It is said that the famous
logician Bertrand Russell was once trying to get this very point across at a
public lecture when a
heckler interrupted him. "So prove to me that if two plus two is five,
I'm the Pope," the
heckler said.
Russell who was apparently very good at thinking on his feet replied: "
Very well, from 'two plus two equals five' it follows, subtracting three from each side, that two equals one. You and the Pope are two, therefore you are one."