This John lives his life with figures and he is afraid to fly. One day his friend, Bill, asks him why you have this irrational fear of flying.
"Revolutionary?" John responds, "Not at all. I've only calculated the barriers of the bomb kept on the plane, and it's too much for my comfort."
A few days later, Bill just climbed a flight so that John sat next to him in the seat.
"What happened? What obstacles have changed?"
"No," John answered. "Obstacles of an aircraft bombing have not changed, but I calculated the inequality of two bombs on the plane, and I found those obstacles more acceptable, so now I bring my own."