In a book with far-reaching implications, Edward S. Klima and Ursula Bellugi present a full exploration of a language in another mode—a language of the hands and of the eyes. They discuss the origin and development of American Sign Language, the internal structure of its basic units, the grammatical processes it employs, and its heightened use in poetry and wit. The authors draw on research, much of it by and with deaf people, to answer the crucial question of what is fundamental to language as language and what is determined by the mode (vocal or gestural) in which a language is produced.