trentmkelly/LessWrong-43k huggingface dataset:
Very Basic Model Theory
by So8res — 2013-10-31T07:06:56.951Z

In this post I'll discuss some basic results of model theory. It may be helpful to read through my previous post if you haven't yet. Model Theory is an implicit context for the Heavily Advanced Epistemology sequence and for a few of the recent MIRI papers, so casual readers may find this brief introduction useful. And who knows, maybe it will pique your interest:

A tale of two logics

propositional logic is the "easy logic", built from basic symbols and the connectives "and" and "not". Remember that all other connectives can be built from these two: With Enough NAND Gates You Can Rule The World and all that. Propositional logic is sometimes called the "sentential logic", because it's not like any other logics are "of or relating to sentences" (/sarcasm).

first order logic is the "nice logic". It has quantifiers ("there exists", "for all") and an internal notion of equality. Its sentences contain constants, functions, and relations. This lets you say lots of cool stuff that you can't say in propositional logic. First order logic turns out to be quite friendly (as we'll see below). However, it's not strong enough to talk about certain crazy/contrived ideas that humans cook up (such as "the numbers").

There are many other logics available (second order logic AKA "the heavy guns", ω-logic AKA "please just please can I talk about numbers", and many more). In this post we'll focus on propositional and first-order logics.

Training Wheels

As a warm-up, let's define "models" for propositional logic.

Remember, logics together with languages produce sentences. Languages of propositional logic are sets of basic symbols. From these symbols and the two connectives of propositional logic (∧ and ¬) we construct our sentences.

For example, from the language {x, y} we can build the sentences x, ¬x, x∧y, and many more. We cannot build sentences like hello (which doesn't use the right symbols) or ¬xy (which breaks the rules of the logic).

We want to study interpretations for such sentences, where an "interpretation" is some object which assigns a truth value to each sentence. This is denoted by the ⊧ operator: A⊧B expresses some form of "A models B as true". This operator is used frequently and in many contexts throughout model theory.

What we're looking for is some object (set) such that there is a relation (⊧) between the object and all sentences generated ...
Human Memory: Problem Set
by LoganStrohl — 2013-10-31T04:08:45.436Z

I'm working on a post about how best to use human memory—when it's good to store things in your own brain and why, when it's best to outsource your memory, what memory upgrades are worthwhile in what contexts, and how to integrate and apply memory systems in real life. I'm hoping the following set of memory problems will draw out approaches that haven't occurred to me so I can compare a wider range of methods.

I'll post the first solutions I thought of myself later on, but for now I'd like to hear what you would do in each of these situations and what you believe to be the pros and cons of your answers. Can you think of ways to improve upon your first thoughts and the answers of others?

(You don't have to respond to all of the questions; feel free to post as little or as much as comes to mind.)

1. I'm leaving for a week-long business trip. The last time this happened, I wasn't totally sure I'd remembered to lock my door. The worry wouldn't leave my mind and was making it hard to relax, so I eventually called a friend and asked them to stop by and make sure it was locked. Now, I'm standing in front of my door, suitcase in hand, all ready to go, and I'm about to lock it. What should I do?

2. I'm in the middle of a conversation with a friend. He mentions a book that really interests me. It's called Antifragile and I think, "I've got to remember to Google that." But the conversation continues, and it would be rude to pull out my phone right this minute.

3. I bought a new fridge. This one closes differently than my old fridge: My old fridge would swing shut and seal nicely if I just left it open, while this one requires that I push on the door even when it's mostly closed to ensure it seals. For some reason, I'm having a hard time with this transition. I've had it for a week, and I've come home from work to find my more perishable food spoiled three times already. It's not that there's a problem with the latching mechanism or that the seal is bad. The problem is that I keep forgetting.

4. I'm driving in an unfamiliar city. My GPS says my destination is somewhere around here, but I suspect it's working with slightly outdated information. Rather than driving around aimlessly in hopes that I'll randomly run across that which I seek, I sensibly stop to ask a local for directions. Unfortunately, it seems that the business I'm looking for has moved to another...
Aliveness in Training
by katydee — 2013-10-31T01:17:20.995Z

Related: The Martial Art of Rationality

One principle in the martial arts is that arts that are practiced with aliveness tend to be more effective.

"Aliveness" in this case refers to a set of training principles focused on simulating conditions in an actual fight as closely as possible in training. Rather than train techniques in a vacuum or against a compliant opponent, alive training focuses on training with movement, timing, and energy under conditions that approximate those where the techniques will actually be used.[1]

A good example of training that isn't alive would be methods that focused entirely on practicing kata and forms without making contact with other practitioners; a good example of training that is alive would be methods that focused on verifying the efficacy of techniques through full-contact engagement with other practitioners.

