When my information changes, I alter my conclusions. What do you do, sir?

John Maynard Keynes (1883-1946) English economist
(Attributed)

Reply to a criticism of having changed his position on monetary policy. Quoted in Paul Samuelson, "The Keynes Centenary" The Economist, Vol. 287 (1983), but possibly apocryphal (see here).

Variants:
  • "When events change, I change my mind. What do you do?"
  • "When the facts change, I change my mind. What do you do, sir?"
  • "When someone persuades me that I am wrong, I change my mind. What do you do?"