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I'm highly sympathetic to the intuition that the liar sentence is devoid of meaning in some important respect, but I don't think we can just declare the liar sentence meaningless and then call it a day. Because in another respect, it definitely seems meaningful. I understand what a sentence is, and I feel like I understand what it is for a sentence to be true or false. If someone wrote on a blackboard "The thing written on the blackboard of room 428 is false," I feel like I would understand what this is saying before I went to check out room 428. Hence I must understand the sentence if it turns out that we're in room 428 already.

Also consider the Strengthened Liar: "This sentence is not true." According to your solution, that sentence should also be dismissed as meaningless, right? But surely meaningless sentences a fortiori aren't true. But that's precisely what the sentence asserts, hence it is true.

I remember being bothered by this problem, and feeling like I had resolved it as an undergrad. Calling it a "true contradiction" seems absurd; you've just drawn a circle around it and said, "Nothing to see here! Move along!"

I think the solution is related to modal logic. "This sentence is false" creates a self-referential universe devoid of meaning, and thus has no truth value. It refers only to the world of itself, and there are no rules that it can be evaluated against, nor are there any observations that can confirm or disconfirm it. It is, in a sense, epiphenomenal, as there is no actual thing which it corresponds, predicts, or relates to. It is, in a sense, a one-sentence universe that cannot be tied to anything in any other universe.

This concept seems more robust in my mind; I suspect I am either making a mistake or failing to explain myself. Criticism or questions would be appreciated.

It would be helpful to know more about the sorts of things they typically post about, but I understand you probably don't want to inadvertently reveal the smart-wrong individuals you have in mind.

The reason I say this is because there are probably a lot of people out there like me - people who, while liking the LessWrong community and its stewards overall, have some serious bones to pick with some of the "core" "rationalist" beliefs and approaches to various questions. These two things in combination beget an urge to respectfully but persistently voice disagreement with things most others here take as received wisdom. I haven't ever really posted here, for instance, but if I did, I know that I would mainly only do so when I disagreed with something I felt most people here took to be obvious. Or, to put a more positive spin on it, I would only post when I stood an unusually high chance of being corrected-if-wrong. Since the opinions of mine that stand the best chance of this here are those that are far out of line with the beliefs of the average LessWrong user, it follows that if your stance is sufficiently close to that of the average LWer, most of what I'd post you'd disagree with.

Of course, I may not count, because I may not be smart! And you may deviate greatly from the average. But in that case, it should be pretty obvious why you find smart people you persistently disagree with on this site.

(NB: I put the quotes around the word "rationalist" not to cast aspersions on its use by people here, but because I wouldn't consider myself an LW-style rationalist despite being someone who cares deeply about thinking rationally. Kind of like how an agnostic might opt out of calling atheists "brights" on account of not being an atheist while still considering himself bright.)

Man, this just makes the fanfic-as-idealized-autobiography bells go off in my head even more.

(Also, I totally sympathize on the most-upvoted sadness.)

Harry has decided, I'm sure correctly, that Quirrell's ability to flawlessly adopt any persona and simulate any intention for long stretches of time while simultaneously furthering his own (true) goals makes him impossible to trust. But if Harry buys into Quirrell's claims, Harry is equally capable of perpetual, undetectable duplicity and therefore equally unworthy of trust. And if he believes that's the case, it's just going to isolate him further, since he'll conclude that anyone who wants to be his friend is either irrational or overlooking the factors that make him an untrustworthy person. So Quirrell may have just convinced Harry that literally all of his relationships, present or future, are tantamount to a sort of deception. Good job!

I feel almost certain that Harry is living in a computer simulation. I know he ruled it out because he decided the existence of the Time Turner renders the universe non-computable, but how can he be sure that he's actually going backwards in time instead of the universe "simulating going back to the past and computing a different future?"

Hi, I'm also interested. I don't know if I've very much to contribute compared to some other folks, but hopefully I could still tag along?