What is Bayesianism?

Here is a more general definition of "pure frequentism" (which includes frequentists such as Reichenbach):

Consider an assertion of probability of the form "This X has probability p of being a Y." A frequentist holds that this assertion is meaningful only if the following conditions are met:

1. The speaker has already specified a determinate set X of things that actually have or will exist, and this set contains "this X".

2. The speaker has already specified a determinate set Y containing all things that have been or will be Ys.

The assertion is true if the proportion of elements of X that are also in Y is precisely p.

A few remarks:

1. The assertion would mean something different if the speaker had specified different sets X and Y, even though X and Y aren't mentioned explicitly in the assertion.

2. If no such sets had been specified in the preceding discourse, the assertion by itself would be meaningless.

3. However, the speaker has complete freedom in what to take as the set X containing "this X", so long as X contains X. In particular, the other elements don't have to be exactly like X, or be generated by exactly the same repeatable procedure, or anything like that. There are practical constraints on X, though. For example, X should be an interesting set.

4. [ETA:] An important distinction between Bayesianism and Frequentism is this: Note that, according to the above, the correct probability has nothing to do with the state of knowledge of the speaker. Once the sets X and Y are determined, there is an objective fact of the matter regarding the proportion of things in X that are also in Y. The speaker is objectively right or wrong in asserting that this proportion is p, and that rightness or wrongness had nothing to do with what the speaker knew. It had only to do with the objective frequency of elements of Y among the elements of X.

I'm sorry to see such wrongheaded views of frequentism here. Frequentists also assign probabilities to events where the probabilistic introduction is entirely based on limited information rather than a literal randomly generated phenomenon. If Fisher or Neyman was ever actually read by people purporting to understand frequentist/Bayesian issues, they'd have a radically different idea. Readers to this blog should take it upon themselves to check out some of the vast oversimplifications... And I'm sorry but Reichenbach's frequentism has very little to do with frequentist statistics--. Reichenbach, a philosopher, had an idea that propositions had frequentist probabilities. So scientific hypotheses--which would not be assigned probabilities by frequentist statisticians--could have frequentist probabilities for Reichenbach, even though he didn't think we knew enough yet to judge them. He thought at some point we'd be able to judge of a hypothesis of a type how frequently hypothesis like it would be true. I think it's a problematic idea, but my point was just to illustrate that some large items are being misrepresented here, and people sold a wrongheaded view. Just in case anyone cares. Sorry to interrupt the conversation (errorstatistics.com)

What does that mean for frequentist statistical inference? Well, it's forbidden to assign probabilities to anything that is deterministic in your model of reality.

Wait - Bayesians can assign probabilities to things that are deterministic? What does that mean?

What would a Bayesian do instead of a T-test?

the tendency to think of probabilities as inherent properties of objects.

yeah, this was my intuitive reason for thinking frequentists are a little crazy.

thanks, that's what I was looking for. would it be correct to say that in the frequentist interpretation your confidence interval narrows as your trials approach infinity?

Heh, that's a cheeky example. To explain why it's cheeky, I have to briefly run through it, which I'll do here (using Jaynes's symbols so whoever clicked through and has pages 22-24 open can directly compare my summary with Jaynes's exposition).

Call N the sample size and θ the minimum possible widget lifetime (what bill calls X). Jaynes first builds a frequentist confidence interval around θ by defining the unbiased estimator θ∗, which is the observations' mean minus one. (Subtracting one accounts for the sample mean being >θ.) θ∗'s probability distribution turns out to be y^(N-1) exp(-Ny), where y = θ∗ - θ + 1. Note that y is essentially a measure of how far our estimator θ∗ is from the true θ, so Jaynes now has a pdf for that. Jaynes integrates that pdf to get y's cdf, which he calls F(y). He then makes the 90% CI by computing [y1, y2] such that F(y2) - F(y1) = 0.9. That gives [0.1736, 1.8259]. Substituting in N and θ∗ for the sample and a little algebra (to get a CI corresponding to θ∗ rather than y) gives his θ CI of [12.1471, 13.8264].

