A milestone of child psychology, _The Child's Conception of the World_ explores the ways in which the reasoning powers of young children differ from those of adults. What conceptions of the world does the child naturally form at the different stages of its development? To what extent does the child distinguish the external world from an internal or subjective world and what limits does he or she draw between the self and objective reality? These questions make up the first problem, the child's notion of reality. A second fundamental problem is the significance of explanations put forward by the child. What use does he or she make of the notions of cause and of law? Is the form of explanation presented by the child a new type? These and like questions form the second problem, the child's notion of causality.