The Dreyfus Affair sharply outlined traits that later defined twentieth-century politics.

Evidence

We are here concerned essentially with the political bearings of the Dreyfus Affair and not with the legal aspects of the case. Sharply outlined in it are a number of traits characteristic of the twentieth century. Faint and barely distinguishable during the early decades of the century, they have at last emerged into full daylight and stand revealed as belonging to the main trends of modern times. — Hannah Arendt, The Origins of Totalitarianism, 285