THE REVOLUTIONIST.

The Russian radical writer and philosopher Alexander Herzen loved Rome for its warmth and spontaneity, but he was a little chagrined to find himself there when the revolution of 1848 erupted in Paris, seven hundred miles away. Luckily, the Romans were equal to the event. As Herzen watched, they gathered at the embassy of the oppressive Austrians, pulled down the enormous imperial coat of arms, stomped on it, then hitched it to a donkey and dragged it through the streets. "An amazing time," Herzen wrote to his Russian friends. "My hand shakes when I pick up a paper, every day there is something unexpected, some peal of thunder." He raced to Paris, where the provisional government was handing out grants, like some gonzo arts foundation, to anyone willing to spread the revolution abroad. Herzen's old friend the anarchist Mikhail Bakunin had already started east to foment revolution against the Tsar; another friend, the German Romantic poet Georg Herwegh, was raising a battalion of emigre workers and intellectuals to march on Baden-Baden. Herzen stayed in Paris to see what would happen next.

Nothing good, as it turned out. The liberal provisional government, challenged by the radical Paris workers, called in the National Guard and unleashed a slaughter. Bakunin was arrested in Dresden, commencing a long journey through the prisons of Europe. And Herwegh's battalion was routed by the Prussian Army outside Baden-Baden, the poet returning to Paris in disgrace. "Our hero could no more bear the smell of gunpowder," his rival Heinrich Heine jeered, "than Goethe could that of tobacco." Within a few months, the revolutionary tide had rolled back all across Europe.

Herzen, heartbroken by the developments, announced that he was turning inward: if society was not ready to be liberated from a crumbling order, individuals could at least save themselves, as he put it, "from the danger of falling ruins." He and Herwegh began to discuss plans for a two-family commune. The events of 1848 had left the Herweghs without resources, but Herzen had managed to get his assets out of Russia, foiling the Tsar's attempt to seize them. "Money is independence and power, it is a weapon," he explained, unapologetically. "And no one throws away a weapon in time of war, even if it comes from the enemy and is a little rusty." He found the two families a house in Nice, and together they moved there in the middle of 1850. Herzen was unaware that six months earlier his beloved wife, Natalie, had begun a serious affair with Herwegh.

On the day that Herzen finally learned about it, he found himself standing with Herwegh on a sheer rock cliff overlooking the sea at Nice. He was out of his mind with rage. "Why didn't I immediately start a conversation or push him off the bluff into the sea?" he later wondered. He'd been betrayed by Herwegh--but how, exactly? Didn't he believe that people should break away from traditional bonds of family and religion? That the old world was dying? And how, assuming that Herwegh was unequivocally at fault, was Herzen to take revenge? He was an aristocrat, and aristocrats--Pushkin, for example--fought duels, but Herzen believed that duelling was barbaric. Lamely, he asked Herwegh whether he'd read a certain novel by George Sand; Herwegh claimed not to remember, and slithered off to the bookshop. It was the last they saw of each other.

What happened next--in a cascade of vicious letters, letters in response, unopened letters, letters that were claimed to have been unopened, and letters spread around Nice and Zurich and Geneva--became a major scandal on the European left. It seemed to carry a lesson about the dangers of the new ideas. The German socialist Arnold Ruge wrote a five-act verse drama, "The New World," based on the events; Marx gossiped about them to Engels. Herwegh told everyone who would listen that Herzen was keeping Natalie against her will; Herzen defended himself to his allies in the revolutionary movement. "I belong to the new society to which you and your friends belong," he wrote to the French anarchist Proudhon. "I belong to the revolution to which Mazzini and his disciples belong." They responded warmly, politely. But what could they do?

The episode is both awful and absurd. Even Tom Stoppard's ...