One day the teacher walks into her classroom and notices that someone has written the word P*NIS in tiny letters on the blackboard. She scans the class looking for a guilty face. Finding none, she erases the obscenity and begins class. The next day, the word P*NIS is written on the board again, this time in bigger letters stretching about halfway across the board. Again, the teacher looks around in vain for the culprit, erases the graffito and proceeds with the day’s lesson. Every morning for nearly a week the trend continues, and each day the word appears in larger letters. Each day she rubs them out vigorously. At the end of the week, the teacher walks in expecting to be greeted yet again by the offending word. Instead, she finds this: “The more you rub it, the bigger it gets.”