Can you solve the famously difficult green-eyed logic puzzle? - Alex Gendler

One hundred green-eyed logicians have been imprisoned on an island by a mad dictator. Their only hope for freedom lies in the answer to one famously difficult logic puzzle. Can you solve it? Alex Gendler walks us through this green-eyed riddle.

Lesson by Alex Gendler, animation by Artrake Studio.

[avadadah]

"There were no reflective surfaces"
*shows image of mad dictator with reflective sunglasses*

[samwise]

Dictator: What is your statement?
Me: THE DICTATOR HAS REFLECTIVE SUNGLASSES

[x-tremefactory]

Imagine being the only one without green eyes and on the 99th day everyone just leaves 💀

[oatmeallover]

My brain understands this for about .2 seconds before getting confused again. It’s like trying to remember a dream

[asjakresevljakovic]

Too much information for my 3 brain cells

[qwerty-yehu]

or just be like "lmao why y'all haven't left yet"

[nikhilgarg]

Adria: Do you have green eyes?
Bill: Ozo.

[erikthehalfabee]

The original situation on the island is still weird to me. Every prisoner will see 99 pairs of green eyes at the meeting every day. But he/she might be the only blue-eyed prisoner. Nobody leaves, wouldn't you conclude most likely all 100 are green-eyed?

[Imamotherfreakingavocado]

Imagine Adria didn't have green eyes and Bill just wanted to watch the world burn.

[kirbycreep]

"Perfectly logical"
Yet no one tries to spill the water somewhere to see their reflection

[puzzLEGO]

For people still confused about how they got new information without you directly telling them new information, it’s because you say it to everyone collectively, effectively meaning everyone knows that everyone else knows that at least one person has green eyes. If you told them each separately without them knowing that everyone else was told the same information, they wouldn’t be able to escape. Once they all collectively know this, they all have that chain of hypothetical scenarios which goes until everyone except one person has red eyes. That one person with green eyes would leave on day one, but they don’t. Now you can see how they are able to communicate by either "leaving" or "not leaving". If we go back to the three-person example, if they knew everyone else's eye colour, but weren't allowed to know how many people were there on the following days, it would actually be impossible for them to all escape on the 4th day. Person A would only get as far as thinking "if I had red eyes they would leave on day 2" without actually being able to tell, because he wouldn’t know if they left or not on day 2.

[ahhhhhhhhhhhhsocool]

its amazing how the dictator made 100 perfect logicians without being one

[silverfish]

The Dictator's glasses = reflective surface

[ariella]

Honestly, if everyone around me had green eyes I wouldn't even think of the fact that another eye color could exist.

Edit: I'm going to stop responding to comments now, you all bring up valid points, but this wasn't meant to be a super well thought out comment lol

[nerox]

0:42 "There are no reflective surfaces"
The toilet in the back: Am i a joke to you

[Urmom-yxld]

Has anybody realized at 3:28, there are 101 people if you’d count up everybody shown on the screen?

[justinvanilla]

Meh, if I saw 99 other kids with green eyes Id also assume I have green eyes

[wacka.]

I would have said "If I were you, I would leave tonight"

[a_disgruntled_snail]

These logic puzzles are always so ridiculously contrived.

[photon]

So nobody tried pointing at their eyes, then the grass? Or something green at least.