Can you solve the famously difficult green-eyed logic puzzle? - Alex Gendler
video description
You know that at least one person has green eyes, you know that person B knows one person has green eyes, but you DONT know that person B's knows that person C knows that one person has green eyes.
But this falls apart with a fourth person, because you do know that person B knows that person C knows one person has green eyes, because that one person is definitely person D. I think you have to tell them that n-1 people have green eyes, so that they can deduce that in two days everyone who sees a brown eyed person will have left, and on day three they can deduce that since everyone stayed, everyone has green eyes.
Date: 2020-08-22
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Comments and reviews: 9
Mad
This was poorly explained.
Firstly, because it's too short and leaps over some details that are crucial to really understand this difficult puzzle.
And secondly, because Mr. Gendler fails to establish that they would all have to know they are perfect logicians, which makes a huge difference.
This puzzle requires perfect logic AND perfect confidence in others' logic.
The prisoner being able to make the right inference about his eye color depends on him trusting the reasoning ability of the prisoner before him, and he depends in turn on his trusting the prisoner before him.
One of them could say I don't know if my eyes are green, not because he lacked the capacity to make the right inference, but doubted the capacity of the prisoner before him. So the logical approach not only requires each prisoner to be a perfect reasoner, but also requires each prisoner to assume that others are too.
Perhaps it would make more sense if the puzzle was about androids or robots of some kind.
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This was poorly explained.
Firstly, because it's too short and leaps over some details that are crucial to really understand this difficult puzzle.
And secondly, because Mr. Gendler fails to establish that they would all have to know they are perfect logicians, which makes a huge difference.
This puzzle requires perfect logic AND perfect confidence in others' logic.
The prisoner being able to make the right inference about his eye color depends on him trusting the reasoning ability of the prisoner before him, and he depends in turn on his trusting the prisoner before him.
One of them could say I don't know if my eyes are green, not because he lacked the capacity to make the right inference, but doubted the capacity of the prisoner before him. So the logical approach not only requires each prisoner to be a perfect reasoner, but also requires each prisoner to assume that others are too.
Perhaps it would make more sense if the puzzle was about androids or robots of some kind.
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IPere54
I don't know if I'm missing something but I think its wrong, if not tell me what is it, the video solution works for 2 people but not for more than that.
For example if we are 3 and I'm seeing two people with green eyes, I know that eachone of them is seeing atleast one person with green eyes and as the statement says At least one of you has green eyes I know that even if I don't have green eyes they are already seeing someone with green eyes so they won't ever be sured and I will never get the clue of they not leaving.
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I don't know if I'm missing something but I think its wrong, if not tell me what is it, the video solution works for 2 people but not for more than that.
For example if we are 3 and I'm seeing two people with green eyes, I know that eachone of them is seeing atleast one person with green eyes and as the statement says At least one of you has green eyes I know that even if I don't have green eyes they are already seeing someone with green eyes so they won't ever be sured and I will never get the clue of they not leaving.
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Sofia
Huh? If you say at least one of you has green eyes and you look around and theres 99 others with green eyes, that doesnt guarantee that you have green eyes too. It just means that a lot of people have green eyes. This only works when its two people, since the other person assumes youre the one with the green eyes. You cant do that when theres 99 others involved, if theres only a single guaranteed case of green eyes.
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Huh? If you say at least one of you has green eyes and you look around and theres 99 others with green eyes, that doesnt guarantee that you have green eyes too. It just means that a lot of people have green eyes. This only works when its two people, since the other person assumes youre the one with the green eyes. You cant do that when theres 99 others involved, if theres only a single guaranteed case of green eyes.
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Jayden
I mean if i see that there are 99 other people with green eyes, then very likely I would too.
And even if i was the unlucky 1 person without green eyes, my fate being stuck on that island was already in place so dying wouldnt mean much anyways because was i really living life in the first place? and the only way to break it was through that trial so why not give it a go
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I mean if i see that there are 99 other people with green eyes, then very likely I would too.
And even if i was the unlucky 1 person without green eyes, my fate being stuck on that island was already in place so dying wouldnt mean much anyways because was i really living life in the first place? and the only way to break it was through that trial so why not give it a go
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Naytte
I considered the solution mentioned in the video (I paused and thought for a bit) but I dismissed it as new information as the prisoners have no idea that one of them has green eyes. Telling them that one of them has green eyes, when no one of them knows it, is new information, isn't it? So I guess I'm kind of confused about what exactly new information means.
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I considered the solution mentioned in the video (I paused and thought for a bit) but I dismissed it as new information as the prisoners have no idea that one of them has green eyes. Telling them that one of them has green eyes, when no one of them knows it, is new information, isn't it? So I guess I'm kind of confused about what exactly new information means.
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Arjun
but in the example of adria and bill, they saw that others eyes were green so they will make sure that their eyes are not green individually, how can they think that as she or he didnt left and so my eyes are green
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but in the example of adria and bill, they saw that others eyes were green so they will make sure that their eyes are not green individually, how can they think that as she or he didnt left and so my eyes are green
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Remas
i would've said that they all have the same eye color. Therefore, they would look at each other, spot the green eyes, and instantly assume that they have green eyes too.
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i would've said that they all have the same eye color. Therefore, they would look at each other, spot the green eyes, and instantly assume that they have green eyes too.
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Kittykat_
Ima just assume I have green evens since I was there when I was born so my parents should have been there too since childbirth soooooo ye
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Ima just assume I have green evens since I was there when I was born so my parents should have been there too since childbirth soooooo ye
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Eriq
I'm going to break the rules of the puzzle to solve it because I'm so clever and funny - all the comments on these videos
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I'm going to break the rules of the puzzle to solve it because I'm so clever and funny - all the comments on these videos
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