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komponisto comments on What is Bayesianism? - Less Wrong

81 Post author: Kaj_Sotala 26 February 2010 07:43AM

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Comment author: woozle 28 February 2010 12:48:56AM -2 points [-]

Okay, I'm rising to the bait here...

I would really appreciate it if people would be more careful about passing on memes regarding subjects they have not researched properly. This should be a basic part of "rationalist etiquette", in the same way that "wash your hands before you handle food" is part of common eating etiquette.

I say this because I'm finding myself increasingly irritated by casual (and ill-informed) snipes at the 9/11 Truth movement, which mostly tries very hard to be rational and evidence-based:

Or take the debate we had on 9/11 conspiracy theories. Some people thought that unexplained and otherwise suspicious things in the official account had to mean that it was a government conspiracy. Others considered their prior for "the government is ready to conduct massively risky operations that kill thousands of its own citizens as a publicity stunt", judged that to be overwhelmingly unlikely, and thought it far more probable that something else caused the suspicious things.

This claim is both a straw-man and a false dilemma.

The straw-man: Most of the movement now centers around the call for a new investigation, not around claims that "Bush did it".

Some of us (I include myself as a "truther" only because I agree with their core conclusions; I am not a member of any 9/11-related organization) may believe it likely that the government did something horrendous, but we realize the evidence is weak and circumstantial, that it is unclear exactly what the level of involvement (if any) was, and that the important thing is for a proper inquiry to be conducted.

What is clear from the evidence available is that there has been a horrendous cover-up of some sort, and that the official conclusions do not make sense.

The false dilemma: Where "A" is {there is strong evidence that the official story is substantially wrong, and therefore a proper investigation should be conducted} and "B" is {the government was clearly directly responsible for initiating the whole thing}, believing A does not necessitate believing B. Refuting B (if argument by ridicule is considered an acceptable form of refutation, that is) does not refute A.

I'm still keen on discussing this rationally with anyone who thinks the Truth movement is irrational. RobinZ offered to discuss this further, but 7 months later he still hasn't had time to do more than allude to his general position without actually defining it.

Here are my positions on this issue. I would appreciate it if someone would kindly demolish them and show me what an utterly deluded fool I've been, so that I can go back to agreeing with the apparent rational consensus on this issue -- which seems to be, in essence, that there's nothing substantially wrong with the official story. (If anyone can point me to a concise presentment of what everyone here more or less believes happened on 9/11, I would very much like to see it.)

And if nobody can do that, then could we please stop the casual sniping? Whether or not you believe the official story, you at least have to agree that we really shouldn't be trying to silence skeptical inquiry on any issue, much less one of such importance.

Comment author: komponisto 28 February 2010 05:48:43AM *  8 points [-]

The problem you have is the one shared by everyone from devotees of parapsychology to people who believe Meredith Kercher was killed in an orgy initiated by Amanda Knox: your prior on your theory is simply way too high.

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, that the puzzling details you cite, even in their totality, fail to make a dent in a rational observer's credence of (more or less) the official story.

You might try asking yourself: if the official story were in fact correct, wouldn't you nevertheless expect that there would be strange facts that appear difficult to explain, and that these facts would be seized upon by conspiracy theorists, who, for some reason or another, were eager to believe the government may have been involved? And that they would be able to come up with arguments that sound convincing?

I want to stress that it is not the fact that the terrorists-only theory is officially sanctioned that makes it the (overwhelming) default explanation; as the Kercher case illustrates, sometimes the official story is an implausible conspiracy theory! Rather, it is our background knowledge of how reality operates -- which must be informed, among other things, by an acquaintance with human cognitive biases.

"Not silencing skeptical inquiry" is a great-sounding applause light, but we have to choose our battles, for reasons more mathematical than social: there are simply too many conceivable explanations for any given phenomenon, for it it be worthwhile to consider more than a very small proportion of them. Our choice of which to consider in the first place is thus going to be mainly determined by our prior probabilities -- in other words, our model of the world. Under the models of most folks here, 9/11 conspiracy theories simply aren't going to get any time of day.