For the Bayesian CI, Jaynes takes a constant prior, then jumps straight to the posterior being N exp(N(θ - x1)), where x1's the smallest lifetime in the sample (12 in this case). He then comes up with the smallest interval that encompasses 90% of the posterior probability, and it turns out to be [11.23, 12].

Jaynes rightly observes that the Bayesian CI accords with common sense, and the frequentist CI does not. This comparison is what feels cheeky to me.

Why? Because Jaynes has used different estimators for the two methods [edit: I had previously written here that Jaynes implicitly used different estimators, but this is actually false; when he discusses the example subsequently (see p. 25 of the PDF) he fleshes out this point in terms of sufficient v. non-sufficient statistics.]. For the Bayesian CI, Jaynes effectively uses the minimum lifetime as his estimator for θ (by defining the likelihood to be solely a function of the smallest observation, instead of all of them), but for the frequentist CI, he explicitly uses the mean lifetime minus 1. If Jaynes-as-frequentist had happened to use the maximum likelihood estimator -- which turns out to be the minimum lifetime here -- instead of an arbitrary unbiased estimator he would've gotten precisely the same result as Jaynes-as-Bayesian.

So it seems to me that the exercise just demonstrates that Bayesianism-done-slyly outperformed frequentism-done-mindlessly. I can imagine that if I had tried to do the same exercise from scratch, I would have ended up faux-proving the reverse: that the Bayesian CI was dumber than the frequentist's. I would've just picked up a boring, old-fashioned, not especially Bayesian reference book to look up the MLE, and used its sampling distribution to get my frequentist CI: that would've given me the common sense CI [11.23, 12]. Then I'd construct the Bayesian CI by mechanically defining the likelihood as the product of the individual observations' likelihoods. That last step, I am pretty sure but cannot immediately prove, would give me a crappy Bayesian CI like [12.1471, 13.8264], if not that very interval.

Ultimately, at least in this case, I reckon your choice of estimator is far more important than whether you have a portrait of Bayes or Neyman on your wall.

[Edited to replace my asterisks with ∗ so I don't mess up the formatting.]

excellent paper, thanks for the link.

My intuition would be that the interval should be bounded above by 12 - epsilon, since the probability that we got one component that failed at the theoretically fastest rate seems unlikely (probability zero?).

Yes, that would be better.

I'm on it.

Continuing.

If you thought a cold was more likely, well, that was the answer I was after.

Part of the great danger in explaining a High topic is that people who haven't been able to understand High topics are super wary about looking like an idiot. Math is the most obvious High topic that people hate trying to understand. They would much rather admit to fearing math than trying and failing at understanding it.

This is sad, to me, because math isn't really that hard to understand. It is a daunting subject that never ends but the fundamentals are already understood by anyone who functions in society. They just never put all the pieces together with the right terms.

I am firmly convinced that the Way of Bayes is like this. The sequences are, for the most part, about subjects that could be easy to understand. They make intuitive sense. The details and the numbers are a pain, but the concept itself is something I could explain to nearly everyone I know. (So I think. I haven't actually tried yet.)

A sentence like the one I quoted above is one that will put a layperson on defensive. This pushes Bayesianism into the realm of High topics: Topics that are grasped by the Smart people; the intellectual elite. Asking them questions at all makes them realize they don't know the answer. This is scary. Immediately answering the question and telling them the answer should be obvious could easily make them feel awkward, even if they got the answer correct.

Articles explaining "obvious" things are often explaining not-obvious things and assume that you are following them each step of the way. These articles are full of trick questions and try to make you second guess yourself in an effort to show you what you do not know. This is scary and elitist to someone who has sold their own intelligence short.

Your example is so minor that most people wouldn't have a problem with it. I bring it up because I am picky. This is an example of aiming far, far too high. The audience at LessWrong reads a question/answer like this and enjoys it. They like learning they are wrong and revel in the introspection that follows as they chase down the error in the machine so they can fix it. A layperson dreads this. They think it means they are stupid and unable to understand. They fail at the competition of intelligence whether the competition actually exists or not.

