Economic and Philosophic Manuscripts of 1844
" ... Marx explains how, under capitalism, people rely on labor to live. In the past people could rely on nature itself for their natural needs; in modern society, if one wants to eat, one must work: it is only through money that one may survive. Thus [a person] becomes a slave to his wages. It is only through his work that he can find enough money to continue to live; but he doesn't simply live, he actually only survives, as a worker. Labor is only used to create more wealth, instead of achieving the fulfillment of human nature."