To reason is to talk. To think is to use tools. To learn is to join a community of practice. This book explores thought and reasoning as inherently social practices, as actions situated in specific environments of demand, opportunity, and accountability. Authors from diverse disciplines - psychology, sociology, artificial intelligence, linguistics, anthropology - examine how people think and learn in settings as diverse as a factory, a classroom or an airplane cockpit. The tools that people use in these varied settings are both physical technologies and cultural constructions: concepts, structures of reasoning, and forms of discourse. This volume in the NATO Special Programme on Advanced Educational Technology is based on an international conference on situated cognition and learning technologies.