Once there was an emperor who was very evil and very fierce. He said 2 + 2 = 6. All the people were afraid of him and therefore agreed that 2 + 2 = 6.

When the emperor died the next emperor was less evil and less fierce. He said 2 + 2 = 5. All the people asked themselves, "How could we have been so stupid as to believe that 2 + 2 = 6?"

A young mathematician thought for a long time and he concluded that 2 + 2 = 4. He wrote a book to prove his theory. He decided to take it to the publisher, but on the way, two strangers approached him. "Comrade," they asked, "what are you doing? Do you really want to go back to the days when 2 and 2 were 6?"

This story is found in Marx, Money and Mysticism After Mao.