The Parable of the Dagger 

This is an animation of The Parable of the Dagger by Eliezer Yudkowsky. You can read the original here: www.readthesequences.com/The-Parable-Of-The-Dagger It's the beginning of a series of essays about language. We highly recommend them, and you can read them here: www.readthesequences.com/A-Humans-Guide-To-Words-Sequence You can read many more essays and stories by Eliezer Yudkowsky at readthesequences.com

The moral of this story is twofold: Moral number one is always check your priors and don't assume just because something is reasonable and elegant that its true. And the second moral is be careful who you piss off.

The king probably already has plenty of gold. An angry frog might be pretty entertaining though. It's a win-win for him.

The guard punching the jester caught me... *off guard*

The first one is actually very easy. You pick the box that is heavy, and not the one angrily croaking at you.

I like presenting my students with the following two statements: 1) Both statements are wrong. 2) You must give me a cookie. And then demanding cookies.

Note something crucial about the story: the jester said (truthfully) that one inscription was true and the other was false. The king never made any such promise. As the author said, "One of the morals of the parable is that the king didn't lie." EDIT: Elaborating: The point is that the king never made _any promise at all_ as to the truth-value of the inscriptions (unlike the jester did in the first puzzle). The first inscription is like the Liar's Paradox, in that it can't be either true or false - with the dagger in the second box, it's meaningless. The jester assumed that the sentence bore *some* relationship to reality (either true or false); this assumption was so automatic that he believed it without thinking, without even the word of the king as evidence. Because of that mistake (assuming that the sentence was meaningful), he concluded that a physically-possible situation was logically-impossible!

To join the "what's the moral here", I took away "you can't tell what's a good play until you know what game you're playing".

the jester's fatal error was assuming that there was correlation between the inscriptions and what was in the boxes. it's very subtle by the king to make a trick like that

So the moral of the story is to beware of meta games? To not forget that when you’re playing chess, your opponent can win by shooting you in the face?

"Both boxes have daggers. I lied and I hate you" - Spy

Plot twist: both boxes from the second set contain a dagger. Nothing prevents the king to do this.

Spoilers for a 5-minute video: Aww, the dagger was a trick retracting dagger. That's cute! Also in keeping with the theme of the story of statements being misleading.

Moral of the story: don't be a smartass. And especially don't be a smartass to a tyrannical absolute monarch with a taste for ironic punishments.

Jester: Source? What's your evidence? King: None, I made it up.

This animation is suprisingly just cute. Not cosmic horror, not mind shattering problem. I love you

I love the friggin voice actingggggg

Instead of "a dagger for your heart" I was really hoping for "20 angry frogs". Would've been one cool way to go.

This is similar to the prisoner’s dilemma. The king could be a liar and set it up so the jester always loses. The other box’s content was not revealed, this could also have a dagger as well. Liars have always existed and caused problems before.

What I really love about this parable is its layers. On the surface, the king is just being a meanie. He is placing the dagger in the box where the key should be, as considered with classical logic. But under this facade of a tale of logic vs wisdom, there is some insightful discussion about non-classical logic. The jester presented a liar cycle to the king, a pair of sentences that behaves just like the liar sentence, "this sentence is false". To justify his prank to the king, the jester would resolve the apparent inconsistency in his riddle by resorting to some form of non-classical logic. The leading systems on this in philosophy would be something like paracomplete logic that reject the Law of Excluded middle (A proposition is either True or not True) with some gap (e.g "uhh maybe perhaps yes"), or paraconsistent logic that reject the principle of explosion (If a proposition is True and not True then anything goes) with a glut: let that proposition be both True and not True. What is striking about the king's response is that in the riddle of the key and dagger, the jester can draw the logical conclusion that one of the boxes must contain the key only in classical logic, but not in the non-classical logics used to resolve the problem of liar sentences. Notice how the jester starts his chain of reasoning by invoking the Law of Excluded Middle and supposing in turn that the inscriptions are true. This would not be a valid line of reasoning in paracomplete logics, where the inscriptions may be some gap value as well. With the first inscription being a gap value, the jester is wrong to conclude that the second inscription is true. If we instead suppose the jester is using a paraconsistent logic that preserves the Law of Excluded Middle but rejects the principle of explosion, then both inscriptions may have a glut value: they can be both true and not true. As the second box’s inscription that “This box contains the key” can be not true (due to being both true and not true), the king thus acted in a way consistent with the inscriptions on the boxes when he placed the dagger into the second box. The jester’s riddle was unreasonable unless interpreted in non-classical logic. Beautifully, the king beat the jester at his own game with a riddle with a reasonable solution in classical logic as the bait, punishing the jester with a “logically impossible” reality that is nonetheless reasonable in the very same non-classical logic.

