“The truth is that Marxist theory finds complex interactions to exist between what Marx called economic foundation (the sum total of the relations into which men enter to carry on on social production) and the ideological superstructure (the legal, political, religious, aesthetic and philosophical systems of ideas and institutions) which may develop on the basis of that foundation. As Engels wrote “Political, juridical, philosophical religious, literary, artistic, etc., development is based on economic development. But all these react upon one another and also upon the economic base. It is not that the economic position is the ‘cause and alone active’, while everything else only has a passive effect. There is, rather, interaction on the basis of the economic necessity, which ‘ultimately’ always asserts itself. (F. Engels, Letter to Heinz Starkenburg, January 25, 1894, vol I, p. 392,in  Marx Engels, Selected Works).” [Paul N. Siegel, Introduction] [in Leon Trotsky, Art and Revolution. Writings on Literature, Politics and Culture, 2009]