Dreyfus was convicted on the evidence of handwriting identified as a “self-forgery,” and a single initial in a playful lover’s note. LEONARD DE SELVA/CORBIS

On a January day in Paris, in 1895, a ceremony was enacted in the courtyard of the École Militaire, on the Champ-de-Mars, that still shocks the mind and conscience to contemplate: Alfred Dreyfus, a young Jewish artillery officer and family man, convicted of treason days earlier in a rushed court-martial, was publicly degraded before a gawking crowd. His insignia medals were stripped from him, his sword was broken over the knee of the degrader, and he was marched around the grounds in his ruined uniform to be jeered and spat at, while piteously declaring his innocence and his love of France above cries of “Jew” and “Judas!” It is a ceremony that seems to belong to some older, medieval Europe, of public torture and autos-da-fé and Inquisitions.

Yet it took place in the immediate shadow of the monument of modernity, the Eiffel Tower, then six years old, which loomed at the north end of the Champ-de-Mars. The very improbability of such an act’s happening at such a time—to an assimilated Jew who had mastered a meritocratic system and a city that was the pride and pilothouse of civic rationalism—made it a portent, the moment where Maupassant’s world of ambition and pleasure met Kafka’s world of inexplicable bureaucratic suffering. The Dreyfus affair was the first indication that a new epoch of progress and cosmopolitan optimism would be met by a countervailing wave of hatred that deformed the next half century of European history.

The Dreyfus affair never goes away, and is the subject of a brave new book by the novelist and lawyer Louis Begley, “Why the Dreyfus Affair Matters” (Yale; $24). Brave because Begley wants to use the occasion not for French-bashing, or for reciting the enduring history of European anti-Semitism, bleak as it is, but as a pointed warning and reminder of how fragile the standards of civilized conduct prove in moments of national panic. The Dreyfus affair matters, he believes, because we have, in the past decade, made our own Devil’s Island and hundreds of new Dreyfuses—the Dreyfus affair matters because we’re still in the middle of it. Begley, as he recounts the story of the Parisian fin-de-siècle legal drama, also spends many pages showing that among the prisoners in places like Guantánamo are many Dreyfuses—innocent, as he was, and, on the whole, much worse treated. He wants to arraign Americans, and particularly those who fetishize the Dreyfus case without grasping its principles: that every accused person should be able to face his accusers in a fair trial, and that national panic makes bad policy and false prisoners.

Yet a parallel can be potent without being, point by point, persuasive: Dreyfus was not the Faceless Foreigner but the Enemy Within. Far from being faceless, he was all face: the haters never tired of describing and drawing his hideousness. “His face is grey, flattened and base, showing no sign of remorse . . . a wreck from the ghetto,” the journalist Léon Daudet wrote. That hideous degradation ritual is at the heart of the Dreyfus affair; it was meant to be public and demonstrative—this is what happens to faithless Jews. The degradation of the prisoners at Guantánamo was essentially private and utilitarian: talk or we’ll subject you to unspeakable humiliations.

The Dreyfus affair matters not because of the parallel with our time but because it was one of the first tests of modern pluralist liberalism and its institutions—a test that those institutions somehow managed to pass and fail at the same time. In France a century ago, the system finally worked, as they used to say after Watergate. The good guys rallied around, the courts did their job, Dreyfus was vindicated and came home to his family. Yet what the system exposed as it worked was, in a way, worse than the injustice it remedied. It showed that a huge number of Europeans, in a time largely smiling and prosperous, liked engaging in raw, animal religious hatred, and only felt fully alive when they did. Hatred and bigotry were not a vestige of the superstitious past but a living fire—just what comes, and burns, naturally.

The typical modern media melodrama involves the courtroom: from Scopes to O.J., the dramatic proscenium of a trial gives structure to the spectacle of modern life. The Dreyfus affair, in some ways the first of those dramas, held France spellbound in part because it included not one but at least six trials; to keep track of them—the trials and courts-martial of Dreyfus defenders and accusers, as well as his own—is exhausting. Just last year, though, George R. Whyte published in paperback his remarkably complete documentary compendium, “The Dreyfus Affair: A Chronological History” (Palgrave-Macmillan; $37); the best extended narrative in English is still Michael Burns’s account in “Dreyfus: A Family Affair,” published back in 1991.

Alfred Dreyfus came from Alsace, which was part of his luck and then part of his tragedy. In 1870, the armies of Prussia and Germany invaded France and routed the government of Napoleon III. As spoils of war, the Prussians took most of Alsace and Lorraine, the northeastern provinces; the figure of Strasbourg in the Place de la Concorde was draped in black (and remained that way until after the First World War). This meant that the Jews of Alsace were both frustrated foreigners and beloved native sons. Even though Alsace and Lorraine were only dubiously “French” in the first place, their loss drove Frenchmen mad.

Above all, many Frenchmen thought that France had lost the war because it had turned away from the faith. For the Paris of Dreyfus’s time was really a city of two towers—across the city from the Eiffel Tower, the Basilica of Sacré-Coeur, with its monumental bell tower, had been slowly rising since the eighteen-seventies, as a sort of counter-monument, done in a gargantuan Romanesque manner then seen as the true mystical style of Franco-Catholicism. It was dedicated explicitly to the expiation of the sins of 1870 and the redemption of France by a restored Catholic Church. Apollinaire used the two towers—one the shepherd of modern life, the other the fountain, the bleeding heart of the past—to structure his vision of the city in his great poem on Paris, “Zone.”

A saner response to the war had been to reform and democratize the French Army, by making its officer ranks meritocratic and national rather than aristocratic and narrow. Dreyfus, as a Jewish son of Alsace, took advantage of these reformist impulses, and came to Paris to become an artillery officer.* He did not fit the model of the traditional duelling and debauching officer, all scars and debts, but represented a new model, of the officer as bourgeois family man. He eventually settled with his wife and two children in a grand apartment on the Avenue du Trocadéro.

It was in that city of two towers, one finished and one rising, that, in the fall of 1894, Dreyfus became the accidental victim of a stupid plot, which was not, in its origins, anti-Semitic. The French Section de Statistique—the Army’s intelligence service—had an agent within the German Embassy: a cleaning woman who every night emptied the wastebaskets of the military attaché, Lieutenant Colonel Maximilien von Schwarzkoppen, and brought the torn-up papers to her government. From the scraps, the spies reassembled a shocking memorandum, the bordereau, in which a French officer offered to sell military secrets. The nature of the secrets to be sold seemed to point to an artillery officer, and suspicion fell on Dreyfus, not least because he made regular visits to his family in Mulhouse, then still in German hands. With the normal prejudice of the secret police in favor of their own suspicions, the Statistique had Dreyfus arrested. As always, pseudo-science came to the aid of paranoia: the Statistique called on a “graphologist” for an opinion, and he testified that the lack of resemblance between Dreyfus’s writing and that of the bordereau was proof of a “self-forgery,” and prepared a fantastically detailed diagram to demonstrate that this was so.