" The sum of productive forces, capital funds and social forms of intercourse, which every individual and generation finds in existence as something given, is the real basis of what the philosophers have conceived as "substance" and "essence of man," and what they have deified and attacked: a real basis which is not in the least disturbed, in its effect and influence on the development of men, by the fact that these philosophers revolt against it as "self-consciousness" and the "Unique. "

― Karl Marx , The German Ideology / Theses on Feuerbach / Introduction to the Critique of Political Economy