These days, if you talk about an autistic child, he differs from “typical” children, while a dwarf differs from “average” people. You are never to use the word normal, and you are certainly never to use the word abnormal. In the vast literature about disability rights, scholars stress the separation between impairment, the organic consequence of a condition, and disability, the result of social context. Being unable to move your legs, for example, is an impairment, but being unable to enter the public library is a disability.
