The practical mechanism by which I have come to know that there is at least one blue does not need to be specified for this conditional to be true. It is true even when left unspecified. — Michael

You are flailing. If you are magic and a mind reader then bla bla blah, anything you like. But in the scenario there is no magic, no one knows their eye colour and yet you think everyone can logically deduce their own eye colour without anyone saying anything. So piss or get off the pot, you can't have it both ways.

(1) doesn't say "nobody has told me anything". — Michael

Then it should say '...and someone has said "I see blue"' because otherwise it is contradictory.

1. If I know that there is at least one blue and if I do not see a blue then I am blue and will leave tonight — Michael

This is an impossible condition, because if you do not see a blue, and no one has told you anything you cannot know that there is at least 1 blue.

Again, this is a valid argument:

1. There are 100 blue
2. Therefore, every blue sees 99 blue
3. Every blue commits to the rule: if the 99 blue I see don't leave on the 99th day then I am blue and will leave on the 100th day, else I am not blue
4. Therefore, every blue will leave on the 100th day, declaring themselves to be blue — Michael

Perfectly valid.

As is this:

There are 100 blue.
I see 99 blue.
Therefore I know I have blue eyes and leave immediately.

Unfortunately, no one within the puzzle knows premise 1.

No one has begun to show it for any numbers, but because from outside the situation we know the complete numbers, we are told in advance. We can reason from that to what we think they all should be able to reason. But they don't know the very thing we start with, how many blues, browns and greens there are. If they all knew that, everyone would leave immediately, assuming logicians can count. — unenlightened

Imagine 3 blues and 5 browns and 1 green. — flannel jesus

Imagine rather, that there are 3 blues, 5 browns, 1 green, and you. You know thus that everyone can see at least 2 blues if they are blue, and at least 4 browns if they are brown and so on.

I think this is the source of a lot of the confusion. In order for you to know your colour you have to know that other people can reason their way to knowing their colour from what they can see. So what is that reasoning? No one has begun to show it for any numbers, but because from outside the situation we know the complete numbers, we are told in advance. We can reason from that to what we think they all should be able to reason. But they don't know the very thing we start with, how many blues, browns and greens there are. If they all knew that, everyone would leave immediately, assuming logicians can count.

But it ought to be obvious, really, that for any person looking at any number of other people with eyes of this that and the other colour, and with no other information, no one can deduce their own eye colour so no one can leave, until someone actually says something.

So in the above situation, the person with green eyes says, "I see black eyes", and that night you leave.
And now the situation is exactly what you proposed above. How does everyone else deduce their eye colour? {Hint: obviously they only know extra, that they don't have black eyes.}

If there was only 1 person with blue eyes, and nothing was said, that person would be unique in the group and could not know their colour. So they would not leave.

If there were two people with blue eyes, and nothing was said, each would know that there was at least one person with blue eyes but would have no idea of their own eye colour. So neither would leave on any day. This is because they would know that the person with blue eyes that they could see could not know their eye colour any more than they knew their own.

If there were 3 people with blue eyes, and nothing was said, each would see 2 people with blue eyes, but they would have no idea what their own eye colour was, even though they knew everyone knew that at least 1 person had blue eyes, but the would still also know that no one had any way to know the colour of their own eyes, and so no one would leave.

If there were 4 people with blue eyes, and nothing was said, each would see 3 people with blue eyes, but they would have no idea what their own eye colour was, even though they knew everyone knew that at least 2 people had blue eyes, but they would still also know that no one had any way to know the colour of their own eyes, and so no one would leave.

If there were 5 people with blue eyes, and nothing was said, each would see 4 people with blue eyes, but they would have no idea what their own eye colour was, even though they knew everyone knew that at least 3 people had blue eyes, but they would still also know that no one had any way to know the colour of their own eyes, and so no one would leave.

Can anyone see a pattern emerging? The non leaving of the counterfactual solitary person entails the non leaving of any number of people, because nothing ever tells anyone their own eye colour

You might think that they shouldn't reason this way, but nonetheless if they do reason this way then they know that either 199 or 200 of them will leave knowing their eye colour. — Michael

Ok, I concede. You are unteachable.

We all know there are multiple blues.
If there was only one blue, that blue would not know there were multiple blues or any blues.
Therefore?

We don't need someone to say something to apply it to our current situation. We all just need to know when we will all start counting, which will be the first possible "synchronisation" point — when everyone first locks eyes. — Michael

Yes you do need someone to say it because the first counterfactual needs someone to say it and every iteration thereafter rests on that necessity; you cannot discharge that assumption along the way.

