The focus of all life is its economy, the mode through which every living creature produces its material existence. I know no other criterion for the evaluation of social life except that of social economy. In society, just like anywhere else, the mode of production is the focus around which revolve all the modes of life: in the historical life of conscious beings, it is also the focus of all modes of consciousness.

Hess to Herzen, March 1850, Briefwechsel p. 253 - Hess' Diary