1.whats meaning of and gist of this words"single thing.""knock out a single thing"
2.and meaning of"but nothing else"
SACKS: Well, as a physician or scientist interested in the nervous system
and in patients, I learn by seeing what happens when things go wrong.
It’s very difficult to learn when everything goes right. You think, for
example, the whole world, full of color, and movement, and depth, and
meaning, is given to you. But it’s not. It is dependent on the goodwill
and the good functioning of forty or fifty different parts of the brain, all
linked together. And any one of these can go wrong and knock out a
single thing, like knocking out color but nothing else.