Even if a brain tumor caused a headache every time, and a cold caused a headache only one per cent of the time (say), having a cold is so much more common that it's going to cause a lot more headaches than brain tumors do.

I think this belongs in the description of the example. You could even leave out the actual numbers because they only matter for the people that have the exact numbers. It takes too long to explain that you just made the numbers up because:

• Every word is more processing that needs to be done
• The intended audience are probably inexperienced at skimming these sorts of topics
• The numbers really are irrelevant
• Someone will disagree with the numbers and make a big stink about something that was irrelevant

Bayes' theorem, basically, says that if cause A might be the reason for symptom X, then we have to take into account both the probability that A caused X (found, roughly, by multiplying the frequency of A with the chance that A causes X) and the probability that anything else caused X. (For a thorough mathematical treatment of Bayes' theorem, see Eliezer's Intuitive Explanation.)

And... the layperson just zoned out. This is the big obstacle in trying to describe Bayesianism. Math scares people away. Even people who are good at math will glaze over when they see As and Xs and words like "probability." I have no idea how to get around this obstacle, honestly. Your attempt was solid. But I still think this is the paragraph where you will lose the lowest rung of your audience.

There should be nothing surprising about that, of course.

What if they were surprised? What if their whole world reeled at the question of what causes headaches? What if, horrifically, they completely misunderstood the previous example and are currently pondering if their headache means they have a brain tumor?

If they are completely bewildered right now, telling them they shouldn't be surprised will make them feel dumb. Even if they are dumb, your article shouldn't make them feel dumb. It should make them feel smart.

Suppose you're outside, and you see a person running. They might be running for the sake of exercise, or they might be running because they're in a hurry somewhere, or they might even be running because it's cold and they want to stay warm. To figure out which one is the case, you'll try to consider which of the explanations is true most often, and fits the circumstances best.

I don't think this example clarifies much. A bullet list:

• "they're in a hurry somewhere" sounds funny to me. Perhaps, "they're in a hurry to get somewhere" or "they're in a hurry" works better? This could be a style thing.
• Running because it's cold will mean random things to random people. If I am outside and its cold I don't think of running. I think of doing hard work like shoveling snow or simply going inside. The reason I bring this up is because every second someone thinks, "That's weird, why would you run outside if it's cold?" is a second that the points you made above get shoved further away from the points below.
• To figure out which one is the case, people could think of (a) asking the runner (b) looking for more evidence. Judging which reason happens most often may not translate well. I didn't even attach this language to the headache on first read. If you know the answer you can see the relation but I am not confident that it is available for every reader.

More coming if you still want it. My lunch break is over. :)

Interesting that you find the usage of "you" and "we" patronizing. I hadn't thought of it like that - I intended it as a way to make the post less formal and build a more comfortable atmosphere to the reader.

Using "you" is a two-edged sword; it can create greater intimacy with your audience, but only if you know your audience well enough, and don't mind polarizing your response, or are willing to limit yourself to hypotheticals (e.g. "if you walked into a doctor's office")

If you're less certain of your audience, but still want the strong intimacy or identification response, you may want to use "I" instead. By telling a story that your reader can relate to... that is, a story of how you made this discovery, found out why it's important, or applied it in some way to achieve a goal the reader shares or recognizes as valuable, then you allow the reader to simply identify with you on a less conscious/contentious level.

(Notice, for example, how many of Eliezer's best posts begin with such a story, either about Eliezer or some fictional characters.)

Hmm, what do people think - if we end up rewriting this, should I just edit this post? Or make an entirely new one? Perhaps keep this one as it is, but work the changes into a future one that's longer?

Personally, I think if it's just minor stylistic changes in expressing the same material, editing the post is the way to go; if it's adding more material, or expressing it radically differently, then a new post is appropriate.

it's fine the way it is I think, it covers enough without being too specific. great post.

jimrandomh claimed that frequentists don't report amounts of evidence. So you object that measuring in decibels is not how they don't report it? If they don't reports amount of evidence, then of course they don't report it in the precise way in the example.

