The assumption that the past is an infinite and plastic symbolic resource, wholly susceptible to contemporary purposes, is widespread in contemporary anthropology. It is partly rooted in Malinowski's conception of myth as social charter and partly in Durkheim's formulation concerning the cross-cultural relativity of fundamental categories of human thought. This article is a critique of this assumption, and suggests the existence of culturally variable sets of norms whose function is to regulate the inherent debatability of the past. Such norms, which vary substantively from culture to culture, are neverthless from a formal point of view subject to certain universal constraints. An example from south India is the bass for this argument, which also has implications for the theoretical analysis of social change.