Denny VrandečićMay 20

"Maria and Peter are students and meet up for a late dinner. Peter asks Maria whether Tom is at the party that they intend to go to after dinner. Maria answers that Tom is at the party. After all, Tom had told her that he would be at the party. When they arrive at the party, it turns out that Tom had changed his plans, and is not at the party. Was Maria's answer true or false?"

#truth #philosophy #cognition

(please spread for visibility, I would like this to be as wide as possible)

1/2

Maria's answer was true
32.6%
Maria's answer was false
67.4%
Poll ended at .
Show threadDenny Vrandečić

A new study shows that there is much, much less agreement on the answer to this question than I would have expected. Even after reading about the study, I still expect people in my bubble to have the same answer as I do. Let's see. But this probably means that the meaning of truth, in the general population, is simply different from what I would have assumed. And explains a number of public discourses.

2/2

https://reason.com/2026/05/15/the-surprising-divide-over-what-counts-as-true/

New study investigates why people disagree about what's true

A new study finds that what people think about facts, authenticity, or coherent beliefs explains why they disagree about what is true.

Reason.com
May 20 at 3:51pmWeb
Show threadjanjkoMay 20
@vrandecic so some people equate someone lying to someone's statement being false? Then they should have a different word for someone being unintentionally wrong?
Show threadDenny VrandečićMay 20
@janjko yeah, I have the same problem. I would say Maria never lied. But for me, that doesn't mean what she said is true.
Show threadRob van Kan🔻May 20
@vrandecic @janjko as far as she knew, it was true.
Show thread\u1f0a1May 20
@edgeofeurope @vrandecic @janjko No, she had no way of knowing it was true.
Show threadkæt6d ago

@bnlandor @edgeofeurope @vrandecic @janjko We can never be absolutely certain of anything at the level of logic.

This seems mainly to be a problem about the practice assigning logical truth values to real life language acts.

It seems we can all agree on the practical meaning, consequences, and so on, and whether the different parts of the bundle of things we might mean by a statement being true are satisfied and what they might be contingent on (the personalities of the people, their circumstance, etc)..

Where we disagree seems to be on this truth-value labelling pursuit which, a bit like village cricket, I'm pleased some people are passionate about, but I'm not sure I'm one of them.

Show threadbor[x]a 🇵🇸 ボルシャ 2d ago
@chiffchaff well, modality exists @bnlandor @edgeofeurope @vrandecic @janjko
Show threadkæt2d ago
@protoeuskaldun @bnlandor @edgeofeurope @vrandecic @janjko Dunnocks much more so.
Show threadbor[x]a 🇵🇸 ボルシャ 2d ago
@chiffchaff LOL, sorry for my brief reply; what I meant was that the question posed at the start has a clear logical answer for me, as Maria could have used some form of modal or evidential marker. By not doing so, even if she wasn’t lying intentionally, her statement lends itself to a fairly straightforward assessment of falsity. @bnlandor @edgeofeurope @vrandecic @janjko
Show threadkæt2d ago

@protoeuskaldun @bnlandor @edgeofeurope @vrandecic @janjko sorry, I thought you were making a claim for the foundational importance of truth values of utterances in building a model of the world.

Maria could have been clearer about her level of knowledge, to make the surface meaning match the pragmatic purpose, but that can be a tedious fool's errand if you go too far with it in real life.

Show threadDaniel Gibson1d ago

@chiffchaff @protoeuskaldun @bnlandor @edgeofeurope @vrandecic @janjko
At what point could she be 100% sure anyway? Even if he had told her earlier that he was at the party he could've left by then...
If she knew him to be chained to the wall at that party? Even then he might have died by now, which opens another can of worms about the definition of *being* at the party :-p

It's obvious that she could only answer with what she knew at the time and that a "yes" implies "as far as I know"

Show threadkæt1d ago
@Doomed_Daniel @protoeuskaldun @bnlandor @edgeofeurope @vrandecic @janjko it could be an alien hologram of him, or she could be afflicted by psychosis, or whatever. I think it's okay to say false things by accident when the world is conspiring against you, but here, as long as the questioner had a fair understanding of the answerers level of knowledge, I think "is" is just a placeholder for a complex construction already understood by context by both parties. If I ask "Is there a film at 11?" at 9, I think I can say yes truthfully, without saying "as long as there isn't a major international incident in the next two hours. That "is" is clearly about scheduling.
Show threadEvelyn Estelle1h ago

@chiffchaff @Doomed_Daniel @protoeuskaldun @bnlandor @edgeofeurope @vrandecic @janjko

Or you can just cut out all the uncertainty and assumption and say "he said he will be at the party" or "yes, the film is scheduled at 11".

