All schizophrenia patients are mad, and none are sane. Their behaviour is incomprehensible. It tells us nothing about what they do in the rest of their lives, gives no insight into the human condition and has no lesson for sane people except how sane they are. There's nothing profound about it. Schizophrenics aren't clever or wise or witty — they may make some very odd remarks but that's because they're mad, and there's nothing to be got out of what they say. When they laugh at things the rest of us don't think are funny, like the death of a parent, they're not being penetrating, and on other occasions they're not wryly amused at the simplicity and stupidity of the psychiatrist, however well justified that might be in many cases. They're laughing because they're mad, too mad to be able to tell what's funny any more. The rewards for being sane may not be very many but knowing what's funny is one of them. And that's an end of the matter.
Kingsley Amis, Stanley and the Women, p. 147.