single thing
hi there
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.

Question

single thing
hi there
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.

Answer

In this particular context, 1- means that there are lots of parts of the brain all working together, but if something goes wrong then a "single thing" in this example color, is lost or "knocked out". Think of it like a chain of dominoes, one domino is a single thing (a single domino), the brain functions are the falling dominoes and if something bad happens then you will lose one domino (it is "knocked out")
2- here, this is another way of saying that only one thing is affected. In the example- only color is affected, but nothing else refers to the "movement, and depth, and meaning" which is not affected.

I hope this helps? because of the scientific context it can sometimes change the meaning of certain phrases such as the ones you pointed out.

Answer

???