Three patients in a mental institution prepare for an examination given by the psychiatrist. If they pass the examination, they will be free to leave the hospital. However, if they fail, they will be detained for five years. The doctor takes them to the diving board looking over an empty swimming pool, and asks the first patient to jump. The first patient jumps and breaks both arms. Then the second patient jumps and breaks both legs. The third patient looks over the side and refuses to jump. "Congratulations! You're a free man now. Just tell me why didn't you jump?" asks the doctor. To which the third patient answers, "Well Doctor, I can't swim!"