Just remember that Jaynes was not a mathematician and many of his claims about pure mathematics (as opposed to computations and their applications) in the book are wrong. Especially, infinity is not mysterious.

I agree. The line between belief and decision is the line between 3 and 4 in that list and it is such a clean line that the von Neumann-Morgenstern axioms can be (and usually are) presented about a frequentist world.

Jonathan's post doesn't seem like much of an argument but more of criticism. There's lots more to write on this topic.

By any standard you had a successful Hacker News post -- it was on the front page for most of the morning, which is good. The number of votes is not meaningful at all on Hacker News so there's no conversion rate. Also, I strongly suspect that many of the initial early votes on HN came from primary LW users following my link and then upvoting, possibly even people that didn't upvote it on LW.

In these cases, the 'conspiracy theorists' and peace activists were right; and I can't think of any where they were wrong. So they have more credibility than the official report."

Knowing that the official report contains information that's false, doesn't lead you to know what's true.

You know, I have little interest in 9/11 Truth, but I have no patience for the "but it would be so obvious" reply to Truthers. Here is how that conversation translates in my head:

Truther: I think the towers came down due to a deliberate demolition by our government. I think this because thus and so.

Non-Truther: But the government would never have done anything so easy to find out about, because it would carry massive risk. Everybody would know about it.

Truther: Well, if people were paying attention to thus and so, they'd know -

Non-Truther: BUT SINCE I DIDN'T ALREADY KNOW ABOUT THUS AND SO IT'S CLEARLY NOT SOMETHING EVERYBODY KNOWS ABOUT AND I CAN'T HEAR YOU NANANANANANANANA.

We're talking about people already at the top of the social hierarchy risky death and eternal shame for them and their families in hopes the hundreds of people part of the conspiracy keep quiet and that no damning evidence of a remarkable complicated plot is left behind.

Well, there is a lot of evidence left behind and that has been cited over and over.

The government's willingness to kill it's own citizens, such as it is, less often carries over to civilians and even less often carries over to rich white people on Wall Street.

AFAIK none of the people killed was exceptionally rich and/or powerful.

And for something that has help shaped the country... well remarkably little has changed in the direction that administration wanted to things to go.

Wait, what???

If they're so powerful why not get someone else elected President?

Someone else? What are you talking about, every President in the last decades has been a member of one of the same two parties. Obama has not significantly changed the foreign policy and is moving in the same direction.

Forged documents and lies are not enough to convince the public opinion or better to arouse strong emotions, something more salient is needed. You have to remember, at 9-11 basically the whole world stood still watching the events unfold. Wikipedia:

The NATO council declared that the attacks on the United States were considered an attack on all NATO nations and, as such, satisfied Article 5 of the NATO charter

http://en.wikipedia.org/wiki/September_11_attacks#cite_note-155

Btw article 5 allows the use of armed(military) force. This was the official NATO position even before there was any investigation as to who was supposedly behind the "attacks".

Anyone arguing against military action can be and still is decried as unpatriotic, callous towards the families of those who died. You cannot achieve this with just a batch of documents.

Following your analogy, what is the equivalent to Shia Islam?

Put another way: Bayesianism as opposed to what?

I PM'ed you regarding this thread. (I mention it here because I seem to recall that you're subject to a bug that prevents you from getting message/reply notifications.)

Agreed, I did not find the "Intuitive Explanation" to be particularly intuitive even after multiple readings. Understanding the math and principles is one thing, but this post actually made me sit up and go, "Oh, now I see what all the fuss is about," outside a relatively narrow range of issues like diagnosing cancer or identifying spam emails.

Now I get it well enough to summarize: "Even if A will always cause B, that doesn't mean A did cause B. If B would happen anyway, this tells you nothing about whether A caused B."

