One of the best vantage points on the birth of the Weimar Republic is offered by the diaries of Thomas Mann. By the time of World War I, Mann was already one of Germany’s greatest writers, and he took his patriotic role very seriously. He spent the war years writing a tract meant to convince the world, and possibly himself, that his country’s cause was righteous, a defense of earnest German Kultur against deracinated French Zivilisation. In November 1918, as the German Navy mutinied and the government fell, Mann watched with concern, but without panic. “I am content with the relative calm and orderliness with which, for the present at least, everything is taking place,” he wrote in his journal on November 10, the day before the Armistice. “The German revolution is after all German, though nonetheless a revolution. No French wildness, no Russian Communist drunkenness.”

The doom of the Weimar Republic, Eric Weitz argues in “Weimar Germany: Promise and Tragedy” (Princeton University Press, 432 pages, $29.95) was already sealed in the lukewarm revolution that so reassured Mann. In its 14 years of life, Weimar faced enough challenges to bring down even a strong government — defeat in war, traumatic hyperinflation, the Great Depression. But the government of the German Republic was never strong, because it was born in wavering and compromise. The old Imperial Germany of Kaiser Wilhelm didn’t really die on November 9, 1918, when the Kaiser abdicated and the Social Democratic Party leader Philip Scheidemann proclaimed a new government from the balcony of the Reichstag.

The reason for this failure lay in the timidity of Germany’s new, ostensibly socialist government, led by Friedrich Ebert. In the chaos of the war’s last days, Ebert feared that any attempt to remake German society would lead to the complete collapse of the state. The specter of the Bolshevik Revolution, exactly one year earlier, haunted him; “Bolshevik conditions,” such as famine and civil war, had to be avoided at all costs. As a result, while the Social Democrats introduced new labor and social welfare policies, they didn’t take on the powerful props of the old Imperial Reich: the army, the nobility, the senior bureaucracy, the judiciary, and the church. All of those groups, and millions of traumatized, disappointed Germans, never truly accepted the Republic as a legitimate government. They shared the reactionary bloodthirst of Oswald Spengler, who wrote: “We need some harsh punishments … until the time is right for that small group … to be called to leadership: Prussian nobles and Prussian officials.” When the time came, of course, it wasn’t the conservative old Junkers, but the low-caste, radical Nazis, who would benefit from Weimar’s collapse.

From the beginning, Mr. Weitz explains, Weimar was handicapped by “a contested legacy, a deeply divided civic and political culture.” Yet the central insight of Mr. Weitz’s book is that those divisions also produced the vibrant intellectual life whose products we still cherish today. As Mr. Weitz writes, “Sedate, somnambulant, self-satisfied societies — and there are such things — do not question, do not probe.” That is why the name Weimar has always carried a double charge. In politics, it means an incurable disease, a state divided against itself, a habit of hatred and assassination; in culture, it means fruitful transgression, the gratified shock of the modern. By showing how these two sides belong to the same coin, “Weimar Germany” serves as a perfect introduction to its subject.

Reading Mr. Weitz, it becomes clear that many of the challenges that brought down the Weimar Republic were by no means specific to Germany. In the 1920s, for instance, Germans spent a lot of time debating gender and sexuality. They experimented with nudism — Mr. Weitz reproduces photos from the homoerotic best-seller “Man and Sun” — and they worried about the independent “New Woman” — who, in the words of one journalist, “operates matter-of-factly; she works; she takes pleasure as we do.” Yet America, too, had its Roaring ’20s, its flappers, and its jazz babies. Here, too, burlesque shows and titillating movies became more respectable than ever before.

The difference was that, in Germany, the tensions of modernism could be seen as simply the poisoned fruit of defeat and revolution. The Weimar Republic, its enemies argued, was responsible for nothing but abominations — from the Treaty of Versailles, to the defiant architecture of the Bauhaus school, to the confrontational theater of Brecht and Weill. The abolition of old gender roles fit the pattern perfectly. As a Catholic group declared in 1929, “The decay of the family and the decay of the state are inseparable.” The same logic fueled the Nazi program: abrogating the hated treaty and banning “degenerate art” were part of the same impulse.

It is always the metropolis that reactionaries and puritans hate the most, and so it was Berlin that became the symbol of everything decadent in Weimar Germany. “Berlin is not Germany,” proclaimed one writer quoted by Mr. Weitz. To another, the capital was “the cesspool of the Republic,” harboring “all too many Slavs and all too many altogether uninhibited East European Jews.” Yet today, Weimar Berlin is cherished by many as a world capital of modernism. Mr. Weitz devotes a whole chapter to an imaginary walking tour of the city, pointing out the cafes and cabarets and political posters. In Berlin in the 1920s, you could attend the premiere of “The Threepenny Opera,” read Walter Benjamin and Joseph Roth in the newspaper, or see Fritz Lang filming at the UFA Studios. Mr. Weitz is especially interested in architecture, and writes at length about the modernist housing projects of Bruno Taut and the sleek department stores of Erich Mendelsohn: “A new, innovative architecture, rooted in the conditions of modernity, they believed, would surmount the fragmentation of contemporary life.”

In an ideal world, such creativity might have healed the fractures of Weimar Germany. But the years between 1918 and 1933 were some of the least ideal in German history. In 1923, at the height of the inflation, it took 4.2 trillion marks to purchaseanAmericandollar. Pensioners went bankrupt, and workers were paid twice a day, so they could buy food before the price went up again. In 1930, the Great Depression hit Germany harder than any other country, leaving 40% of the workforce jobless. If “the economy is destiny,” in the words of Germany’s foreign minister, Walter Rathenau, then Weimar’s destiny was hopeless. And all along there was the drumbeat of political violence — attempted coups, street fights between Nazis and communists, and assassinations, including Rathenau’s.

The man who finally killed the Weimar Republic, of course, was Adolf Hitler, who became Chancellor on January 30, 1933. But if Hitler was the occasion of its death, the root cause was deeper and less tangible. The Weimar Republic, one might say, died from too much argument. “When virtually every debate becomes a liveor-die question about the essential features of human existence, from the intimacy of the bedroom to the structures of the business world,” Mr. Weitz writes, “when there is no overarching system of belief to which most people give their loyalty, a democracy cannot long endure.” Weimar reminds us, in our very different and much luckier democracy, to appreciate the American consensus that makes dissent possible.

akirsch@nysun.com