Since it was introduced to the English-speaking world in 1962, Lev Vygotsky'sThought and Language has become recognized as a classic foundational work ofcognitive science. Its 1962 English translation must certainly be considered one of the mostimportant and influential books ever published by the MIT Press. In this highly original explorationof human mental development, Vygotsky analyzes the relationship between words and consciousness,arguing that speech is social in its origins and that only as children develop does it becomeinternalized verbal thought. In 1986, the MIT Press published a new edition of the originaltranslation by Eugenia Hanfmann and Gertrude Vakar, edited by Vygotsky scholar Alex Kozulin, thatrestored the work's complete text and added materials to help readers better understand Vygotsky'sthought. Kozulin also contributed an introductory essay that offered new insight into Vygotsky'slife, intellectual milieu, and research methods. This expanded edition offers Vygotsky's text,Kozulin's essay, a subject index, and a new foreword by Kozulin that maps the ever-growing influenceof Vygotsky's ideas.