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 provide 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. Piaget's work includes an account of the psycho-social origins of intellectual development but his constructivist commitments require all specific forms of experience to be legitimated in relation to norms of rationality. In particular, Piaget's account is concerned less with questions about the initial origins of knowledge than with the acquisition, construction and integration of rational norms. In this first English translation of Sociological Studies , an international team of Piaget scholars has ensured that this important text is available for wider analysis. With a new introduction by Leslie Smith, Sociological Studies hightlights the continuing relevance of Piaget's work.