Aliveness tends to create an environment free from epistemic viciousness-- if your technique doesn't work, you'll know because you won't be able to use it against an opponent. Further, if your technique does work, you'll know that it works because you will have applied it against people trying to prevent you from doing so, and the added confidence will help you better apply that technique when you need it.

Evidence from martial arts competitions indicates that those who practice with aliveness are more effective than others. One of the chief reasons that Brazilian jiu-jitsu (BJJ) practitioners were so successful in early mixed martial arts tournaments was that BJJ-- a martial art that relies primarily on grappling and the use of submission holds and locks to defeat the opponent-- can be trained safely with almost complete aliveness, whereas many other martial arts cannot.[2]

Now, this is not to say that one should only attempt to practice martial arts under completely realistic conditions. For instance, no martial arts school that I am aware of randomly ambushes or attempts to mug its students on the streets outside of class in order to test how they would respond under truly realistic conditions.[3]

Even in the age of sword duels, people would train with blunt weapons and protective armor rather than sharp weapons and ordinary clothes. Would training with sharp weapons and ordinary clothes be more alive than training with blunt weapons and protective armor? Certainly, but the trainees wouldn't be! And yet training with b...
I need some help debugging my approach to informal models and reasoning
by Arkanj3l — 2013-10-30T22:10:45.071Z

I'm having trouble understanding the process I should use when I am considering new models as they might apply to old data, like memories. This is primarily when reasoning with respect to qualitative models, like those that come out of development psychology, business, or military strategy. These models can be either normative or descriptive, but the big trait that they all seem to share is that they were all conceptualized with reference to the inside view more than the outside view - they were based on either memories or intuition, so they will have a lot of implicit internal structure, or they will have a lot of bullshit. Re-framing my own experiences as a way of finding out whether these models are useful is thus reliant on system one more than system two. Unfortunately now we're in the realm of bias.
My concrete examples of models that I am evaluating are (a) when I am attempting to digest the information contained in the "Principles" document (as discussed here) and for which situations the information might apply in; (b) learning Alfred Adler's "individual psychology" from The Rawness, which also expands the ideas and (c) the mighty OODA loop.
When I brought up the OODA loop during a meetup with the Vancouver Rationalists I ended up making some mistakes regarding the "theories" from which it was derived, adding the idea of "clout" to my mental toolkit. But it also makes me wary that my instinctive approach to learning about qualitative models such as this might have other weaknesses.
I asked at another meetup, "What is the best way to internalize advice from books?" and someone responded with thinking about concrete situations where the idea might have been useful.
As a strategy to evaluate the truth of a model I can see this backfiring. Due to the reliance on System One in both model structuring and model evaluation, hindsight bias is likely to be an issue, or a form of Forer effect. I could then make erroneous judgements on how effectively the model will predict an outcome, and use the model in ineffective ways (ironically this is brought up by the author on The Rawness). In most cases I believe that this is better than nothing, but I don't think it's good enough either. It does seem possible to be mindful of the actual conceptual points and just wait for relevance, but the reason why we reflect is so that we are primed to see certain patterns ag...
Why officers vs. enlisted?
by JoshuaFox — 2013-10-30T20:14:52.156Z

It's always puzzled me that, in armies, officers form a separate hierarchical ladder from the NCOs and enlisted soldiers.

Armies could have a single hierarchy, top to bottom, as in the simplified diagram below on the left. Instead, all armies have two distinct ladders, with one strictly above the other, as on the right. (Reminds me of those wacky non-standard integers.)

The usual answers are obvious but irrelevant: Yes, some people shoot straight to a position high on the ladder. You could do that with either model. Yes, even when those lower down on the ladder have more experience and wisdom, it can make practical sense to have a hierarchy. Yes, the higher someone is, the higher the level of the decisions they make. You could likewise do these on a one-ladder model.

It's said that officers "decide," while non-officers "just carry out orders"; or that officers choose strategy, and non-officers do tactics. But everyone makes decisions, on their own level. A private makes decisions for himself, a corporal for three soldiers, and a colonel for a thousand, each one in the context of their orders from above. One soldier's strategy is his superior's tactics. And the distinction is not based on command: New army doctors automatically become officers, even if they don't command anyone. Doctors are non-combatants, but fighter pilots are combatants par excellence, don't command anyone, and are all officers.

These answers don't explain why there need to be two ladders. I asked at Quora without a convincing answer. Historically, the distinction was based on social classes, but that doesn't explain why every army follows this arrangement, including those in very different societies.