Show threadHiker Geek 🌲💻🌲4d ago

@bnlandor @edgeofeurope @vrandecic @janjko

I think she can be pretty sure that it's true Tom told her he would be at the party.

What Tom said to her wasn't true.

Show threadMelvin Gundlach4d ago
@HikerGeek @bnlandor @edgeofeurope @vrandecic @janjko Yes, but that wasn’t the question. If the question was if Tom *said* he would be at the party, then yes. As it is written, Maria’s statement is false (even though not an intentional lie).
Show threadtessarakt4d ago
@bnlandor @edgeofeurope @vrandecic @janjko Which Peter knew. So his question must be understood as being about her belief according to the information available to her.
Show threadSiderea, Sibylla Bostoniensis1d ago

@tessarakt

No, that logically does not follow. By normal convention all requests for information are accompanied by the implicit qualifier, "if you know".

This is precisely why LLMs never answering "I don't know" and instead hallucinating an answer is such a violation of the social compact.

@bnlandor @edgeofeurope @vrandecic @janjko

Show thread\u1f0a11d ago
@siderea @tessarakt @edgeofeurope @vrandecic @janjko Does that affect the truth value of her statement in any way? Not any potentially implied statement, but the actual statement.
Show threadSiderea, Sibylla Bostoniensis1d ago

@bnlandor
Of course. Allow me to demonstrate.

Imagine that you say to Maria, "Oh, hey, I see there's a party at Jane's place. Is Tom at the party?" and Maria, knowing perfectly well that Tom is not at Jane's party but Susie's party across town, and not wanting you to know that, deliberately trades on ambiguity to deceive by saying, "Yes, Tom is at the party." Further imagine that you subsequently find out that Tom was not at Jane's party but at Susie's party, and Maria knew that, and you confront Maria, "Hey! Why did you tell me that Tom was at Jane's party when you knew he was at Susie's party?"

Imagine that Maria replies, "I did no such thing. I didn't tell you that Tom was at Jane's party. I said he was at *the* party."

This would be pretty universally agreed to be a specious argument.

This is because the truth or falsity of an answer to a question is only determinable in the context of the question it is answering.

So it turns out to matter pretty enormously to the truth or falsity of Maria's answer to Peter just which question she was answering when she uttered it.

@tessarakt @edgeofeurope @vrandecic @janjko

Show threadtessarakt1d ago

@siderea @bnlandor @edgeofeurope @vrandecic @janjko "This would be pretty universally agreed to be a specious argument."

However, the US Supreme Court might consider it literally true under the Bronston literal truth defense. https://en.wikipedia.org/wiki/Bronston_v._United_States

Bronston v. United States - Wikipedia

Show threadOrman1d ago
@siderea @tessarakt @bnlandor @edgeofeurope @vrandecic @janjko I don't see the comparison to an LLM. LLMs are expected to say "I don't know" and fail to when they produce answers they have no basis for in either direction. Maria did have (very strong) basis for her answer, even though it happened to be wrong.
Show threadSiderea, Sibylla Bostoniensis1d ago

@orman Depends on what you mean by "expected". A lot of people expect LLMs to say "I don't know" and notoriously LLMs rarely if ever say "I don't know" and this is this a violation of that expectation if you have it.

@tessarakt @bnlandor @edgeofeurope @vrandecic @janjko

Show threadJeff Grigg1d ago

@siderea @orman @tessarakt @bnlandor @edgeofeurope @vrandecic @janjko

Expecting LLMs to say "I don't know." is an unreasonable expectation. That's not what they're built to do. And LLMs don't actually "know" anything, in any strict logical "thinking" sense. They're designed to produce plausible sequences of text. The truth or falsity of their statements is irrelevant. If fed text of many humans lying, as training input, the LLM will do the same, without regret or even "thought."