Which is both a "well duh" and an important idea at the same time, when you consider that our brains appear to be built to latch onto the first "A" that would cause B, and then stubbornly hang onto it until it can be conclusively disproven.

That's a "click" right there, that makes retroactively comprehensible many reams of Eliezer's math rants and Beisutsukai stories. (Well, not that I didn't comprehend them as such... more that I wasn't able to intuitively recreate all the implications that I now think he was expecting his readers to take away.)

So, yeah... this is way too important of an idea to have math associated with it in any way. ;-)

Personally it bothers me that the explanation asks a question which is numerically unanswerable, and then asserts that rationalists would answer it in a given way. Simple explanations are good, but not when they contain statements which are factually incorrect.

But, looking at the karma scores it appears that you are correct that this is better for many people. ^_^;

Hmmmm.... that's an interesting article too, but it focuses on a different question, the question what knowledge really means, and uses AI concepts to discuss that (somewhat related to Searle's Chinese Room gedankenexperiment.)

However, I think the article discussed here is a bit more directly connected to Bayesianism. It's clear what Bayes Theorem means, but what many people today mean with Bayesianism, is somewhat of a loose extrapolation of that -- or even just a metaphor.

I think the article does a good job at explaining the current use.

Ah, but... what are the odds that A HIJACKER WOULD FLY IN BUSINESS CLASS??!?

For example, your first "unanswered" question just sounds crazy! I mean, HOLY SHIT! the hijackers names aren't on the manifest! That is huge! And yet, of course they absolutely are on the flight manifests and, indeed, they flew under their own names. Indeed, we even have seating charts. For example, Mohamed Atta was in seat 8D. That's business class, btw.

This is a crowning moment of awesome.

One can't both think something is likely and think the evidence is weak and circumstantial!

One definitely can. What else is one supposed to do when evidence is weak and circumstantial? Assign probabilities that sum to less than one?

But if you do you're obligated to defend your belief.

You're really not. You are not epistemicaly obliged to accept the challenge of another individual and subject your reasoning to their judgement in the form they desire. That is sometimes a useful thing to do and sometimes it is necessary for the purpose of persuasion. Of course, it's usually more practical to attack their beliefs instead. That tends to give far more status.

Part of the point is you're not allowed to do this!

1. I'm allowed to believe whatever I want; I'm just not allowed to try to convince you of it unless I have a rational argument.

2. Isn't this what Bayesianism is all about -- reaching the most likely conclusion in the face of weak or inconclusive evidence? Or am I misunderstanding something?

3. I do have arguments for my belief, but I'm not really prepared to spend the time getting into it; it's not essential to my main thesis, and I mentioned it only in passing as a way of giving context, to wit: "some people believe this, and I'm not trying to dismiss them, partly because I happen to agree with them, but that belief is entirely beside the point".

On your OT: You win a cookie! I had to research this a bit to figure out what happened, but apparently some 9/11 researchers found a list of passenger-victims and thought it was a passenger manifest. One anomaly does remain in that 6 of the alleged hijackers have turned up alive, but I wouldn't call that enough of an anomaly to be worth worrying about.

(Found the offending factoid under "comments" on the position page; fixing it...)

That is a valuable point, and I have amended my A8 response to "MAYBE". The one detail I'm still not sure of is whether pilots would have relinquished control under those circumstances. Can anyone point to the actual text of the "Common Strategy"?

"Pilots for 911 Truth" has this to say:

I find it hard to believe Capt. Burlingame gave up his ship to Hani Hanjour pointing a boxcutter at him. Pilots know The Common Strategy prior to 9/11. Capt. Burlingame would have taken them where they wanted to go, but only after seeing more than a "boxcutter" or knife. ... The pilots' number 1 priority is the safety of the passengers. Number 2 priority is to get them to their destination on time. Pilots dont just give up their airplane to someone with a knife.. regardless of what the press has told you about The Common Strategy prior to 9/11.

