Many discussions of the difference between Vygotsky and Piaget focus on the proximal locus of development. For Piaget it is said to be in individual children, who construct knowledge through their actions on the world; for Vygotsky it is said to be in social processes. A more appropriate way to distinguish between them has to do with the role attributed to cultural mediation. Mediation of human action by cultural artifacts played a central role in Vygotsky’s account of human development, but was much less important for Piaget. Claims regarding the social origins of individual mental processes in Vygotsky’s account need to be understood in light of his claims regarding how artifacts mediate social and individual functioning.