How does a rational mind attain truth? This is the central question addressed by Piaget in Sociological Studies. It concerns the developmental mechanism which makes possible both the acquisition of available knowledge and the creation of novel knowledge. Social orthodoxy, the rigid conformity of closed societies, ideological fervour and the power of tradition are familiar social phenomena. But none provides a guarantee of truth. Piaget's question, then, concerns how the developing mind comes to understand that some available beliefs are true rather than false, and how one generation comes to replace false values by true values. There is a widely held belief that Piaget's work offers, at best, an incomplete account of the social basis for the formation of knowledge. Sociological Studies shows that this is untrue and reveals how Piaget examines the extent to which psycho-social experience contributes to the development of rationality. In this first English translation, an international team of Piagetian scholars has ensured that this important text is available for wider analysis. Sociological Studies highlights the continuing relevance of Piaget's work today.