Logical inversion

From A Treasury of Jewish Folklore by Nathan Ausubel.

The Rabbi and the Inquisitor

The city of Seville was seething with excitement. A Christian boy had been found dead, and the Jews were falsely accused by their enemies of having murdered him in order to use his blood ritually in the baking of matzos for Passover. So the rabbi was brought before the Grand Inquisitor to stand trial as head of the Jewish community.

The Grand Inquisitor hated the rabbi, but, despite all his efforts to prove that the crime had been committed by the Jews, the rabbi succeeded in disproving the charge. Seeing that he had been bested in argument, the Inquisitor turned his eyes piously to Heaven and said:

“We will leave the judgment of this matter to God. Let there be a drawing of lots. I shall deposit two pieces of paper in a box. On one I shall write the word ‘guilty — the other will have no writing on it. If the Jew draws the first, it will be a sign from Heaven that the Jews are guilty, and we’ll have him burned at the stake. If he draws the second, on which there is no writing, it will be divine proof of the Jews’ innocence, so we’ll let him go.”

Now the Grand Inquisitor was a cunning fellow. He was anxious to burn the Jew, and since he knew that no one would ever find out about it, he decided to write the word “guilty” on both pieces of paper. The rabbi suspected he was going to do just this. Therefore, when he put his hand into the box and drew forth a piece of paper he quickly put it into his mouth and swallowed it.

“What is the meaning of this, Jew?” raged the Inquisitor. “How do you expect us to know which paper you drew now that you’ve swallowed it?”

“Very simple,” replied the rabbi. “You have only to look at the paper in the box.”

So they took out the piece of paper still in the box.

“There!” cried the rabbi triumphantly. “This paper says ‘guilty,’ therefore the one I swallowed must have been blank. Now, you must release me!”

And they had to let him go.