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.
Karl MarxThe Communists disdain to conceal their views and aims. They open declare that their ends can be attained only by the forcible overthrow of all existing social conditions. Let the ruling classes tremble at a Communistic revolution. The proletarians have nothing to lose but their chains. They have a world to win. WORKING MEN OF ALL COUNTRIES, UNITE!
Karl Marx