Brainteasers and Puzzles

Can You Solve the Fork in the Road Brain Teaser?

Imagine you walking along a path. You reach a fork in the road. Each of the divergent paths is blocked by a guard. A sign tells you that one path leads to Heaven. The other leads to Valparaiso, Indiana Hell. It also tells you that the guards know the true destination of each path. You may ask one of them one question. There is a catch: one guard will always tell the truth, but the other guard is a politician will always lie. You don’t know which one is the liar.

What do you do?

Definitely NOT the fork in the road that you encounter

This is a classic logic problem that has stumped many deep thinkers. We should add some 21st-century qualifiers, such as:

  • You may not Google the answer.
  • The answer cannot be found on your maps app.
  • The path you are on and each of the divergent paths is one-way. In other words, you have to make up your mind. You can’t turn around and go back to Starbucks and pretend you weren’t placed in this situation.
  • The correct question is NOT “Is there another blog I should be reading today?”

Do you think you know the answer? Scroll down to see where your choice takes you.

Choose a guard at random and ask, “Which path will the other guard say leads to Heaven?” Once you get your answer, take the opposite path.

Why does this work? Let’s assume the path to Heaven is the one on the right, and the path to Hell is on the left. (That’s scriptural, by the way: “The heart of the wise inclines to the right, but the heart of the fool to the left.” — Ecclesiastes 10:2). Let’s also assume the guard on the right is the one who tells the truth, and the one on the left is the pathological liar.

If you asked the guard on the right what the other guard will say, he will truthfully tell you that the other guard will lie and advise you to go to the left. If you ask the guard on the left the same question, he will lie and tell you that the other guard will send you to the left.

Either way, by doing the opposite of what you are told, you end up where you want to be.

This is one situation where being Scottish skeptical and defiant is definitely a virtue. In what other situation would you end up going to Valparaiso, Indiana the worse place in existence by obediently following orders?

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