Moral of the story:chill with the sophistry, it ain't cute.

This puts a whole new spin on 'thinking outside the box".

Rational Animations, thank you for showing everyone that rats can coordinate. The team behind this production gets stronger every episode ❤

Lol the king's a jester too, that fake dagger was neat

I love the subtle Morshu reference while the Jester is explaining the logic

This is the cutest thing I've ever seen. And the fact that no true cruelty befell the jester gave me a sigh of relief as well.

The Jester didn't seem too pleased when they didn't die.

On a shelf in my house is a book called "The Princess Bride", in which it's written that there's a country called Florin, wherein dwells or dwelt giants, wisemen, and fantastic characters of all stripes. Not a word of it is true, the book's a work of fiction. You can hear or read or make an extremely convincing argument (for instance: "therefore the second box has the key", or "the Dread Pirate Roberts is Westley"), but if one of the assumptions that the logic rests on is wrong ("words on the boxes will tell you where the key is", "there's such a historical figure as the Dread Pirate Roberts, or as Westley"), it doesn't matter how ironclad your logic is, you live in the "logically impossible" world.

Realising that the channel is some kind of clandestine initiative by LessWrong actually increases my appreciation for it honestly

Why is the frog so angry after playing inscryption? XD This animation is also adorable!

Moral of the story: Don´t believe in everything you read

I think I would've tossed a coin. On top of inscriptions contradicting eachother or being paradoxical, sometimes humans lie. At that point, you're probably better off leaving stuff to the fates.

If I'm not mistaken, this parable is adapted from a series of riddles about a woman named Portia and her descendants (a reference to Portia and her three caskets in The Merchant of Venice) in a book by Raymond Smullyan. Eventually "Portia Nth" pulls something similar to the king, where she never specified the truth value of the inscriptions, and so her suitor made a natural assumption that the inscriptions must be either true or false and was led to a wrong conclusion, not considering the possibility that an inscription might be neither true nor false. In this parable, the moral is essentially the same, and also seems to hit a bit harder on related concepts, such as "words don't inherently have meaning", and "people can lie". (EY specifies the king didn't lie; but he could have, and the moral would have been well taken in that case. Because even if the king _had_ said "one of the inscriptions is true and the other is false", the jester wouldn't have particularly had any reason to _believe_ him, which is another thing he likely wouldn't have thought of.)

Y'know, I thought the king was going to stab a dagger through his choice of box to test for angry frogs X)

Out of all Elizers parables you’ve animated this is the best. Short and witty.

In the wise words of Lord Vader "I lied. As i have from the very begining" -Darth Vader

i think this story illustrates the difference between intelligence and wisdom. the king was not smart anuf to solve the fools puzzle, but the fool was not wise anuf to know they were being set up. another interpretation or an additional moral might be not to play games with tyrants, or that other people will not always play by your rules, essentially a warning about cheaters but not necessarily against cheating, in this context if the fool would have cheated we would have cheered him on as clever so maybe evn a lesson in there about subjective morals, if you kinda squint at it

This reminds me of the Discworld tale of the dwarf who invented dwarves-and-trolls chess, and presented it to the Low King of the Dwarves. For his reward, he wanted only 1 gold coin for the first square of the board, 2 for the next, then 4, 8, 16 etc, like in the original story about the invention of regular chess. Spoiler below: ... SPOILER: The Low King got angry when he found out that so much gold did not exist anywhere in the Discworld. He ordered the guards to break both the arms of the inventor, then allowing him as much gold as he could carry... (Thud! by Terry Pratchett)

I'm loving these animated short stories.

