I've barely gotten through the opening so maybe you touch on this, but, nothing in the rules say you can't just speak with eachother? Why not have someone walk around and just tell everyone what eye color they have and have someone tell them what eye color they have so everyone's eye color is known?

Did we ever state that the islanders have perfect memory too? If not, I'm sure some would forget, Leading to a confusing situation where nobody's quite sure who has blue eyes and who knows it and some folks with brown eyes might even think they do.

Wait....can't everyone just tell the dude with blue eyes that he has blue eyes?

I figured out a very similar method to solve this... each person would count how many blue eyes they see, then wait that many days before leaving. This will result in all the blue eyes leaving on the same day, 1 day before the brown eyes. for instance, lets say you have a group of 5 people, 3 having blue eyes and the rest having brown eyes. each blue eyes person would see 2 people with blue eyes, and would wait 2 days before leaving. the brown eyes people would see 3 blue eyed people and would wait 3 days, only to not leave as they would see on the third day that all the blue eyed people left.

Yo this one is pretty cool at first I missed howd the browneyed people wouldnt start questioning their eye colour but theyre always waiting 1 day longer thus are safe

Day 1 X: Hey Chad, is the stranger telling the truth? Chad: Yeah. X: ....welp.

Isn’t this so horrifying?

what if I'm a perfect logician but really suck at counting?

I see one glaring problem. The brown-eyed folks have zero idea that they have brown eyes. If the blue-eyed people just collectively decide to disobey the rule of leaving at midnight, then everyone's going to be thrown off guard.

The stranger’s name? Seto Kaiba

My brains is exploding

How can the islanders be sure the stranger isn't lying?

How do they maintain 10 people with blue eyes?

3:30 but people with brown eyes would also think that they have blue eyes, cause they don't know their own eye's color, and they could think the same as the blue eye's people. Am i missing something there?

My guess before watching the explanation, if there’s one person with blue, he leaves that midnight, if there’s 2 people with blue eyes, neither will leave that midnight, then both will leave the next midnight, if there’s 3 or more, none of them will leave (I think) Edit: oh shit I thought I was smart for figuring out the 2 person case and assumed that was the end, I should have thought through the rest of the cases (still haven’t completed the 3 explanation yet) I guess that every increment of blue eyes person is another midnight that passes before they all leave

So wait i just realized its either they all leave the 1st day or only the blue eyed people leave the first day let me explain , if they are all at first under the impression they all have brown eyes if all the people are "perfect logicians" this includes brown eyed people, then if the person who comes to the island says they see a person with blue eyes with the rules at 0:46 this means that if they all know someone else has blue eyes but they didn't leave, then the brown eyed people will come to the exact same conclusion as the people with blue eyes (in this example there will be 4 people 2 brown eyed 2 blue eyed the scale doesn't matter they all think alike whether 100 or 1), so the person with brown eyes will also leave with them thinking "he said he saw someone has blue eyes here and its not me" but the next day no one leave so the person with brown eyes thinks oh so i must also have blue eyes if he didnt leave thinking me and the other guy were the only 2 dudes with blue eyes so us 3 have blue eyes, this is the exact same thought running through the other peoples heads as well. This isnt the case if the person says the exact amount of people so if he says for example there is 10 blue eyed people then the brown eyed people can see that there are infact only 10 people with blue eyes so they must have brown eyes. But if none of them are under the impression they have blue or brown eyes then same, result everyone will leave. EDIT/TLDR: Want to add that unless the place that take the people with blue eyes will not accept people with brown eyes at all then the brown eyed people will leave assuming they dont take themselves off the island alone, along with the fact that the brown eyed people cant communicate to eachother that the other person has brown eyes. And this video is a perspective from the blue eyed people but just think again to how you state the video but just imagine it as a brown eyed persons perspective and as you said in the 2 blue eyed people example "on day 1 you see 2 people with blue eyes" and then if those 2 dont leave then that means there's 3 which is you (even tho you have brown)

Ted-ed

0:20-030, what's missing is do the Islanders KNOW THAT ONLY TEN PEOPLE HAVE BLUE EYES? In that case yes, anyone with blue eyes will see 9 others with blue eyes and they'll all leave, all ten people. (Assuming there's no interaction and discussions amongst them that will leave only one behind)??

Too bad you still don't know what Ozo means...

wouldn't the brown-eyed ppl leave as well? (Edit : nevermind, they will count 1 more blue eyed person so their own exodus is delayed by 1 day and they'll cancel it when they see the blue eyed ppl gone on the day they leave) Also wouldn't they be able to make the fact that "someone has blue eyes" common knowledge by simply existing on an Island where you will necessarily know that there is either 9 or 10 of them depending on whether you're one of them or not? Do they really need the stranger to kickstart that exodus phenomenon?

