One day, the director of a mental hospital tried to test the patients' conditions, see if they had become better. He had a door drawed on a wall, then told the patients: “If you can go out from this door, you can go home!”So the patients mostly flushed away toward the door on the wall. Only one  man didn't move at all, the leader thought he had become normal, so asked him: “Why don't you go?”This patient answered: “You are absolutely silly, I have the key, how can they open the door without it?”