According to the materialist conception of history, the ultimately determining factor in history is the production and reproduction of real life. Neither Marx nor I have ever asserted more than this. Hence if somebody twists this into saying that the economic factor is the only determining one, he transforms that proposition into a meaningless, abstract, absurd phrase. The economic situation is the basis, but the various elements of the superstructure – political forms of the class struggle and its results, such as constitutions established by the victorious class after a successful battle, etc., juridical forms, and especially the reflections of all these real struggles in the brains of the participants, political, legal, philosophical theories, religious views and their further development into systems of dogmas – also exercise their influence upon the course of the historical struggles and in many cases determine their form in particular. There is an interaction of all these elements in which, amid all the endless host of accidents (that is, of things and events whose inner interconnection is so remote or so impossible of proof that we can regard it as non-existent and neglect it), the economic movement is finally bound to assert itself. Otherwise the application of the theory to any period of history would be easier than the solution of a simple equation of the first degree.
We make our history ourselves, but, in the first place, under very definite antecedents and conditions. Among these the economic ones are ultimately decisive. But the political ones, etc., and indeed even the traditions which haunt human minds also play a part, although not the decisive one.
Engels to Joseph Bloch in Königsberg; London, September 21[-22], 1890, Marx Engels, Selected Correspondence, Progress Publishers, Moscow, 1982, 394-395
Preparing for the first redivision of the world as areas of exploitation.
materialism, mysticism and art 
