The various contributions to this volume converge on two themes. First, the explanatory role of social interaction, which, for a long time, has been a source of criticism of Piaget’s view of intelligence, is dealt with not only in relation to cognitive development, but also to language acquisition and to education. The second point of thematic convergence is the compatibility of genetic epistemology and psychoanalytic theory in view of the establishment of relationships between emotional and cognitive development.