The ethnography of lowland South American societies has occupied a central place in recent debates concerning what has been called the 'ontological turn' in anthropology. The concepts of 'animism' and 'perspectivism', which have been revigorated through studies of Amerindian ontologies, figure increasingly in the ethnographies of non-Amerindian peoples and in anthropological theory more generally. This article traces the theoretical and empirical background of these concepts, beginning with the influence of Lévi-Strauss's work on the anthropology of Philippe Descola and Eduardo Viveiros de Castro, and proceeding with their impact on Amazonian ethnography. It then investigates the problems that two alternative traditions—one combining a cognitivist with a pragmaticist approach, the other a phenomenological one—pose to recent studies of Amazonian ontologies that rely on the concepts of animism and perspectivism. The article concludes by considering how animism and perspectivism affect our descriptions of Amerindian society and politics, highlighting the new challenges that studies of Amerindian ontologies have begun to address.