The doctrine of historical materialism, given the two elements of economic articulation and class friction, becomes the key to understanding true revolutions; that is, those changes in the complex state of society from which innovations in law, new political directions and new moral dispositions have derived.

From Storia, filosofia della storia, sociologia e materialismo storico (“History, Philosophy of History, Sociology and Historical Materialism”), in Scritti varii: editi e inediti di filosofia e politica (“Various Writings: Published and Unpublished Works on Philosophy and Politics”), collected and published by Benedetto Croce, Giuseppe Laterza & Figli, Bari, 1906, chap. 5, p. 254.