The quest for certainty

Once, after McNamara had rattled off the odds for the success of various military operations -- 65 percent for this one, 30 for that -- [George] Ball had joked that perhaps the figures were actually 64 percent and 29 percent. He saw that such teasing did not amuse the defense secretary.

-- A. J. Langguth, Our Vietnam: The War 1954-1975 at 367.