Language [can] be expressed . ...

Language [can] be expressed . . . by movements of the hands and face just as well as by the small, sound-generating movements of the throat and mouth. Then the first criterion for language that I had learned as a student—it is spoken and heard—was wrong; and, more important, language did not depend on our ability to speak and hear but must be a more abstract capacity of the brain. It was the brain that had language, and if that capacity was blocked in one channel, it would emerge through another.
 Harlan Lane

Quotes from the same author

The interests of the deaf child and his parents may best be served by accepting that he is a deaf person, with an elaborate cultural and linguistic heritage that can enrich his parent's life as it will his own.
 Harlan Lane