June 6, 2018:

Also contentious was Althusser's complementary slogan, "Marxism is not a historicism." This must have seemed jarring at the time granted that Marxism is all about history — Gramsci called it "an absolute historicism". Althusser defines "historicism" as the evolutionist conception of time as linear and undifferentiated, "even", contrasting with Lenin's insistence on the unevenness of all processes. Althusser's concept of differential historical time captures the uneven temporal evolution of the various elements of a social formation, which Historicism makes invisible.