Ronald Aronson praises Jean-Paul Sartre's existential Marxism in an essay in the Boston Review. I argue that existential Marxism is a case of a contradictio in adiecto. Sartre was never recognized as a Marxist by his contemporaries. He not only failed to show any interest in the question of economic exploitation, but most of the answers he gave in the Critique even contradicted Marxist theory. His expression of Marxism as the philosophy of our time seems to have rather been more an act of courtesy than the expression of deep conviction. As Sartre himself later said, Marxism and existentialism are quite separate philosophies.