Just 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 EngelsThe state is nothing but an instrument of opression of one class by another - no less so in a democratic republic than in a monarchy.
Friedrich EngelsThe slave frees himself when, of all the relations of private property, he abolishes only the relation of slavery and thereby becomes a proletarian; the proletarian can free himself only by abolishing private property in general.
Friedrich EngelsIn a political struggle of class against class, organization of trade unions is the most important weapon.
Friedrich EngelsLabour 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 Engels