Jean Stein vanden Heuvel interviews William Faulkner in 1956 in the Paris Review:
Do you mean the writer should be completely ruthless?
The writer's only responsibility is to his art. He will be completely ruthless if he is a good one. He has a dream. It anguishes him so much he must get rid of it. He has no peace until then. Everything goes by the board: honor, pride, decency, security, happiness, all, to get the book written. If a writer has to rob his mother, he will not hesitate; the “Ode on a Grecian Urn” is worth any number of old ladies.
INTERVIEWER
Then could the lack of security, happiness, honor, be an important factor in the artist's creativity?
FAULKNER
No. They are important only to his peace and contentment, and art has no concern with peace and contentment.
More here. [Thanks to John Ballard.]