An Irresistible Cannonball

I gave the following puzzle from Raymond Smullyan’s book What is the Name of this Book? to my AMSA students.

What happens if an irresistible cannonball hits an immovable post?

This puzzle is known as the Irresistible Force Paradox. The standard answer is that the given conditions are contradictory and the two objects cannot exist at the same time.

My AMSA student gave me a much cuter answer: The post falls in love with the cannonball as it is so irresistible.



  1. Sean:

    Superman was asked this question in the comic “All-Star Superman” several years ago. His answer was “They surrender.”

  2. Dan:

    But the post can’t (be moved to) fall in love.

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