The human story does not always unfold like a mathematical calculation on the principle that two and two make four.  Sometimes in life they make five or minus three; and sometimes the blackboard topples down in the middle of the sum and leaves the class in disorder and the pedagogue with a black eye.  ~Winston Churchill, quoted in F.B. Czarnomski, The Wisdom of Winston Churchill, p59, speech, London, 7 May 1946HM