Fascinating, and it changed the way I thought about deaf people. Sacks shows that Sign language is as full and complete a language as English, French, or Chinese, and that the Deaf are in some ways as much like an independant cultural minority than as just individual people with a disability. He shows how devastating it can be to be born deaf (as opposed to losing hearing later in life), more so even than being born blind, because it can cut you off from meaningful communication with parents, and from learning any language at all. And if you don't have a language, how can you think about anything that isn't immediate and concrete?