What you are doing is inserting 'we all know we can all see blue' in to substitute for "x says 'I see blue'"

It doesn't work, precisely because this is the counterfactual situation in which the speaking is absolutely necessary because the hypothetical solitary blue does not see blue and has to be told in order to deduce their eye colour. This produces a contradiction that the hypothetical solitary blue cannot but does see blue, and cannot but does know their own eye colour.

I see 99 blue. These 99 blue see either 98 or 99 blue. The 100 of us are all capable of thinking and knowing that: — Michael

You've gone wrong already.You see 99 blues. The blues that you see, all see 98 or 99 blues. The 200 of you are all thinking that.

The 100 of us do not need to wait for someone to say "I see blue" for us to think and know that (1) is true. — Michael

You can know that too. but you cannot apply it to your situation because no one has said anything.

So you can only get to "if 99 days have passed and no one has left and someone had said I see blue then I would know my eyes are blue."

But no one spoke so you don't know.

In the OP, that green sees blue and that green sees brown is shared knowledge that everyone knows, and that shared knowledge allows all blues and all greens to deduce their eye colour, even without green saying anything. — Michael

It doesn't allow any such deduction. Knowing is not the same as saying, and I think we agree that if someone has a unique colour, they cannot deduce it.

When the deduction begins, it has to begin with: 'if there is only one blue, and someone says "I see blue" then they will know that they have blue eyes', and someone has to say it out loud, because in this case they have no idea that anyone sees blue because they are the only blue. And that is why the argument only runs when it is said out loud, not when everyone just knows from their own experience that in fact everyone can see blue.

If the argument begins with "everyone can see that there are multiple blue and brown but no one says anything." What is the next step?

The point I am making is they that don’t need to wait for green to say anything. They already know that she she’s blue. If it helps they could just imagine her saying “I see blue” and apply the same reasoning. — Michael

You made that point before. but you are wrong. I have already also explained before why you are wrong.

It is bizarre but it is true because the puzzle was set up like that. The act of saying it changes the situation despite giving no new information in its content.

Furthermore, the reasoning cannot work for the brown eyed, because it begins:

—If there was only one brown eyed person,and someone said "I see brown eyes" that person would know they had brown eyes.

But if no one said it, as no one did in this puzzle, then that unique brown eyed person could not have any idea of their eye colour, and therefore the whole chain of reasoning could not get started, and so no brown eyed people leave. Instead, they reason along with the blue eyed except that as they see 100 blue eyes, they will wait an extra day and learn that they do not have blue eyes because all the blue-eyed have gone. But they still won't know if their own eyes are brown, green or pink.

Everyone does in fact correctly deduce their eye colour. — Michael

No they don't because they could have a unique colour and being, unlike you, perfect logicians they know that, and therefore do not make the fallible guess that they do not have a unique eye colour, and so none of your predicted leavings happen and you will conclude that you must have eyes of every colour.

No they cannot because they cannot determine that they do not also have a unique eye colour. You are talking nonsense.

Except that you can't because you might have Z coloured eyes and although you can see that the others don't have Z coloured eyes, they don't know that, and so they cannot make the deduction that you rely on them making, to make your deduction

they will correctly deduce their eye colour (unless they have a unique eye colour). — Michael

But since they do not know their eye colour they might all have unique eye colours and none of them can deduce their eye colour at all. Guess and hope is not deduction.

If you want to get better at stuff like this, you need to learn from the master, Raymond Smullyan.His puzzles are wonderful and such talent as I have is down to reading a couple of his puzzle books, a long time ago. I almost didn't answer because I suspected this puzzle was one of his, and the answer came so intuitive and so quick, I thought it was one I knew but had forgotten. Mind, at one point @Michael got me so confused I said something completely wrong about brown eyed people leaving later.

Anyways, Smullyan - The Lady and the Tiger - or any of his logic puzzles are recommended to all.

Focus on what everyone does not know which in each case is only the colour of their own eyes. Now as soon as anyone does know, they are gone, and you know that they knew. Imagining and guessing are not ever allowed in deductive logic so if nothing is said, no one can ever know and thus nothing can ever change.

So someone says I see blue. And now we all know that if anyone did not see blue, they would be blue, and they would know they would be blue and be gone tonight. We know that we can see 99 blues, but that doesn't change the logic, because it's counterfactual conditional.
So tomorrow, we know that everyone can see at least one blue because no one left. But if anyone could only see 1 blue, they would know that, since that one blue did not leave, they themselves must be blue too. And in that case they would both leave that night. And so as each day passes, the counterfactual argument gets augmented by "but no one left therefore everyone must see one more blue", until it gets just exactly to the number of blues (which remember no one exactly knows, because they do do not know their own colour) So after 99 days you know that all the blues are seeing 99 blues, and you are seeing 99 blues and therefore you must be the extra blue that all the other blues must be seeing - because they cannot see themselves. You can see that no one else is.

