Durant’s book was published in 1926, and so none of its subjects were born in the 20th century (the youngest, Bertrand Russell, was born in 1872). Among 20th-century European philosophers, the Germans once again loomed large, but for the worst of reasons. Two of Germany’s greatest minds, Carl Schmitt and Martin Heidegger, lent their immense intellectual weight to the Nazi regime, Schmitt as a jurist and Heidegger as the rector of a prominent university.

Other Germans, especially Jewish Germans, had their worldview irrevocably shaped by experiencing the Nazi regime and the Holocaust, directly or indirectly. Theodor Adorno and other members of the Frankfurt School wrestled with the political and social implications of the rise of totalitarianism. Hannah Arendt traveled to Jerusalem for the trial of Adolf Eichmann, a major Nazi official kidnapped by Israeli officials. His trial led her to coin the term “the banality of evil” in her work Eichmann in Jerusalem (1963) to describe moral collapse as a matter of bureaucratic routine rather than sadism.

World War II cast a long shadow over non-Germans as well. The Frenchman Jean-Paul Sartre had been a prisoner of war and then lived under Nazi occupation in France, experiences which helped inform his embrace of existentialism, emphasizing the absurdity and often pointless cruelty of life.