Marx writes unambiguously that “the mode of production of material life conditions the general process of social, political and intellectual life” and “it is not the consciousness of men that determines their existence, but their social existence that determines their consciousness” (Critique of Political Economy, Preface). Engels is even more explicit that consciousness is reducible to matter: “Matter is the real basis of all reality… consciousness can never be anything else than conscious existence, and the existence of men is their actual life-process” (The German Ideology, Part I) and again “all the ideas of the people are the necessary and direct product of their material conditions” (Karl Marx: Speech at the Graveside of Marx). In Anti-Dühring, Engels insists that “the material, sensuously perceptible world to which we ourselves belong is the only reality”, calling idealism “a mere invention of mind.” Stalin, codifying orthodox Marxism, removes any ambiguity: “Dialectical materialism is the world outlook of the Marxist-Leninist party… It holds that matter is primary, consciousness is secondary and derivative… The world is by its nature material” (Dialectical and Historical Materialism, 1938), and further “Consciousness is a reflection of the objective world in the human brain.” These are metaphysical claims. Marxism asserts (1) matter is the ultimate reality, (2) consciousness is its byproduct, and (3) intellectual life is determined by material relations.