The sociology of knowledge has been particularly fascinated by Marx´s twin concepts of “substructure/superstructure” (Unterbau/Ueberbau). It is here particularly that controversy has raged about the correct interpretation of Marx´s own thought. Later Marxism has tended to identify the “substructure” with economic structure tout court, of which the “superstructure” was then supposed to be a direct “reflection”. It is quite clear now that this misrepresents Marx thought, as the essentially mechanistic rather that dialectical character of this kind of economic determinism should make one suspect. What concerned Marx was that human thought is founded in human activity (“labour”, in the widest sense of the word) and in the social relations brought about by this activity. Substructure and superstructure as best understood if one views them as, respectively, human activity and the world produced by that activity. In any case, the fundamental “sub/superstructure” scheme has been taken over in various forms by the sociology of knowledge, beginning with Scheler, always with an understanding that there is some sort of relationship between thought and an “underlying” reality other than thought. The fascination of the scheme prevailed despite the fact that much of the sociology of knowledge was explicitly formulated in opposition to Marxim and that different positions have been taken within it regarding the nature of the relationships between the two components of the scheme.