Realists such as Waltz have argued that members of the proletariat
concluded during the First World War that they had more in common
with their own national bourgeoisie than with the working classes of
other countries. The argument was that no-one with a good understanding
of nationalism, the state and war should have been even mildly
surprised by this turn of events, yet many socialists were dismayed
by the actions of the European proletariat. For realists, the failure to
anticipate this outcome demonstrates the central flaw in Marxism – its
economic reductionism, as manifested in the belief that understanding
capitalism would explain the mysteries of the modern world and its
unprecedented political opportunities (Waltz 1959: Chapter 5). This is
one of the most famous criticisms of Marxism within the study of international
relations. There are three points to make about it.