I own any form of humor shows fear and inferiority. Irony is simply a kind of guardedness. So is a twinkle. It keeps the reader from criticism. Whittier, when he shows any style at all is probably a greater person than Longfellow as he is lifted priestlike above consideration of the scornful. Belief is better than anything else, and it is best when rapt, above paying its respects to anybody's doubt whatsoever. At bottom the world isn't a joke. We only joke about it to avoid an issue with someone to let someone know that we know he's there with his questions: to disarm him by seeming to have heard and done justice to this side of the standing argument. Humor is the most engaging cowardice.

Letter to Louis Untermeyer (10 March 1924).