Madness is terrific I can assure you, and not to be sniffed at; and in its lava I still find most of the things I write about. It shoots out of one everything shaped, final, not in mere driblets, as sanity does.
If a writer stops observing he is finished. But he does not have to observe consciously nor think how it will be useful. Perhaps that would be true at the beginning. But later everything he sees goes into the great reserve of things he knows or has seen.