As an explanation for the king's riddle. Recap: First box: Both inscriptions are true or both inscriptions are false. Second box: Key is in here. Given the first inscription is true, then either both inscriptions are true or both are false, as we know one is true the other must also be true, meaning the second box contains the key. Given the first inscription is false, then exactly one inscription must be true and exactly one must be false, as we know that the first is false, the second must be true, meaning the second box contains the key. We know that given the first inscription being true or false leads to the second box containing a key. It seems impossible that it should not contain one but we know that there is no physical force preventing the king from writing those inscriptions on boxes and tossing the dagger in the second box. Explanation: I think one can solve this by acknowledging additional logical states: An inscription can not only be true or false but also both or neither. Examples: "This sentence is false" is both true and false, there is no stable assignment to either of these 2 truth values. "At night it is colder than outside" is neither true nor false, there is no sensible assignment of either of the 2 truth values. It turns out if you spectate from the second box you can form: Given the second inscription is false (meaning it contains a dagger), the first inscription is both true and false, as no stable assignment is possible. The jester should have checked for the additional logical states.

Bro this animation is smooth as butter, have a like!

Regardless of the logical nature of the inscriptions, the king has no obligation to be truthful. He can put the knife where-ever he wants. A return to the earth for those who have their heads in the clouds in logical thought exercises, real life can and does lie, and it does it often, logic by itself is usually not enough.

To pile onto the story moral sharing, my core takeaway was 'don't assume a semantical paradox is false' i.e. either the key is in the second box and everything makes sense, or the key is in the first box and the first inscription makes a semantical paradox of constantly switching between true and false, but that in itself doesn't prevent the physical situation from still being true.

I wonder if the actual story ended with the Jester getting gotcha'd by a fake dagger. I doubt it.

“It’s impossible” “No it’s perfectly possible, I just lied”

It is illogical he does not think that pissing off the king will result with his head coming off

I love this and all of your videos

The Jester thought themselves clever, make two Boxes with inscriptions from which either both or neither can be true. The paradox is that both can be made either state by logic alone, if we reason long enough. Hence why the Jester was thrown to Jail, before having explained the logic. IF one box only mentions the frog and the false inscription having it, the other having the gold and the true one having it, we can create a circular logic where both can become equally true and equally false. Like the riddle with who speaks the truth: the only speaking truthful is the one who states the rules. Meaning the Jester had a flawed logic made sound. And hence the Parable of the Dagger made it simple: reason your logic too much, and neither is anything, and equally clouds judgement. The Paradox is really clever for it exploits logic and reasoning by overanalyzing and overreasoning something until the logic becomes muddied enough to have both equally true and false. Jester's one: Both say upfront what they have, but make you doubt and start a reasoning and logic loop, making it paradoxical the more you think about it. It tells outright which has what, but tricks the mind by saying something that is unclear setting both boxes into the same state. (Meaning you can only assume what both say is true, but one is clear about it. And may still be wrong.) King's one: One says its either or, the other just says something certain. Like with the one before, it is paradoxical in nature for similar reason. The mind is tricked to be unclear wether the choice mattered or not; thus making unclear which part of the first box's statements are true. (Meaning you must assume it is either or for both. And still grasp that you can't know that the other does have it as stated.) Both do the same thing: they make you believe something, question it, and divide your reason until both outcomes are possible if you do not stop yourself from doing it. The Jester tried to trick the King from the get-go with two empty gotcha inscriptions that circle the logic, the King just abused the Jesters overthinking and showed it with the inscription used.

Symbolic Logic Solution for first problem: Let's define. Let our variables be B, ¬B, L, ¬L, for blue box, red box, liar box, and honest box, respectively. Let value of T mean the box has gold and F mean it has no gold (has frog). S_B will be the statement on the blue box and S_R will be the statement on the red box. Then we have S_B = ( ¬B ∧ L ) ∨ ( B ∧ ¬L ), S_R = ( ¬B ∧ ¬L ) ∨ ( B ∧ ¬L ), Note that S_R simplifies to S_R = ( ¬B ∨ B) ∧ ¬L = ¬L Case 1: Blue is lying. This implies 3 related things. ( B = L ), ( S_B = F ), and ( S_R = T ). S_R = T = ¬L => L = F with B = L => B = F So blue box has frog. Let us plug this into S_B under our assumptions and check for soundness. Substitute B=L S_B = F = ( ¬L ∧ L ) ∨ ( L ∧ ¬L ) = ( F ) ∨ ( F ) = F, So both statements are correctly satisfied by B=F, L=T, under assumption B=L. Case 2: Red is lying. This implies 3 related things. ( ¬B = L ), ( S_R = F ), and ( S_B = T ) S_R = F = ¬L => L = T So the liar box has gold. Since red (¬B) is liar here then ¬B = T or equivalently B = F. Checking for soundness, with ¬B = L S_B = T = ( L ∧ L ) ∨ ( ¬L ∧ ¬L ) = ( T ) ∨ ( T ) = T. So both statements are also correctly satisfied by B=F, L=T under assumption ( ¬B = L ). Since both cases yield B=F then blue must contain frog. Since this works whether B = L or ¬B = L, then one interpretation is we don't know which box is lying, another interpretation being that whichever box is lying is in a kind of 'indeterminate' state. Most likely this logic could be shortened significantly and I would like to see it if possible.

