Although current interpretations of Vygotsky's theory largely assume that instruction pushes development, the issue of how this occurs has yet to be clarified. For example, the notion of "zone of proximal development" has aroused strong disagreement, and the common conceptualization of the notion of "nonspontaneous concept" has been widely recognized as unsatisfactory. This article proposes a new interpretation of Vygotsky's theory of cultural development, closely based on Vygotsky's writings, that clarifies why and how instruction pushes development and resignifies the notions of zone of proximal development and nonspontaneous concept. The article introduces important nuances into the widely held interpretations of Vygotsky's theory and discusses some of the implications of these nuances for research and practice in educational psychology.