Marx on Labor and Nature

"Labor is not the source of all wealth. Nature is just as much the source of use values ... as labor, which itself is only the manifestation of a force of nature, human labor power.... And insofar as man from the beginning behaves toward nature, the primary source of all instruments and subjects of labor, as an owner, treats her as belonging to him, his labor becomes the source of use values, therefore also of wealth.... [P]recisely from the fact that labor depends on nature it follows that the man who possesses no other property than his labor power must, in all conditions of society and culture, be the slave of other men who have made themselves the owners of the material conditions of labor. He can only work with their permission, hence live only with their permission."

--Karl Marx, Critique of the Gotha Program, Part 1