A man always has two reasons for what he does — a good one, and the real one.

John Pierpont "J. P." Morgan (1837-1913) American banker and financier
(Attributed)

Quoted in Owen Wister, Roosevelt: The Story of a Friendship, p. 280 (1930). There's no record in Morgan's writings, and versions of the quote from others can be found in the early 1800s. See here for more details.

Sometimes given as "A man generally has two reasons for doing a thing: one that sounds good, and a real one."