The classical Marxist view of history. It is described by Engels in the introduction to Socialism: Utopian and Scientific as seeking ‘the ultimate cause and the great moving power of all important historic events in the economic development of society, in the changes in the modes of production and exchange, in the consequent division of society into distinct classes, and in the struggle of these classes against one another’. Historical materialism is described by Marx and Engels as a scientific, empirical hypothesis, but in fact is a framework or guide for historical explanation, and as such measured more by the unifying insights it gives and the success of the research programme it generates. According to historical materialism, changes in the productive forces of a society lead to social conflict, and the specific forms of social organization that emerge reflect the underlying structure of the means of production (see base and superstructure). One of the main problems in understanding Marxism is to relate historical materialism to historicism, or the idea that history takes a determined, inevitable shape, with movements and aims that are not in accord with that shape being doomed in advance to failure. In principle historical materialism has no such implication, and Marx himself took care to distance it from any fatalistic interpretation.