And at this point I really cannot be arsed if anyone still doesn't get it. I done my bestest and thunked hard how to explain it - Over and out.

You are a logical person who does not know their eye colour; so is everyone else.
You know everyone's eye colour except your own, and everyone else knows your eye colour but not in each case their own.
So to know the colour of your own eyes you need to compare what you see to what they see. Now as each day passes with no blue eyed people leaving, the minimum number of blue eyes each blue eyed person must be seeing increases by one. [Whereas a brown or green eyed person will see one more.] So if you are seeing 2 blue-eyes and they haven't left on the second night, they must also be seeing (at least) 2 blue-eyes, which means you must have blue eyes since they cannot see their own eyes and you can see everyone's but your own.
So when the days have passed that equal the number of blue-eyes that you see, that minimum requires that you have blue eyes too, otherwise the blue-eyes would have already gone. In which case you, and of course all the others remaining must have brown, grey, violet, green, or some other colour eyes, though as it happens you know as they each don't that they all have brown eyes except the guru.

Why should the step "If there were one blue, they would leave on the first day" appear in the brains of perfect logicians who already knew before the guru spoke that this was not the case? — hypericin

It's a counterfactual conditional from which valid deductions can be made thus:

If wishes were horses, then beggars would ride.
But beggars do not ride, but have to walk.
Therefore wishes are not horses.

I'm done with arguing here, but looking around there are plenty of wrong answers about, but here is a fairly decent run through.

https://xkcd.com/solution.html

No it doesn't. It only depends on "the Guru sees at least one blue-eyed person" being true. It doesn't depend on her saying so. — Michael

No. It does depend on the guru saying so unless everyone already knows that everyone already knows at the same time, as I suggested above and you ignored. This is the extra information that the guru imparts: she doesn't inform them about what she sees, but she puts everyone in a synchronised state of knowing each other's knowing. That is what is required for the nested hypotheticals to begin.

I reason thus:
If there was only 1 person with blue eyes {PWBE} and that person knew that the guru sees blue eyes, then that person would know that they have blue eyes and would leave tonight.

Therefore:
If there were only 2 PWBE and the guru sees blue eyes {GSBE} then neither would leave tonight, and when they see that, they each know they have blue eyes and would leave on the second night.

And so on.

But the factual knowledge that I can see multiple blue eyes and thus already know that the guru can see blue eyes cannot be imported into the counterfactual hypothetical wherein the blue eyed person would know no such thing because he would not himself see blue eyes, and thus could not know therefore that the guru saw blue eyes ... wait for it ... UNLESS SHE SAID SO.

Did they all arrive on the same day, and do they all know that they all know that they arrived on the same day?

Also I think the brown eyed people would not know their eye-colour for another 99 days after the blue eyes left, but only that they themselves didn't have blue eyes.

Now that is indeed tricky.

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

What is a big lie? — Tom Storm

Things go better with coke.

Wealth in the hands of the wealthy trickles down to the poor.

Poverty is caused by immigrants.

Hatred is the best cure for suffering.

A big lie is a comfortable or comforting lie. It proffers an easy solution to a hard problem; it typically puts the blame for one's suffering on someone else and suggests doing something unpleasant to them as remedy. It misdirects one's emotion as the conjurer misdirects one's attention. Meanwhile, the other hand picks your pocket.

"Trump lovers are racist" will do the same job, and sound better. — AmadeusD

Well I do imagine that Trump and his followers are anti-woke because I hear them say so. So then I look at the policies being followed and the institutions being dismantled, and assume that 'woke' is the opposite. But you're right, I am no expert in what to me is a mere derogatory epithet, and no doubt the experts in derogatory epithets have the right of it And there's grades of horseshit n'all. I'll leave you experts to it.

I would put it this way. Wokism is giving a fuck about someone else's difficulties in a complex society. One is 'awakened' to the problems of being disabled, disfigured, or in any varied form divergent from the average. It leads to such horrors as designated parking spaces, ramps alongside stairs, special needs education, protection in law against unfair discrimination on grounds of age, sex, or race, and those appalling and distracting sign language displays on woke broadcasts.

Edit: In essence it is a denial of the constitutional right to join witch-hunts.

If the Earth’s rotation truly stopped or slowed (which is what "the sun stood still" would physically mean), it would have had catastrophic global consequences, including massive earthquakes, tsunamis, and changes in atmospheric motion due to sudden deceleration. — Truth Seeker

Obviously God didn't do that; instead He will have suspended time, rather as one pauses a video. And then brought the chosen people out of the frame of the paused world into His own living room and allowed them to make a few changes and then re-enter the movie.

