Boileau said that Kings, Gods and Heroes only were fit subjects for literature. The writer can only write about what he admires. Present-day kings aren't very inspiring, the gods are on a vacation and about the only heroes left are the scientists and the poor … And since our race admires gallantry, the writer will deal with it where he finds it. He finds it in the struggling poor now.

Radio interview (1939) quoted in Introduction by Robert DeMott to a 1992 edition of The Grapes of Wrath