Reflecting the focus of a Jean Piaget Symposium entitled Biology and Knowledge: Structural Constraints on Development, this volume presents many of the emergent themes discussed.Among these themes are:Structural constraints on cognitive development and learning come in many shapes and forms and involve appeal to more than one level of analysis.To postulate innate knowledge is not to deny that humans can acquire new concepts.It is unlikely that there is only one learning mechanism, even if one prefers to work with general as opposed to domain-specific mechanisms.The problems of induction with respect to concept acquisition are even harder than originally thought.