Activity theory is an interdisciplinary approach to human sciences that originates in the cultural-historical psychology school, initiated by Vygotsky, Leont'ev, and Luria. It takes the object-oriented, artifact-mediated collective activity system as its unit of analysis, thus bridging the gulf between the individual subject and the societal structure. This volume is the first comprehensive presentation of contemporary work in activity theory, with 26 original chapters by authors from ten countries. In Part I of the book, central theoretical issues are discussed from different points of view. Some topics addressed in this part are epistemology, methodology, and the relationship between biological and cultural factors. Part II is devoted to the acquisition and development of language - a theme that played a central role in the work of Vygotsky and Luria. This part includes a chapter that analyzes writing activity in Japanese classrooms, and an original case study of literacy skills of a man with cerebral palsy. Part III contains chapters on play, learning, and education, and part IV addresses the meaning of new technology and the development of work activities. The final part covers issues of therapy and addiction.