Podcast Episode

Can you solve the troll’s paradox riddle? - Dan Finkel

TED-Ed
Oct 12, 20266 minEN

Who’s talking

7 speakers
Addison Anderson3 min · 61%
Paris Hilton28 sec · 9%
Speaker 728 sec · 8%
Speaker 827 sec · 8%
Speaker 121 sec · 6%
Speaker 615 sec · 5%
1 other7 sec · 2%

Transcript

8 turns · 6 min
Speaker 10:00

Flowing ad budget on metrics that look great till the CFO sees them, that's bull spend. And marketers are calling it out in Dashboard Confessions.

Speaker 20:09

I remember telling my boss, it'll be good for the brand, when leads were slow. Yeah, it wasn't.

Speaker 10:17

Cut the bull spend. LinkedIn lets you target by company, job title, and more. Advertise on LinkedIn. Spend $250 on your first campaign and get a $250 credit. Go to linkedin.com slash campaign. Terms and conditions apply.

PH
Paris Hilton0:30

College football is back, so Hilton called in me, the superstition concierge, to make your fan rituals a reality. Need a room to match your lucky number? We got you. Want to make sure our team doesn't wash your lucky jersey? Ooh, that smells lucky. Hilton's unmatched hospitality can keep up with any superstition. Even a marching band wake-up call at 555 in 55 seconds. Hit it! When you need a team that will do whatever it takes on game day, it matters where you stay. Hilton, for the stay.

AA
Addison Anderson1:08

You've discovered a doorway to another realm, and now you and your brother are off exploring the wonderful world of Paradoxica. Fantastically paradoxical creatures crawl, run, and fly around you. And then you see the troll. It's catching all the creatures in an enormous net. you bravely step forward and demand it let them go. The troll laughs. If you're such a fan of paradoxes, it says, then I'll make you an offer. If you say something true, I'll release all these creatures. You're about to say you are a troll, but before you can, the troll grabs your brother. If you say something false, he continues, then I'll release your brother. Your statement can only be a single sentence, and as you can see, I hate paradoxes more than anything. If you try to cheat by saying something paradoxical, like this statement is false, then I'll eat your brother and the creatures. What true-false statement can you say to force the troll to free your brother and the paradoxical creatures? This seems like an impossible situation, but incredibly, you can say something that will force the troll to release all its prisoners. The trick Smullyan came up with involves saying a statement whose truth or falseness depends on what you want the troll to do. Your statement still has to be carefully crafted. For example, if you were to say, you are going to free the creatures and my brother, the troll could respond, that's false, I'm only going to free your brother. Similarly, if you said you will free the paradoxes, the troll could say, that's true, and free the paradoxes. But watch what happens if you say, You will free my brother. The statement can't be false because if it were, the troll, by its own rules, would have to free your brother. That would make the statement paradoxically true and false. But the troll hates paradoxes and would never willingly create one. So his only option is for the statement to be true. If you will free my brother is true, then the troll has to release your brother. And by its own rules, the troll has to free the creatures as well, since you said a true statement. By wielding just five words like a logical scalpel, you've forced the troll to free all its prisoners. As the troll stomps off in anger, the

Episode notes

Practice more problem-solving at https://brilliant.org/TedEd/
Solution to bonus riddle: https://brilliant.org/TedEdTrollParadox/

Uploaded 20-12-18

You and your brother have discovered another realm and set off exploring the new wonderful world. Along the way, you see a troll catching creatures in an enormous net. The troll agrees to release the creatures if you can come up with a statement that is both truth and false. Can you come up with the correct sentence and force the troll to release them? Dan Finkel shows how.

Lesson by Dan Finkel, directed by Artrake Studio.

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