This article treats Stalin's contributions todialectical and historical materialism. It argues that the latterfound his theses of the `enormous' role of ideas, and of theexistence of social phenomena that do not belong either to thebasis or to the superstructure, in Georgij Plekhanov's `monism'.Nevertheless, Stalin did add some new points of his own.Furthermore, his adopting Plekhanov's monism also helps usunderstand the apparent contradiction between Stalin's emphasison non-economic and non-class factors in human history and hisrejection of `idealist' rudiments in dialectics.