Something that bother me is that one you saw 3 people with blue eye you dont need the stranger anymore because you know everyone have saw at least one , said or not

Ok. I get it.

in reality, the villagers have had strong bond with each other and would like everyone to continue live on the island. upon the stranger saying abt the uncommon eye color, the villagers kill the stranger. and later the rule changed into nobody talks abt eye colors or theyll die. so in the end no one left the island except, in the realisation that water can reflect their images like mirror

i don’t get it. to me it sounds like they’re reaching for conclusions that are only possible to be definitively made in a different mutually exclusive possibility. the chain breaks behind itself

So is the point of this logic problem that the brown eyed individuals would always wait one day beyond what the blue eye people wait because they see X blue eyed people while anyone with blue eyes sees X-1 blue eyed people?

The logic here is flawed. In a case where there are n people with blue eyes this does not work for n > 3. Because the chain of deduction breaks on day 2 since it is inpossible to gain any information about the number of people with blue eyes. If n=4 every person with blue eyes already knows the only possibilities are n=4 or n=3. Therefore there would be no reason to expect anybody to leave on day 2 because every person can see at least 3 blue eyed people therefore this not happening gives no new information. I guess what I'm saying here is that just because this describes a deciding algorithm that works if followed by all actors, does not mean that it is a correct chain of deductive logic.

5:40 what happens to the e^h - e^0 / h ???

4:20 And why no brown eyed people leave ?

Me on the island, not speaking a word: ☝️🙂‍↔️ 🫵🙂‍↕️

I think there's something lacking in the puzzle (please forgive me if I am wrong) It wasn't made clear if the people in the island know that there are 10 people with blue eyes. If that was the case a person with blue eyes would deduce that they have blue eyes when they only see 9. That way all 10 would leave on the first day. However if the case is (which I think this is what it is) is that there is an X amount of blue eyes in the population that of which no one knows the total. In other words no one knows that there are only 10 I think the puzzle would flow as explained? That and no one is allowed to talk to each other about eye colour (thus preventing the just ask someone what my eye colour is solution, logical too yes but not what I think this is going for.)

I’m so confused who gives a shit

But 0 is not an integer since definition of integer is X / X = 1, but you can't divide by zero thus it's not an integer

1:08 being at this point I have two things in mind First, the premise as initially presented would suggest that every islander would agree with the stranger's statement, if there is more than one person with blue eyes. Yet, the world builder in me wonders if there truly WOULD be multiple by this point. The question this really begs for me is: on what foundation is the agreement made that blue eyed islanders should leave on the ferry? Is it for a custom or belief that revolves around the particular nature of blue eyed people? Are they viewed as terrifying or wondrous? A citizen of the island would know which it is, so consequently wouldn't the most logical assumption rely on reading this expression in people's faces and thus assuming you're blue eyed? Which would mean that all blue eyed people, naturally illiciting this response, as well as some brown eyed people who misread the response would have already left the island. Which leaves the option that the stranger is lying or that some blue eyed people chose to ignore the signs. Which begs the question, what does it mean that they would leave of their own accord once they knew they had blue eyes? And why wouldn't people just tell eachother what their eye colours are? I mean if it's major enough to subject of a belief this defining, and unless it is shyed away from for being too sacred a thing, it would surely be part of every day conversation? So, the point we really end up at, to make away with the questions, is that if there are more than one blue eyed people remaining on the island, nobody would leave, if there's exactly one remaining, they alone would leave, and if there's none, everyone would leave or dedeuce that the stranger is lying.

cool puzzle. For some reason, the title made me think that the gist would be "adding information can cause more confusion". For example, if the stranger would have said nothing the solution would be optimized Does that logic ever make sense?

Oh, I thought the answer was they were going to shank the stranger for trying to disrupt the status quo. Woops

The video is a duplicate of a video of Ted Ed that was published years ago. No effort in the video has been made to give credit...

When i walk through it from the start it makes sense. But still, My brain cannot comprehend why the addition of a person adds a night .

This was kinda badly laid out. The way this video was structured suggested that the fact there are 10 blue eyes people is within the common knowledge, thus the day thar every person realizes their own blue eyes would never change, it would always be day 2.

“At least one of you has green eyes” ahh puzzle

If you know there are only 10 blue eyed people and you count only 9 then you must have a blue eye

Level 3...x=6/0...how you derive to second equation x x 0=6. Implying 0/0 =1

“You have blue eyes”

if there are 10 blue eye people and i see only 9 that means i'm the 10th one. Day 1 all leaves problem solved. why so much chaos in the solution ?

The beauty lies in the fact that as soon as all of the blue eyed people have left the island, all brown eyed people would know their own eye color.

A group of perfect logicians would ask of what importance a person's eye color has, and anyone enforcing the segregation of eye colors would do as mandate, and not by self-regulation, I would say.

Great puzzle! Its tough to say what’s the most interesting thing about it; that they somehow can’t speak about eye colour, or that they’re literally enabling a genocide of blue eyed people 😂

You said they were perfect logicians, Never that they were also perfect statisticians. 🙃

If they knew they were forbidden to talk about eye color, wouldnt they just kill off the stranger?

the only one blue eyes not a logician: Oh, I never thought there are blue eyes on this island. That's fresh. day 2: Wait... where's everybody gone?

This is so much more wholesome than the version my set theory professor taught us, we had a travesty of 400 ducks committing ritual suicide after a visitor arrived and said “ah, so good to see another duck with blue eyes”.