... And now as to myself, no credit is due to me for discovering the existence of classes in modern society or the struggle between them. Long before me bourgeois historians had described the historical development of this class struggle and bourgeois economists, the economic economy of the classes. What I did that was new was to prove: (1) that the existence of classes is only bound up with particular historical phases in the development of production (historische Entwicklungsphasen der Production), (2) that the class struggle necessarily leads to the dictatorship of the proletariat, (3) that this dictatorship itself only constitutes the transition to the abolition of all classes and to a classless society . Ignorant louts like Heinzen, who deny not merely the class struggle but even the existence of classes, only prove that, despite all their blood-curdling yelps and the humanitarian airs they give themselves, they regard the social conditions under which the bourgeoisie rules as the final product, the non plus ultra [highest point attainable] of history, and that they are only the servants of the bourgeoisie. And the less these louts realize the greatness and transient necessity of the bourgeois regime itself the more disgusting is their servitude....
Letters: Marx to J. Weydemeyer in New York [abstract]