This paper is concerned with Piaget’s theory of cognitive development in infancy. It is argued that Piaget generalizes from a Cartesian epistemology and thus views the infant as interacting with a material world, but without regard to the significance of communication with others. Drawing on Piaget’s own work and some contemporary studies of social interaction it is concluded that one may reinterpret Piaget’s descriptive psychology in terms of the infant’s growing communicative competency. Such reinterpretation is consistent with some recent epistemologies.