Similarly: What's a corporate executive? (I'm talking about large companies here; small companies and startups are different.) I understand that there is a management hierarchy, but why the arbitrary distinction between a senior manager and a junior executive? Aren't those just two rungs on the ladder? In corporate-speak, an executive is called a "decision maker." What a strange term! Isn't a manager or even a lowly "individual contributor" also a decision maker -- at the scope that their own managers allow? (I should add that the two-ladder system is not as developed in business as it is in...
Meetup : Washington DC/VA Games meetup
by rocurley — 2013-10-30T18:37:48.529Z

Discussion article for the meetup : Washington DC/VA Games meetup

WHEN:
03 November 2013 03:00:00PM (-0400)

WHERE:
6305 Windward Dr., Burke VA 22015, 703-239-9660.

(The time should read 3:00 pm: there's been some weirdness with the display).

We'll be meeting to hang out and play games. The meetup is at a house and not directly metro accessible, so there will be a van to pick people up from Franconia-Springfield metro at 2:55 pm. If you need a ride from the metro and suspect you will be unable to make the pickup time, please message me or maia and let us know ASAP.

Discussion article for the meetup : Washington DC/VA Games meetup
Meetup : Durham/RTLW HPMoR discussion, chapters 94-96
by therufs — 2013-10-30T17:44:33.128Z

Discussion article for the meetup : Durham/RTLW HPMoR discussion, chapters 94-96

WHEN:
02 November 2013 12:00:00PM (-0400)

WHERE:
726 Rigsbee Avenue, Durham, NC 27701

Bring a question, an observation, or any other thing you might like to discuss from chapters 94-96 of HPMoR.

We'll gather coffee around noon and have discussion 12:30-2ish.

Hope to see you there!

Discussion article for the meetup : Durham/RTLW HPMoR discussion, chapters 94-96
Democracy and rationality
by homunq — 2013-10-30T12:07:24.727Z

Note: This is a draft; so far, about the first half is complete. I'm posting it to Discussion for now; when it's finished, I'll move it to Main. In the mean time, I'd appreciate comments, including suggestions on style and/or format. In particular, if you think I should(n't) try to post this as a sequence of separate sections, let me know.

Summary: You want to find the truth? You want to win? You're gonna have to learn the right way to vote. Plurality voting sucks; better voting systems are built from the blocks of approval, medians (Bucklin cutoffs), delegation, and pairwise opposition. I'm working to promote these systems and I want your help.

Contents: 1. Overblown¹ rhetorical setup ... 2. Condorcet's ideals and Arrow's problem ... 3. Further issues for politics ... 4. Rating versus ranking; a solution? ... 5. Delegation and SODA ... 6. Criteria and pathologies ... 7. Representation, Proportional representation, and Sortition ... 8. What I'm doing about it and what you can ... 9. Conclusions and future directions ... 10. Appendix: voting systems table ... 11. Footnotes

1.

This is a website focused on becoming more rational. But that can't just mean getting a black belt in individual epistemic rationality. In a situation where you're not the one making the decision, that black belt is just a recipe for frustration.

Of course, there's also plenty of content here about how to interact rationally; how to argue for truth, including both hacking yourself to give in when you're wrong and hacking others to give in when they are. You can learn plenty here about Aumann's Agreement Theorem on how two rational Bayesians should never knowingly disagree.

But "two rational Bayesians" isn't a whole lot better as a model for society than "one rational Bayesian". Aspiring to be rational is well and good, but the Socratic ideal of a world tied together by two-person dialogue alone is as unrealistic as the sociopath's ideal of a world where their own voice rules alone. Society needs structures for more than two people to interact. And just as we need techniques for checking irrationality in one- and two-person contexts, we need them, perhaps all the more, in multi-person contexts.

Most of the basic individual and dialogical rationality techniques carry over. Things like noticing when you are confused, or making your opponent's arguments into a s...
Mental Context for Model Theory
by So8res — 2013-10-30T06:35:32.743Z

I'm reviewing the books on the MIRI course list. After my first four book reviews I took a week off, followed up on some dangling questions, and upkept other side projects. Then I dove into Model Theory, by Chang and Keisler.

It has been three weeks. I have gained a decent foundation in model theory (by my own assessment), but I have not come close to completing the textbook. There are a number of other topics I want to touch upon before December, so I'm putting Model Theory aside for now. I'll be revisiting it in either January or March to finish the job.

In the meantime, I do not have a complete book review for you. Instead, this is the first of three posts on my experience with model theory thus far.

This post will give you some framing and context for model theory. I had to hop a number of conceptual hurdles before model theory started making sense — this post will contain some pointers that I wish I'd had three weeks ago. These tips and realizations are somewhat general to learning any logic or math; hopefully some of you will find them useful.