"Screw Loose Change" seems to find this statement incredibly offensive, but offers only an emotional argument in response (argument from outrage?) and ignores the original point that these pilots were experienced in this sort of combat and certainly could have fought off attackers with boxcutters, with the "Common Strategy" being the only possible constraint on doing so.

I've added your proposed questions to the questionnaire, somewhat modified.

My answers are:

• NO: not more likely, just possible -- what actually happened must be determined by the evidence. David Brin, for example, argues that said incompetence was a by-product of a "war on professionalism" waged by the Bush administration. (I would also argue that the question as phrased implies that it is reasonable to judge the question of {whether malice was involved} entirely on the basis of {how "likely" it seems}, and that this is therefore privileging the hypothesis that malice was not involved.)
• "starving the beast", albeit in a somewhat broader sense than described by Wikipedia: shrink the government by rendering it incompetent, thus eroding support (and hence funding) for government activities
• I'm not sure what you're getting at here; my immediate answer is "THAT DEPENDS" -- given the range of possible scenarios in which the government is complicit, the incompetence:malice ratio has a wide range of possible values. I don't know if I'm answering the question in the spirit in which it was asked, however.

I've rephrased that last question as a matter of consistency: "Do you believe that the levels of government malice OR stupidity/incompetence displayed regarding Katrina are consistent with whatever levels of government malice or incompetence/stupidity you believe were at work on 9/11?" to which I answer (a) it's within the range of possibilities, given that the evidence remains unclear as to exactly what the Administration's involvement was on 9/11, (b) the issue of consistency between Katrina and 9/11 argues against the idea that Bushco were "just doing the best they could" on 9/11, since they clearly didn't do this for Katrina; (c) if the evidence pointed to a significantly different level of competence on 9/11 than it does for Katrina, would this be grounds for rejecting the evidence, grounds for trying to determine what might have changed, or grounds for suspecting that someone's "anomaly detectors are tuned too high"?

Please note, however, that I consider all of these issues to be very much diversions from the main question of whether a proper investigation is needed.

I vote for malice with regard to Katrina. It's not that there were political gains to be had from that particular disaster happening but the then-government decided to let it happen anyway out of malice. It's that their generally malicious political ideology was on balance a very successful one, but had as one of its weaknesses that it sometimes led to this kind of politically-harmful disaster.

"Not silencing skeptical inquiry" is a great-sounding applause light

The main issue with it has been noted multiple times by people like Dawkins: there is an effort asymmetry between plucking a false but slightly believable theory out of thin air, and actually refuting that same theory. Making shit up takes very little effort, while rationally refuting random made-up shit takes the same effort as rationally refuting theories whose refutation yields actual intellectual value. Creationists can open a hundred false arguments at very little intellectual cost, and if they are dismissed out of hand by the scientific establishment they get to cry "suppression of skeptical inquiry".

This feels related to pjeby's recent comments about curiosity. The mere feeling that "there's something odd going on here", followed by the insistence that other people should inquire into the odd phenomenon, isn't valid curiosity. That's only ersatz curiosity. Real curiosity is what ends up with you actually constructing a refutable hypothesis, and subjecting it to at least the kind of test that a random person from the Internet would perform - before actually publishing your hypothesis, and insisting that others should consider it carefully.

Inflicting random damage on other people's belief networks isn't promoting "skeptical inquiry", it's the intellectual analogue of terrorism.

Again, you're addressing a straw man -- not my actual arguments. I do not claim that the government was responsible for 9/11; I believe the evidence, if properly examined, would probably show this -- but my interest is in showing that the existing explanations are not just inadequate but clearly wrong.

So, okay, how would you tell the difference between an argument that "sounds convincing" and one which should actually be considered rationally persuasive?

My use of the "applause light" was an attempt to use emotion to get through emotional barriers preventing rational examination. Was it inappropriate?

"There are simply too many conceivable explanations for any given phenomenon for it to be worthwhile to consider more than a very small proportion of them."

I agree. Many of the conclusions reached by the 9/11 Commission are, however, not among that small proportion. Many questions to which we need answers were not even addressed by the Commission. (Your statement here strikes me as a "curiosity stopper".)

