Seven monks are living in a monastery. They have taken a vow of silence, and cannot communicate with each other in any way. Each morning, the monks silently enter a large meditation chamber, where they all sit silently facing each other to meditate, then return to their own rooms at night. They are expected to meditate every day, but if they ever become aware that they have reached enlightenment, they will pack up their belongings in the night and leave the monastery. When a monk reaches enlightenment, a dark mark appears on his forehead. There are no mirrors in the monastery, so each monk cannot see his own forehead, though he *can* see the foreheads of all of the other monks when they are all in the meditation chamber together. One night, while all the monks are in their own rooms, a booming voice rings out: "At least one of you has reached enlightenment!" Will any of the monks leave the monastery? When?