Shortly, I'll post a summary of what I've learned so far. For the casual reader, this may help demystify some heavily advanced parts of the Heavily Advanced Epistemology sequence (if you find it mysterious), and it may shed some light on some of the recent MIRI papers. On a personal note, there's a lot I want to write down & solidify before moving on.

In follow-up post, I'll discuss my experience struggling to learn something difficult on my own — model theory has required significantly more cognitive effort than did the previous textbooks.

Between what was meant and what was said

Model theory is an abstract branch of mathematical logic, which itself is already too abstract for most. So allow me to motivate model theory a bit.

At its core, model theory is the study of what you said, as opposed to what you meant. To give some intuition for this, I'll re-tell an overtold story about an ancient branch of math.

In olden times, Euclid built Geometry upon five axioms:

You can draw a straight line segment between two points.

You can extend line segments into infinitely straight lines.

You can draw a circle from a straight line segment, with the center at one end and radius the line segment.

All right angles are congruent.

If two lines are drawn which intersect a third in such a way that the sum

...
Bayesianism for Humans
by ChrisHallquist — 2013-10-29T23:54:14.890Z

Recently, I completed my first systematic read-through of the sequences. One of the biggest effects this had on me was considerably warming my attitude towards Bayesianism. Not long ago, if you'd asked me my opinion of Bayesianism, I'd probably have said something like, "Bayes' theorem is all well and good when you know what numbers to plug in, but all too often you don't."

Now I realize that that objection is based on a misunderstanding of Bayesianism, or at least Bayesianism-as-advocated-by-Eliezer-Yudkowsky. "When (Not) To Use Probabilities" is all about this issue, but a cleaner expression of Eliezer's true view may be this quote from "Beautiful Probability":

No, you can't always do the exact Bayesian calculation for a problem. Sometimes you must seek an approximation; often, indeed. This doesn't mean that probability theory has ceased to apply, any more than your inability to calculate the aerodynamics of a 747 on an atom-by-atom basis implies that the 747 is not made out of atoms. Whatever approximation you use, it works to the extent that it approximates the ideal Bayesian calculation - and fails to the extent that it departs.

The practical upshot of seeing Bayesianism as an ideal to be approximated, I think, is this: you should avoid engaging in any reasoning that's demonstrably nonsensical in Bayesian terms. Furthermore, Bayesian reasoning can be fruitfully mined for heuristics that are useful in the real world. That's an idea that actually has real-world applications for human beings, hence the title of this post, "Bayesianism for Humans."

Here's my attempt to make an initial list of more directly applicable corollaries to Bayesianism. Many of these corollaries are non-obvious, yet eminently sensible once you think about them, which I think makes for a far better argument for Bayesianism than Dutch Book-type arguments with little real-world relevance. Most (but not all) of the links are to posts within the sequences, which hopefully will allow this post to double as a decent introductory guide to the parts of the sequences that explain Bayesianism.

Watch out for base rate neglect. It's why even experts screw up in one of the standard problems used to explain Bayes' Theorem. Even when you don't know what the base rate is, there are times when you ought to expect it to be low, particularly if you're trying to detect

...
Why didn't people (apparently?) understand the metaethics sequence?
by ChrisHallquist — 2013-10-29T23:04:25.408Z

There seems to be a widespread impression that the metaethics sequence was not very successful as an explanation of Eliezer Yudkowsky's views. It even says so on the wiki. And frankly, I'm puzzled by this... hence the "apparently" in this post's title. When I read the metaethics sequence, it seemed to make perfect sense to me. I can think of a couple things that may have made me different from the average OB/LW reader in this regard:

I read Three Worlds Collide before doing my systematic read-through of the sequences.

I have a background in academic philosophy, so I had a similar thought to Richard Chapell's linking of Eliezer's metaethics to rigid designators independently of Richard.

Reading the comments on the metaethics sequence, though, hasn't enlightened me about what exactly people had a problem with, aside from a lot of arguing about definitions over whether Eliezer counts as a relativist.

What's going on here? I ask mainly because I'm thinking of trying to write a post (or sequence?) explaining the metaethics sequence, and I'm wondering what points I should address, what issues I should look out for, etc.
Meetup : Meetup Bolder CO
by yakurbe0112 — 2013-10-28T15:42:08.514Z

Discussion article for the meetup : Meetup Bolder CO

WHEN:
30 October 2013 07:00:00PM (-0600)

WHERE:
Old Chicago 1102 Pearl St, Boulder, CO

Last time we decided that the topic for this meeting would be what we want from lesswrong and what we should do to make it happen.

Discussion article for the meetup : Meetup Bolder CO