Show threadSarah Peper 🏳️‍⚧️🇺🇦1d ago
@bnlandor @edgeofeurope @vrandecic @janjko but this is the default. I automatically parse her statement as "I believe he will be there", because the actual fact is unknowable at that point. We just use shortcuts to not use "to the best of my knowledge" in every sentence we say
Show threadPomegranate_StewMay 20

@vrandecic @janjko

I agree. What she should have said is that he said he would be at the party. Then it wouldn’t be false either way.

Show threadFoolishOwl6d ago
@pomegranate_stew @vrandecic @janjko I find people often express frustration when I use conditional statements, but I find it frustrating that it's apparently a social norm to express unwarranted certainty.
Show threadMorgan ⚧️6d ago

@vrandecic @janjko this. What she said was not true, and I don't understand* how that can be controversial because it was factually incorrect. That doesn't mean she was lying, it just means she was wrong

*I understand better after reading the article but it still boggles my mind

Show threadKaspi4d ago
@raphaelmorgan If Tom was at the party at the time Maria answered the question (which she would not have been aware of either) but had left before the others arrived, would that change your view on this?
Show threadMorgan ⚧️4d ago
@kaspi yes, then she'd be telling the truth (No more effectively than an LLM, one could argue, because she doesn't actually know the truth and is just supplying her best guess as if she does know). I was going off of the original prompt that said "Tom had changed his plans," suggesting he never went, but if he simply left before they got there that's another story
Show threadKaspi4d ago
@raphaelmorgan The issue I see with the original example is that it uses a social situation as backdrop. In which one would normally assume conversational norms and phrases. According to Grice's maxim of quality https://en.wikipedia.org/wiki/Cooperative_principle#Grice's_maxims Marie told the truth. A reader of the story could assume that the question was not asked by an external observer (asking for general facts) but by Peter within the situation's context, thus asking what Maria knows about Tom's plans. Everything else would be silly.
Cooperative principle - Wikipedia

Show threadKaspi4d ago

@raphaelmorgan As someone within the system you are talking about, you can only make true statements about things you can validate/observe at the time you make your statement. Everything else would be assumptions or speculation, even if most of these often turn out correct, because the system is rather stable. We are basically talking about cats in boxes here.

Expecting only 100% true statements at any time would make normal conversations nearly impossible.

Show threadKaspi4d ago

@raphaelmorgan So my personal opinion is that the researchers should have phrased their question more clearly and made it obvious, that they were looking for objective facts and not an interpretation of Maria's situational response.

My own experience tells me, that when people ask questions about stories (e.g. like book discussions in school), they want to know what the writer and characters in said story did/want to express.

Is there even a clear definition of truth?

Show threadMorgan ⚧️4d ago
@kaspi there isn't a clear definition of truth, at least according to the article. I thought there was prior to reading it, but evidently only about half of people in the study think truth means what I think it means, so I guess it's not that clear 😂
Show threadGin Kangaroo6d ago
@vrandecic @janjko Yes. Is this not a common interpretation?
A false statement in good faith doesn't fall into the same category as lying, for me. Maria did make her statement too definitive based on, essentially, hearsay. But not exactly a lie.
I would have replied, as far as I know, yes.
Show threadIgnazio Palmisano6d ago

@GinevraCat @vrandecic @janjko I'd say she makes her statement on more than hearsay. Tom said he'd be at the party. Unless Tom had a track record of changing his mind or lying, she had enough information to expect him to be there.

Now, if Peter was an attorney about to start questioning a witness, she might want to be more explicit, but she was having dinner before a party...

Show threadGin Kangaroo6d ago
@ignaziop1977 @vrandecic @janjko Fair.
Show threadJeff Grigg1d ago

@ignaziop1977 @GinevraCat @vrandecic @janjko

Yes. In the most strict logical interpretation, Mary has no way of knowing if anyone will be at the planned party. There might have been a gas explosion or plane crash or terrorist attack that destroyed the entire party location.

