When Jean-Paul Sartre called Marxism “the untranscendable philosophy of our time,” he was the leading existentialist-cum-Marxist philosopher in France. His Critique of Dialectical Reason ran to some eight hundred pages and was meant to be the introduction to what would surely have been his magnum opus, marrying his existentialist philosophy with Marxism. Could the radical subjectivism of existentialism be coupled successfully with a single interpretation of history—the collective struggle of the proletariat against the bourgeoisie, ushering in the classless socialist utopia? Hardly commented on today, Sartre's work attracted the attention of his intellectual friend-turned-enemy Raymond Aron, who penned a brilliant response, History and the Dialectic of Violence, which he considered one of his own favorite works, serving as the first volume of a planned trilogy that would examine the phenomenology of history and analytical philosophy before concluding with an introduction to action within history.

The cause for all of these intellectual fireworks in the twentieth century was the spirit of Karl Marx, who died on March 14 (on the same day Aron was born in 1905), exactly one century before Aron's death in 1983. Where the twentieth century consciously inherited the teachings of Marx in both politics and academia, the twenty-first century has done so unconsciously. Social justice, with its emphasis on inequality and vindicating an oppressed group of people, has roots in Marx's disdain of inequality and his support for the proletarian class over the bourgeoisie. The overriding concern with the economy above all else—“it's the economy, stupid”—reflects the Marxian obsession with socioeconomic factors as the drivers of politics and much else. Connected to this is the general negativity, traditionally the preserve of the Left but today increasingly echoed on the Right, in regards to capitalism as an economic system, charged with everything from increasing inequality and exploitation to ignoring our spiritual needs as humans.