Hannah Arendt would have eviscerated the title of “The Origins of Totalitarianism” had she not been the book’s author. Though published in 1951, it is still the most influential work on the worst of Europe’s 20th-century horrors. Yet contrary to its title’s claim to uncover “origins,” Arendt would have insisted that all efforts to speak in such clear-cut terms about causality were bound to be reductive, alien to the true pulse of history. “Not only does the actual meaning of every event always transcend any number of past ‘causes’ which we may assign to it,” she wrote in an essay appearing shortly after her magnum opus, “this past itself comes into being only with the event itself.”

For years now, the German historian Gotz Aly has been looking for causes. In densely documented book after book — packed with the bureaucratic memorandums that are the core of his evidentiary universe — he has sought “to discern the utilitarian goals behind the murder of the European Jews.” Aly is an earnest, tireless compiler of the often arcane or overlooked, yet there is something raw, never quite finished, if always usefully suggestive, in his approach.

It was the goal of robbing Jews of their wealth that dominated his early research. Later, “Why the Germans? Why the Jews?” would identify a stultifying envy of Jews, wealthy or not, as the prime motive of the Holocaust, the infuriating sense in Germany and elsewhere, too, that Jews, in the words of Maxim Gorky, were “obviously better, more adroit and more capable.”

Now in his most ambitious effort, “Europe Against the Jews: 1880-1945,” which is billed as a “prehistory of the genocide,” Aly elaborates on the thesis that the Nazi effort to eradicate an entire people is explainable as “rational,” if, of course, also deplorable. He now sees the origins of the Holocaust in the consolidation of nationalism around the turn of the 20th century. Above all, the welter of new nation-states to emerge from the slaughterhouse of World War I is identified as the essential station on the road to ethnic cleansing, and worse.