A crocodile snatched her child from a mother and asked her to guess whether it would eat the child, on the condition that if it guessed correctly, it would return the child; If she guesses wrong, it will eat the child. Mother replied, "You will eat my child."

the result is

If the mother guessed correctly, according to the agreement, the crocodile should be returned to the child; But in this way, the mother guessed wrong. According to the agreement, the crocodile should eat the child.

If the mother guessed wrong, according to the agreement, the crocodile should eat the child; But in this way, the mother guessed right. According to the agreement, the crocodile should be returned to the child.

So crocodiles should eat children, if and only if crocodiles should be returned to children. In any case, crocodiles cannot carry out their agreements.

Some simple contradictions are different from the actual ideas. This estimate shows that the crocodile's actual idea is to eat the child, but in fact, the mother guessed right and let the child go. )