Under the models of most folks here, 9/11 conspiracy theories simply aren't going to get any time of day.

This is the problem, yes. What's your point?

I'd be curious to know what kind of ideas with substantial numbers of adherents you would feel safe in dismissing without bothering to research.

None that I can think of. Again, what's your point? I am not "dismissing" the dominant conclusion, I am questioning it. I have, in fact, done substantial amounts of research (probably more than anyone reading this). If anyone is actually dismissing an idea with substantial numbers of adherents, it is those who dismiss "truthers" without actually listening to their arguments.

Are you arguing that "people are irrational, so you might as well give up"?

Simply put, the events of 9/11 are so overwhelmingly more likely a priori to have been the exclusive work of a few terrorists than the product of a conspiracy involving the U.S. government

Based on what facts do you think so?

it is our background knowledge of how reality operates -- which must be informed, among other things, by an acquaintance with human cognitive biases.

Where did you get your background knowledge in regards to terrorism and geopolitics from?

The way you argue is the way the average person thinks, because the average has never been able to look behind the scenes of what happens in politics and instead gets his news from the media.

I used the term "truther" as an attempt to be honest -- admitting that I pretty much agree with them, rather than trying to pretend to be a devil's advocate or fence-sitter.

I don't see how that's a failure of filtering.

The rest of your first paragraph is basically ad-hominem, as far as serious discussion of this issue goes. If I'm upset, I try not to let it dominate the conversation -- this is a rationalist community, after all, and I am a card-carrying rationalist -- but I also believe it to be justified, for reasons I explained earlier.

"That's normal" -- so are you in the "people aren't rational so you might as well give up" camp along with komponisto? What's your point?

If you want to calibrate, you could look at Holocaust and HIV denial. I'm told they are well described by the above quote. or any medical controversy.

Holocaust denial and HIV denial are easily refuted by the available evidence -- along with global warming denial, evolution denial, moon landing denial, and most religions. 9/11 anomalies manifestly are not, given that I've been trying for years to elicit rational rebuttals and have come up with precious little. Please feel free to send me more.

Often it is best to silence incompetent skeptical inquiry.

Do you really believe this? Why? Who determines that it is incompetent?

Kaj, I've always enjoyed your posts, so I felt bad picking on you and I apologize if I jumped down your throat. It seemed time to say something about this because I've been seeing it over and over again in lots of otherwise very rational/reality-based contexts, and your post finally pushed that button.

For reformulating your summary, I'd have to go read the original discussion, but you didn't link to it.

It's not that it needs to reflect my views, it's that I think we need a more... rigorous? systematic?... way of looking at controversies.

Yes, many of them can be dismissed without further discussion -- global warming denial, evolution denial, holocaust denial, et freaking cetera -- but there are specific reasons we can dismiss them, and I don't think those reasons apply to 9/11 (not even to the official story -- parts of it seem very likely to be true).

Proposed Criteria for Dismissing a Body of Belief

Terminology:

• a "claim" is an argument favoring or supporting the body of belief
• a "refutation" is a responding argument which shows the claim to be invalid (in a nested structure -- responses to refutations are also "claims", responses to those claims are also "refutations", etc)

Essential criteria:

• the work has been done of examining the claims and refuting them
• no claims remain unrefuted

A further cue, sufficient but not necessary:

• those promoting the ideology never bring up the refutations of their claims unless forced to do so, even though there is reason to believe they are well aware of those refutations

Any objection to those ground rules? The first set is required so that the uninformed (e.g. those new to the discussion) will have a reference by which to understand why the seemingly-persuasive arguments presented in favor of the given belief system are, in fact, wrong; the final point is a sort of short-cut so we don't waste time dealing with people who are clearly being dishonest.

I submit that, by these rules, we can safely dismiss (at a minimum) global warming denial, evolution denial, Young Earth theories, Biblical literalism, holocaust denial, HIV denial, and anti-gay rhetoric... but not the 9/11 "truth movement".

