The Unexpected Hanging
A murderer had been found guilty of a particularly heinous crime. The judge sentencing the murderer decides that death is too good for him; he wants to make him suffer. He passes his sentence, “You will be taken from this place, and hanged from the neck until you are dead. Before that, though, you will suffer anguish, waiting, never knowing whether this will be the day that you will die. One morning, sometime in the next week, it will happen, but until it does you will live in fear.”
The murderer leaves the courtroom with a light heart, knowing that the sentence handed down to him cannot be carried out.
He reasons like this:
Suppose that on the seventh morning I am alive. I will know that that is the day that I am to die. But the judge said that I would not know the day that I am to die. Therefore I will not be hanged on the seventh day. The sixth day is the last day that it could be.
But in that case, if I am alive on the sixth morning then I will know that it is the sixth day on which I am to be hanged. But the judge said that I would not know the day that I am to die. Therefore I will not be hanged on the sixth day.
He continues, applying the same reasoning to the fifth day, and then to the fourth, and so on, concluding that he cannot be hanged on any day according to the judge’s instructions. The sentence handed down to him cannot be carried out.
He is hanged on the morning of the third day, much to his surprise.