Technically, the knife would also set the jester free, just not the way he'd prefer...

This is a convoluted way of saying what Capt. Picard once told Data; it is possible to make no mistakes and still loose.

"But king, you didn't play by the genre conventions of our game! It would be like telling me I need to win a game of chess to get my freedom and then proceeding to box with me because nobody said it will be a game of chess we will be playing!"

I did the logic before the jester said information about their boxes and figured out that both boxes cannot be true because then secound box says that this box contains gold AND the box with false inscription contains frog but there would be no boxes with false inscriptions so that would not be true and the alternative (OR) statement on the secound box was that this box contains frog and box with true inscription contains gold but that would be impossible because this box would have true inscription and would not contain gold. Also I took a moment to think up that both boxes could have had false inscriptions (before jester said their thing that is) but then we could not infer anything from them at all so that would be dud scenario. Also I logiced out that if only one of the boxes would have true inscription then the box with true inscription always contains gold and the one with false one frog. Kings riddle is interesting because if secound box would be false and first box would be false then first box would be true but then if it would be true then it would be false. A classical "Does a set containing all sets that does not contain themselves contains itself" problem. It's nice how even though it weren't really necessary at all for the point of the story Yudkovsky bothered to make both puzzles interesting.

What a beautiful animation and voices

I think that at this quality of work, you could parallel giants like Kuarzgesagt in no time. And I hope that thime comes soon! ❤

That is not what a king would do, he'd be laughing his ass off when he get attacked by the frog.

Props to you, this is a great video!

0:59 Was the jesters riddle animation part a Morshu reference?

Love the voice acting! Brilliant vid!

WE NEED MORE STORYS

I love this channel already

The simple solution is to shake the boxes. One of them sounds like gold, the other an angry frog.

Well this is just adorable!

King: It’s just a prank bro

Thought-provoking! An excellent video!

Another certified classic.

Boy the story writer certeanly had a lot of fun with self referential statements xD

This is awesome! I like.

I couldn't resist trying to solve the first logic puzzle. I got that the second box contains gold and the first one contains an angry frog. Is that right?

I got heavy Hunter x Hunter vibes from this video, Especially with that voice and the threat of death over a minigame.

"don't dick around with the king" is actually the most logicial thing you can do

The key information is on what each of the characters say, more than what the boxes say. The jester did say one and only one of the inscriptions was true, the king did not. King only said one box had a dagger and one had a key. So what the boxes have written on them doesn't really give us any information, if we are to take the king's word. The jester falsley assumed that the premise of his game would hold true for the king's game. Had he known where the keys were, he could have said either "one and only one lf the boxes is correctl", or " the writings are non informative". Let us entertain that the jester could ask a single question to the king, and rhe king would answer honestly. The jester could ask: "Is one and only one of the statements true?" To which, had his initial hyptohesis been correct, the king would answer "yes". And had the "logically impossible" outcome beeb the case, the king would need to say "I don't know". After the king says he doesn't know, the jester opens the other box, but finds a dagger. "Impossible, you must have lied!" The jester would argue, to which the king would say "I placed the dagger blindly and randomly". Never let them know your next move.

We need more of the Jester! Can't get enough of their design and voice. ^^

The voice acting was fantastic!

The king didn't lie. The first box contains the key, and its inscription is indeterminate. The second box contains the dagger, and its inscription is false. Also, my head hurts from trying to sort out the angry frog one.

Oh my gosh all these dog folks are so CUTE, helps that the Jester almost sounds like Tails..