But unless Mary had reason to believe that Tom "changes his plans" about going to parties, she has reasonable reason to believe what Tom told her. So she did not *lie*.

Show threadJeff Grigg1d ago

@ignaziop1977 @GinevraCat @vrandecic @janjko

I could "split hairs" a little and say that Mary probably does not have good reason to believe that Tom *is* at the party *right now*, as he may be having dinner elsewhere right now, and will be showing up "late," as they are.

But this is a casual social conversation where "is" and "will be" and "probably" and "to the best of my knowledge" should generally be assumed.

Show threadSiderea, Sibylla Bostoniensis2d ago

@vrandecic @janjko

There's a valid argument that Maria lied by implication: by answering "he is there", she was also implying "I know that he is there", and that was a willful or irresponsible misrepresentation of how much knowledge she had of the situation.

So she wasn't lying about whether or not he was there. But she was, arguably, lying by implication that she was in a position to say whether or not he was there, which she wasn't.

Show threadEvelyn Estelle56m ago

@siderea @vrandecic @janjko

This is a really good point, and it puts into words my gut feeling about the matter.

Show threadmeeoo1d ago
@vrandecic @janjko I do remember reading something somewhere (well that's helpful) about conceptions of lying across cultures where in some places Maria's statements, even though she was not purposely stating a falsehood, would be considered lying
Show threadTattie1d ago
@vrandecic yes, it was a justified belief, but not a true one
@janjko
Show threadIrinaMay 20
@janjko @vrandecic Her answer was false but she wasn't lying; she was simply wrong. It's only lying when you knowingly make a false statement.
Show threadDenny VrandečićMay 20
@irina @janjko That's also how I understand the terms.
Show threadJakob VoßMay 20
@vrandecic @irina @janjko if Maria had said yes or no without knowing about Tom, this would neither have been a lie, but bullshit.
Show threadBrad RosenheimMay 20

@nichtich
Bullshit does indeed have a formal philosophical definition that seems to work here. https://philosophywithoutbullshit.com/2026/04/20/what-the-hell-bullshit-is-revising-frankfurts-definition/

@vrandecic @irina @janjko

What the Hell Bullshit Is: Revising Frankfurt’s Definition

Difficulty: What the hell In his work On Bullshit, Harry Frankfurt famously defined bullshit as, roughly, a product of a speaker who is indifferent to the truth. Note that bullshitting is different…

Philosophy without Bullshit
Show threadRodrigo SantamaríaMay 20
@vrandecic @irina @janjko that's how it is. The fact that it seems debatable is the symptom of so many things
Show threadBen Aveling6d ago
If you claim something is true when you know that you don’t know if it is true or not, then that’s a lie, even if it turns out to be true. @vrandecic @irina @janjko
Show threadIrina6d ago
@BenAveling @vrandecic @janjko Yes; you need to qualify it with "I think X" or "I'm practically sure that X"
Show threadBrooke Vibber May 20

@vrandecic (not having read the link) it's a question about something that could happen in the future. Therefore it's impossible for the statement to *really* be either true or false; it's a prediction based on past information; I'd say the statement is true -- that is her prediction based on previously obtained information and she's not saying anything false about what she predicts -- and whether the prediction turns out to be correct is a separate question that is not asked in the poll.

(Update) Read the link and now more confirmed that claiming Maria's statement is false is mumbo jumbo in this case. Y'all are asking the wrong question for the context, so you get a nonsensical answer.

Show threadJohn-Mark GurneyMay 20

@brooke
Yeah, anyone who, when asked about someone if they're at the party, doesn't respond with something like "they're supposed to be but I haven't seen them yet", but a statement "yes they're here" is a crazy liar. They can't be trusted about anything factual. They are willing to state as fact information that they don't have knowledge of.

@vrandecic

Show threadRoberto von Archimboldi6d ago

@brooke @vrandecic you can make true statements about the future. You can even know things about the future. 'I will be alive in 15s' is true now. I know it. Some future facts, like that one, are more knowable than past facts. I doubt that anyone could ever know if it rained on this exact spot, as defined by its polar co-ordinates, on this day 3200 years ago. I am on the South coast of England. The weather is changeable and the climate has not changed that much in 3000 years.

