Labour is the source of all wealth, the political economists assert. And it really is the source -- next to nature, which supplies it with the material that it converts into wealth. But it is even infinitely more than this. It is the prime basic condition for all human existence, and this to such an extent that, in a sense, we have to say that labour created man himself.
Friedrich EngelsFreedom does not consist in any dreamt-of independence from natural laws, but in the knowledge of these laws, and in the possibility this gives of systematically making them work towards definite ends.
Friedrich EngelsJust as Darwin discovered the law of evolution in organic nature, so Marx discovered the law of evolution in human history; he discovered the simple fact, hitherto concealed by an overgrowth of idealogy [sic], that mankind must first of all eat and drink, have shelter and clothing, before it can pursue politics, science, religion, art etc.
Friedrich EngelsWe discovered that in connection with these figures the German national simpletons and money-grubbers of the Frankfurt parliamentary swamp always counted as Germans the Polish Jews as well, although this dirtiest of all races, neither by its jargon nor by its descent, but at most only through its lust for profit, could have any relation of kinship with Frankfurt.
Friedrich Engels