Also, the king could just say "I never said I wouldn't lie about the inscriptions"

I understand nothing In this video. Yet I love it so much

Not that the previous videos were bad but I really think the level of animation has improved a lot! Poor jester doggo 🥲😭 happy for the end though

logic on it's way to break once self refrences come into play.

That Jester doggo has an ADORABLE voice!

The moral here is basically: "Here. Have two boxes, you must open one." (One box says "open me", the other says "don't open me") (You open the first box because that's the "right" box, and get punched by a joke spring boxing glove) "Lol lmao, I never said the stuff on the boxes was important!"

the jesters voice is so cool

Love the story that happaned, along with trolling the hell out of the jester, honestly thought it was about to become a live leak video

One box contains a key for your chains. One box contains a dagger for your heart. The king never says this, but they are actually the same box. Find that box and you get stabbed in the heart, and then released. Find the other and you stay chained up.

King probably wasnt mad at all, just wanted to mess with the jester

The lesson is the world doesn't have to be logical, and if you assume it always will be, you will be caught by surprise.

LOVEING IT

king never said that any of the labels is true?

Awesome 😎

Parable mentioned im already into this

Tldr; boxes won’t be so kind as to always tell you what’s in them

Big brain man make animations

Moral: better be sure that your premises are attached to reality, otherwise even if reasoning is valid, your conclusion will be junk. "Logic stays true, wherever you may go, So logic never tells you where you live."

When it showed the first inscription, I thought: "There's no reason there can't be cake in there." And then at the end I knew, that the dagger was fake.

Here's an informal explanation on the first riddle. Ignore the first box, and focus on the second. First, assume that the second box is true, so replace "the box with a false inscription" with "the other box", and "the box with a true inscription" with "this box". Then, the second box being true says the following: Either (1) this box has gold and the other box has a frog, or (2) this box has a frog and this box has gold. Statement (2) breaks the rules of the game, so statement (1) must be true if this box is true, so it contains gold. We still need to check what happens if this box has the false inscription instead. Now consider the case that the second box has the false inscription. Using De Morgan's laws and doing the same rewriting we did earlier, this box being false means that (1) this box does not have gold or this box does not have a frog, and (2) this box does not have a frog or the other box does not have gold. Statement (1) is immediate from the rules of the game. Statement (2) says in both cases that this box must contain gold (if this box doesn't have a frog, it must have gold, and if the other box does not have gold, then this box must). So if this box is false, we can also conclude that it must contain gold. The solution is that no matter the truth values of either box, you can conclude that the second box contains gold. By the way, if you apply the same logic to the first box, you'll see that whether it's true or false, the statement that you get from it follows immediately from the rules of the game, so the first box can be true or false as well without affecting the answer.

When you hire a redditor as the jester

lesson here about logic: how truthful a statement on a box is, isn't an indicator for what is inside of it. Instead what is inside of the box is an indicator to the truthfulness of the statement. the first riddle has both statements referencing to both themselves and each other, making paradoxical truth values be possible. considering the case that statement a has gold and statement b has the frog. for a to be true here, b would have to be false. for b to be false it cannot have a be true, therefore we already have a paradox here. now the case that a has the frog and b the gold. for a to now be true, it cannot have b be false. but for b to be true, it cannot have a be true, therefore also a paradox! *the frog and the gold could literally be in either box and it wouldn't change the truth value, since having a box have both things has been ruled out as a possibility by the jester and ironically, even that one with only one condition being true is only met with a paradoxical truth value!* (no wonder the king imprisoned them) in the later riddle the key has just been put into a box that therefore has become paradoxical in the truthfulness of its statement, since it referred to itself. one could've figured out that it was there if one considered what both possibilities of where the key and dagger are and where someone who intends for you to pick the wrong option would put things into,

Uhhhhh, my solution is that i pick the jester..... Up, then play a rook and a +2 which i rotate sideways then i only have 5 pieces, so i roll for wisdom with a -84 modifier from the stunned status effect which flips to +20 and blackjack! And now everyone is too puzzled to do anything, i steal the frog and run away never to be seen again. (Which doesn't mean i won't return.)

The voice actor for the Jester Krystle Futrell, sounds kind of like Colleen O'Shaughnessey who voices Tails in sonic boom. Neat :D