Kaj,

I think it was not wise and maybe even a bit provocative to use an example where you know that differing views exist in this forum and that is a source of heated debates. If you are really concerned about it as opposed to just signaling concern may I suggest to change it yourself in accordance with the point you are trying to make? Don't put the burden on others.

EDIT: impolite -> provocative

What were your thoughts on Eliezer's Meta-Truther Conspiracy post?

He brings up a lot of hypotheses; let me see if I can (paraphrase and) respond to the major ones.

• "9/11 conspiracy theorists" are actually acting on behalf of genuine government conspirators. Their job is to plant truly unbelievable theories about what happened so that people will line up behind the official story and dismiss any dissenters as "just loony conspiracy theorists".

Well, yes, there's evidence that this is what has happened; it is discussed extensively here.

• The idea that the towers were felled by controlled demolition is loony.

No, it isn't. There is now a great deal of hard evidence pointing in this direction. It may turn out to be wrong, but it is absolutely not loony. See this for some lines of reasoning.

• "This attack would've had the same political effect whether the buildings came down entirely or just the top floors burned."

If anyone really believes that, I'll be happy to explain why I don't.

• The actual government involvement was to stand aside and allow the attack, which was in fact perpetrated by middle eastern agents, to succeed.

This is the lesser of the two major "conspiracy" theories, known as "let it happen on purpose" (LIHOP) and "make it happen on purpose" (MIHOP). MIHOP is generally presumed to be a core belief of all "truthers", though this is not in fact the case; there does not appear to be any clear consensus about which scenario is more likely, and (as I said earlier) the actual core belief which defines the "truther" movement is that the official story is significantly wrong and a proper investigation is needed in order to determine what really happened.

Imagine, for example, what the Challenger investigation would have found if Richard Feynman hadn't been there.

• Conspiracy theorists are all (or mostly) anti-government types.

Well, I can't speak for the rest of them, but I'm not. I strongly dislike how the government operates, but I see it as an essential invention -- something to repair, not discard. The "truther" movement doesn't seem to have any strong political leanings, either, though I might have missed something.

• Conspiracy theorists will find suspicious evidence, regardless of whether anything suspicious happened.

Ad-hominem. Is the evidence reasonable, or isn't it? If not, why not?

If there were a conspiracy, government inaction given foreknowledge of the attacks seems orders of magnitude more likely than any sort of controlled demolition, even for WTC7.

How likely does it seem that groups of foreign hijackers would succeed in taking control of 4 different planes using only box-cutters and piloting 3 of them into targets in two of the most heavily-guarded airspaces in the world, without even an attempt at interception? How likely is that no heads would roll as a consequence of this security failure? How likely is it that the plane flown into the Pentagon would execute a difficult hairpin turn in order to fly into the most heavily-protected side of the building? How likely is it that no less than three steel-framed buildings would completely collapse from fire and mechanical damage, for the first time in history, all on the same day? How likely is it that they would not just fall to the ground towards the side most heavily damaged but instead seemingly explode straight downward and outward into microscopic dust particles, leaving almost nothing (aside from the steel girders) larger than a finger, long after the impacts and when the fires were clearly dying down? How likely is it that anyone would try to claim that this was totally what you would expect to happen, even though the buildings were designed to handle such an impact? How likely is it that this would result in pools of molten steel, when jet fuel doesn't burn hot enough to melt steel?

Shall I go on?

If there were a conspiracy, government inaction given foreknowledge of the attacks seems orders of magnitude more likely than any sort of controlled demolition, even for WTC7.

Can you provide us with numbers please? In regards to WTC7 I bring up the following: What is the number of steel-frame buildings that collapsed due to damage by fire and some structural damage? AFAIK it is close to zero. And there are none that collapsed in essentially free-fall speed prior to WTC7(and the twin towers). So applying bayesian reasoning the probability of a demolition is certainly much higher.

You certainly can't talk about "orders of magnitude more likely" without providing any numbers.