by Gen. Franco. He fled the Nazis through Casablanca, Morocco. He gave Albert Camus a black eye, George Orwell a holiday home, and Soviet communism an enema. He had sex with supermodel twins, took magic mushrooms with Timothy Leary *, and helped create Intelligent Design. Oh—and he was a rapist.

Michael Scammell's terrific new biography—Koestler: The Literary and Political Odyssey of a Twentieth-Century Skeptic—scrapes together a contradictory life that amounts to far more than the single novel that keeps him on our bookshelves. George Steiner said of him: "There are men and women who seem to embody the times in which they live. Somehow their biographies take on and make more visible to the rest of us the shape and meaning of the age." This is truer of Koestler than Scammell knows. He was not a "skeptic" at all. Like the century he embodies, he skipped from one utopian fantasy to another, drinking the dream dry and then tossing it aside with disgust. Yes, he glimpsed darkness at noon—but he always saw another blinding light at 2 p.m. His life is a parable about the dangers of utopianism—and why it will always leave you with a vomit-flecked hangover.

Koestler was a 5-foot-6-inch cocktail of raw nerve endings and neat booze, prone to hurling restaurant tables across the room if you argued with him over dinner. He was born in 1905, and he nearly killed his mother there and then. She was 34—a seriously old age at that time to have your first child. The labor took two agonising days. Koestler liked later to claim his family had flared up from nothing into sudden wealth and then vanished into exile or the gas chambers. It wasn't true: His mother was from one of the richest Jewish families in Austro-Hungary. But Koestler wanted to deny everything about her, always. She was ill and depressive, and even trips to Sigmund Freud couldn't iron her out: She said he was "a pervert." Her sniping rejections of her son—and her abandonment of him for years as she went off on "rest cures"—created in him a sense of guilt and inferiority that became his conjoined twin.

He was a sullen, friendless boy, passively absorbing all the anti-Semitic hatreds of the time and turning them on himself. It was only in his late teens that he found his first true family: He joined the Jewish frat-houses of Vienna. He compared their bouts of drinking and duelling to group therapy, stripping away his shyness. But in his university, Jews were being beaten with sticks by angry mobs howling "Jews out!" Then, one day, a visiting doctor delivered a lecture saying there was a new world waiting for the Jews, to be built in Palestine. It was to be Koestler's first intellectual intoxication.

The template for all his ideological intoxications begins here, with the promise of a promised land. As he wrote later: "To say that one had 'seen the light' is a poor description of the mental rapture which only the convert knows. … The new light seems to pour across the skull. … There is now an answer to every question. Doubts and conflicts are a matter of the tortured past—a past already remote, when one had lived in dismal ignorance in the tasteless, colorless world of those who don't know."

He saw the creation of Israel as a cure for his Jewishness, which he regarded as a curse. He raged against the "intelligent monkey face" of Jews with "thick, curved noses, fleshy lips and liquid eyes," saying they resembled the "masks of archaic reptiles." Only in their own country—away from the paralyzing ghettos of Europe—could Jews become "normal." Characteristically, he immediately converted to the most hardcore strain of Zionism available—one preached by Vladimir Jabotinsky, who demanded the immediate bombing of British imperial forces in Palestine and the total ethnic cleansing of Arabs from the river to the sea. The very act of fighting would redeem the "effeminate" Jews.

Koestler charged off to Palestine—but the recoil was immediate. He wrote: "I found myself in a rather dismal and slumlike oasis in the wilderness consisting of wooden huts surrounded by dreary vegetable plots." He was a frat boy sent to dig cabbage patches for the settlers. They soon rejected him, and he grew bored. "I had gone to Palestine as a young enthusiast," he said, but instead of the Promised Land, "I had found reality, an extremely complex reality which attracted and repelled me." He could see that innocent Palestinians lived there and didn't deserve to be driven out of their homes—but he shunted this aside, saying he would develop "schizophrenia" if he thought about it too much. On a steamship home, he met a girl who told him there was another promised land waiting—and its messiah was named Lenin.

There is a bizarre doubleness to Koestler. He can always see—with clinical precision—why he was wrong to be swept away by the last ideology, even as he is hurtling into the next. He went to the Soviet Union and trained himself not to see. Yes, the starved famine victims lay slumped all around, dying in their millions. Yes, the prisons he glanced at were full of innocents. But he went home and wrote a passionately pro-Soviet book that didn't mention them once. The Soviet Union promised a Paradise beyond scarcity or pain. That vision, conjured in words, seemed more real to him than the actual country screaming into his ear.

Like so many intellectuals of his generation, he flocked to the Spanish Civil War, an apocalyptic showdown between the left and fascism. When the Republican troops fled from Malaga, he stayed to witness their arrival—a moment of real courage—and was captured. In Franco's dank cells, he experienced a transformation: He saw the importance of individual freedom for the first time. When he was released, he met with a friend in France who had been held in a Soviet jail—and saw it as an epiphany when he realized her experience under communism was exactly the same as his under the fascists.

He became, in a sudden stride, one of the great left-wing opponents of communism. In a fever, he wrote Darkness at Noon, the story of a senior revolutionary who is jailed and is so convinced by the rightness of the cause that he accepts his own execution—even though he had done nothing. It was the story of the show trials, as told from within. He was describing his own turmoil from the inside. Koestler was always at his best when he was experiencing an ideological collapse: He could, for a moment, be honest and describe things as he experienced them. As France fell to the Nazis, Koestler was detained again and escaped again.