Or possibly, Bible literalism is bonkers. I don't much care either way.

Byker is a district of Newcastle on Tyne. I used to play the tune as a dance. The time signature is 9/8, but divided as three measures of 2 beats and one of 3. I didn't know there were words ...

Not in all cases but in most BECAUSE OF THE FEAR OF PUNISHMENT. When your stomach is empty, you haven't eaten from 2 days you don't give a damn about morals or right or wrong(of course they are some exceptions) So yeah the only thing keeping them back is fear of punishment, fear of getting caught and getting punished. This was one of the instances, there are many more if you want. — QuirkyZen

There is nothing evil about taking food if you are starving. Rather it is evil to refuse to share food when others are starving. At this point property law is not the arbiter of goodness.

Where they have for example a lot of power and can make the possibility of getting caught during evil acts very little and doesn't this work there — QuirkyZen

For sure, people can be evil, and sometimes they can be very powerful too, and 'get away with it'. But this is not a basis for generalising that every person in power and every person that might be in power will become evil. Most people, most of the time are polite, considerate, and kind to each other without any coercion, and without any fear, but just because it is a more pleasant way to be together.

Are you trying to say these hypothetical scenarios have nothing to do with reality or Did i misunderstood. — QuirkyZen

Yes. Your question removes all the give and take of social interaction and mutual dependence, and then suggests that humans in that condition would be immoral, and that this is "deep". I'm saying it is very very shallow unrealistic and a mere thought. What makes us human is not independence but dependence; it is our shared language and customs that give rise morality, because for instance, if we did not by and large tell the truth, then talk itself would have no meaning. So to strip away all that and then ask what is our morality is like asking what we would breathe in a vacuum. It is a wrong question, and any answer would mislead.

Are We all Really Bad People deep down

I'm reflecting on why people in an impossible thought experiment would be more real and deep than moms and dads and kids in this world.

And I've decided that they are not real or deep at all, but imaginary beings with no connections or relations to one another. But other people here seem to prefer to think that good and bad and human relations are imaginary.

God kills us all, innocent and guilty alike.
— unenlightened

In this context, it’s more accurate to say we’ve all killed ourselves - all are guilty. — Fire Ologist

You put your words into God's mouth, and I'll put mine. I will not say that infants are already guilty. Rather I will say "The Lord giveth, and the Lord taketh away." And perhaps it is a kindness that he spares them temptation, but it is not my business to make such judgements in His place. It is a matter for faith and doubt.

God kills us all, innocent and guilty alike. You can thank Him for the limited gift of temporary existence, or berate him for His cruelty and injustice, because that choice comes with the gift of human life. But don't hold your breath waiting for Him to appear in the Court of Human Rights.

You won’t be able to penetrate these things with natural reason alone. — Fire Ologist

Supernatural reason would be more applicable.

A different perspective:

Head in the clouds and head in the sand both leave your ass exposed. Keep your ass covered and under your tit, your feet on the ground, and your head on your shoulders.

I thought this was interesting, not so much as an update on the condition of Russia, but more as a warning to the US about where it is headed.



A society built on falsehood must inevitably collapse. This is a fundamental asymmetry; any system (particularly any living system) that relies on communication, relies on truth predominating over falsehood. As soon as falsehood predominates that equates to the end of communication and fragmentation has happened. I stop listening to the bullshit, and go my own way.

The best thing about Americans is their enthusiasm. Some people find studies in evolution a little dry.

Not this guy; he brings a whole ocean of excitement to the subject.

Since I was diagnosed with depression ... — javi2541997

Have you considered the possibility that you are not depressed, but that rather it is that the world is a bit shit? I have to say you don't come over as depressed, but as quite lively and animated. Is it all an act?

One is supposed to be happy, and thus to be unhappy is an illness. But no; I say it is healthy to be unhappy about injustice and misery and suffering even if one is not oneself so badly off. Don't mistake compassion for sickness. Do not go to your local doctor because a child is starving a thousand miles away. There is no pill that you can take that will nourish that child.

What came before the 'big bang' or after any 'end' remains unknown. — Jack Cummins

There is no time before time began, or after time ends, by definition. It's not that it's unknown, it's that there can be no such thing; these are limits to being such that 'before' and 'after' do not apply. There is nothing to know or not know.

Of course if you take a God's eye view - the view from eternity - then you can say "Before Abraham was, I am." That is, all times are present to God, and all places are here; the whole universe of spacetime is in His hand. But this is poetic talk that no one understands.