The World's Hardest Logic Puzzle Ever!

Complete this exercise, which will give you an opportunity to solve a difficult logic puzzle. Watch the video on this puzzle for a discussion of the solution.

This is not really a tutorial, but an exceedingly hard logic puzzle for you to solve. According to the late philosopher and logician George Boolos, who was a great teacher and logician at MIT, the hardest (recreational) logical puzzle is one that was invented by the logician and puzzle-master Raymond Smullyan, and modified slightly by the computer scientist John McCarthy.

Here is the puzzle:


Here is the TED-Ed video on this puzzle, with a discussion of the solution:

Source: Joe Lau and Jonathan Chan,
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Last modified: Tuesday, September 10, 2019, 5:57 PM