It is trivially true that the history of all hitherto existing society has been a history of molecular configurations in motion, or of the stimulations of human beings by pains and pleasures of the most diverse sorts, or of any one of a number of nearly inexhaustible sets of alternative descriptive categories. Marx chose, in the opening sentence of the main text of The Communist Manifesto, to focus on class-struggle as a leitmotif throughout recorded human history, and in the bulk of his published writings about current affairs and the capitalist economic system he returned repeatedly to the most virulent manifestation of contemporary class-struggle, the opposition between the bourgeois and proletarian classes. In short, Marx's philosophy of history and social philosophy, which in the final analysis are inseparable from one another, are highly complex and flexible, rather than, as the facile criticisms would have it, simplistic and dogmatic.