Aleteia

Can you solve the “three gods” riddle?

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TED-Ed tries to grow our minds with an exercise in logic.

TED is an organization that strongly believes the free exchange of ideas has the power to change attitudes, lives, and the world. TED was founded in 1984, but they became incredibly popular after distributing their TED-Talks online. Now, they have begun a new series of videos called TED-Ed, which celebrates the ideas of teachers and is more geared towards students.

In this TED-Ed video we are challenged to solve the “three gods” riddle, credited to American mathmatician and logician Raymond Smullyan (who died just this year at the age of 97). It was popularized when his colleague, George Boolos, published it in The Harvard Review of Philosophy, in 1996.

The original riddle is stated as follows:

Three gods, A, B, and C, are called, in no particular order, True, False, and Random. True always speaks truly, False always speaks falsely, but whether Random speaks truly or falsely is a completely random matter. Your task is to determine the identities of A, B, and C by asking three yes-no questions; each question must be put to exactly one god. The gods understand English, but will answer all questions in their own language, in which the words for yes and no are da and ja, in some order. You do not know which word means which.

TED-Ed changed the term gods to alien overlords, a decision which may have been for the benefit of the animated video as much as it was to assuage religious criticism, and they changed the names of the aliens from A, B, and C to Tee, Eff, and Arr.

Regardless of these little changes, the riddle still stands as an excellent exercise in logic and problem solving. While the answer is provided at the end of the video, we encourage you to gather the best minds in your family and see if you can figure it out!