The theory of historical materialism is the core commitment of Marx’s social theory. More than his views on markets, philosophical methods, the state and social institutions, it is this theory which sets Marx’s views apart from alternative traditions in political philosophy. Marx believes that there is a tendency for societies to make moral and material progress. The point of Marx’s theory of historical materialism is to offer a theory of the mechanisms which produce this tendency. However, in Marx’s own formulation, (...) the precise nature of these mechanisms remains obscure. In The German Ideology, Marx emphasizes the growth of human productive powers as the fundamental cause of historical change and progress: social forms change in order to adapt to the requirements of further productive development. By contrast, in The Communist Manifesto and the Grundrisse, Marx emphasizes the desires and interests of classes as fundamental to explaining social change. Here, it is class struggles which determine not only when an old social form will be replaced by a new one, but also the nature of the new social form itself. Marx never specifies the connection between these two explanations of historical change, between the development of human productive powers and class struggles. In particular, Marx is not explicit as to whether there are two distinct mechanisms at work in the production of historical progress, or only one. (shrink)