Labour is ... not the only source of material wealth, i.e, of the use-values it produces. As William Petty says, Labour is the father of material wealth, the earth is its mother.
Labour is ... not the only ...
Quotes from the same author
Under private property, each tries to establish over the other an alien power, so as thereby to find satisfaction of his own selfish need. The increase in the quantity of objects is therefore accompanied by an extension of the realm of the alien powers to which man is subjected, and every new product represents a new potentiality of mutual swindling and mutual plundering.