It seems to me that the real confusion here is not between lying and making a false statement. I think that is a puzzle about knowledge. Assuming Tom is normally reliable, you might think that if Tom had gone to the party, not only would Maria's claim have been true, she would have known it to be true. It is odd that she didn't know it simply because Tom was not his usual reliable self.

My guess is that what drives people to conclude that Maria's claim was true is that they are aware that if you know that p, then it is true that p. You can't know something that is false. If you also think that Maria knew that Tom was going to the party when she told her friend that, then you have to think that her claim was true.

It is that puzzle which people are grappling with. I'm not sure how to solve it. It is too quick to say that there is no knowledge about the future or that there are no future facts. There is something about knowledge that sets it apart from true belief and it is not that true belief is any less efficient for getting things done. It feels like there is something reliable about knowledge that makes it valuable. That feels like it something that the knower should have access to. If so, it seems like Maria can't ever know that reliable Tom will be at the party. It also feels like she can. If we can't know things about the future, how can we organise our lives?

(Plato sets up this puzzle with his road to Larissa. Why, he is asks, is it better to know that this is the right road instead of merely believing truly? Both mental states will get you to Larissa).

Show threadBob Blaskiewicz 🇺🇦 🇨🇦 🇬🇱May 20
@vrandecic Seems like a false (true?) dichotomy: true, false, uninformed/incomplete
Show threadMorgan ⚧️6d ago
@rjblaskiewicz @vrandecic it is uninformed, but it's still false. He was objectively not there.
Show threadBob Blaskiewicz 🇺🇦 🇨🇦 🇬🇱6d ago
@raphaelmorgan @vrandecic True. :)
Show threadBob Blaskiewicz 🇺🇦 🇨🇦 🇬🇱6d ago

@raphaelmorgan @vrandecic

This last semester, my students and I were reading about the psychology behind "the dress" and one of the articles noted the dozens of processes that take place before you become aware of the color. The idea was that it's not even a decision. The brains of people who worked outside saw it one way and those whose brains compensated for artificial light saw it another way. Baseline understanding of concepts are similarly filtered, apparently....

Show threadBob Blaskiewicz 🇺🇦 🇨🇦 🇬🇱6d ago

@raphaelmorgan @vrandecic

So, following from that, there are a lot of notions, ideas, and predispositions that filter what gets assigned the feeling of "obviously and inarguably true." That said, I am inclined to agree with you. :)

Show threadMorgan ⚧️4d ago
@rjblaskiewicz @vrandecic if I found out (I think I did at one point and forgot) what colors the dress actually were, I would still say that the picture appears the other set (when it does--my perception of it wasn't consistent), but the dress itself still would not be those colors. The example doesn't quite fit though imo, because colors are more subjective than "is X at Y". If I was asked if the dress was at least partially in the picture, any argument that it's not would confuse me.
Show threadBob Blaskiewicz 🇺🇦 🇨🇦 🇬🇱4d ago

@raphaelmorgan @vrandecic

I getcha. :)

Show threadThomas HodgsonMay 20
@vrandecic I noticed that some people interpret Maria's claim as a claim about what will happen in the future. I wonder if that affected the results? (I think that there is some evidence that some people take claims about what will happen to be true if they would become true if things carried on as they are now.)
Show threadBradalot “”6d ago

@vrandecic

When a religious Christian understands “I am the way, the truth, and the life. No one comes to the Father except through me.” they are not thinking about boolean logic.

It does not escape me that the percentage of U.S. and British respondents in the survey reviewed by Reason, who report coherence and authenticity as determinants of truth (rather than correspondence), roughly matches the percentage of U.S. and British who consider themselves religious.

It also probably is not neutral to such a respondent that the interlocutors in the example are named Mary and Peter.

New study investigates why people disagree about what's true

A new study finds that what people think about facts, authenticity, or coherent beliefs explains why they disagree about what is true.

Reason.com