If it's different for you, 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. (If there aren't any, then I think you severely overestimate the tendency of people's beliefs to be entangled with reality.)

Comment author: Morendil 28 February 2010 10:32:50AM *  12 points [-]

"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.

Comment author: ciphergoth 28 February 2010 10:48:45AM 5 points [-]

the intellectual analogue of terrorism.

I like this comment lots, but I think this comparison is inadvisable hyperbole.

Comment author: Morendil 28 February 2010 11:42:55AM 4 points [-]

Perhaps "asymmetric warfare" would be a better term than "terrorism". More general, and without the connotations which I agree make that last line something of an exaggeration.

Comment author: woozle 28 February 2010 04:14:53PM 0 points [-]

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"?

Comment author: komponisto 28 February 2010 06:49:48PM 5 points [-]

I do not claim that the government was responsible for 9/11; I believe the evidence, if properly examined, would probably show this

This is a flat-out Bayesian contradiction.

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

It's not an easy problem, in general -- hence LW!

But we can always start by doing the Bayesian calculation. What's your prior for the hypothesis that the U.S, government was complicit in the 9/11 attacks? What's your estimate of the strength of each of those pieces of evidence you think is indicative of a conspiracy?

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.

You misunderstood. I was talking about your failure to dismiss 9/11 conspiracy theories. I was asking whether there were any conspiracy theories that you would be willing to dismiss without research.

Comment author: woozle 28 February 2010 11:07:54PM *  -1 points [-]

Again, I think this question is a diversion from what I have been arguing; its truth or falseness does not substantially affect the truth or falseness of my actual claims (as opposed to beliefs mentioned in passing).

That said, I made a start at a Bayesian analysis, but ran out of mental swap-space. If someone wants to suggest what I need to do next, I might be able to do it.

Also vaguely relevant -- this matrix is set up much more like a classical Bayesian word-problem: it lists the various pieces of evidence which we would expect to observe for each known manner in which a high-rise steel-frame building might run down the curtain and join the choir invisible, and then shows what was actually observed in the cases of WTC1, 2, and 7.

Is there enough information there to calculate some odds, or are there still bits missing?

You misunderstood. I was talking about your failure to dismiss 9/11 conspiracy theories. I was asking whether there were any conspiracy theories that you would be willing to dismiss without research.

No, not really. I think of that as my "job" at Issuepedia: don't dismiss anything without looking at it. Document the process of examination so that others don't have to repeat it, and so that those who aren't sure what to believe can quickly see the evidence for themselves (rather than having to go collect it) -- and can enter in any new arguments or questions they might have.

Does that process seem inherently flawed somehow? I'm not sure what you're suggesting by your use of the word "failure" here.

Comment author: komponisto 01 March 2010 02:06:30AM *  6 points [-]

(Some folks have expressed disapproval of this conversation continuing in this thread; ironically, though, it's becoming more and more an explicit lesson in Bayesianism -- as this comment in particular will demonstrate. Nevertheless, after this comment, I am willing to move it elsewhere, if people insist.)

Again, I think this question is a diversion from what I have been arguing; its truth or falseness does not substantially affect the truth or falseness of my actual claims (as opposed to beliefs mentioned in passing)

You're in Bayes-land here, not a debating society. Beliefs are what we're interested in. There's no distinction between an argument that a certain point of view should be taken seriously and an argument that the point of view in question has a significant probability of being true. If you want to make a case for the former, you'll necessarily have to make a case for the latter.

That said, I made a start at a Bayesian analysis, but ran out of mental swap-space. If someone wants to suggest what I need to do next, I might be able to do it.

Here's how you do a Bayesian analysis: you start with a prior probability P(H). Then you consider how much more likely the evidence is to occur if your hypothesis is true (P(E|H)) than it is in general (P(E)) -- that is, you calculate P(E|H)/P(E). Multiplying this "strength of evidence" ratio P(E|H)/P(E) by the prior probability P(H) gives you your posterior (updated) probability P(H|E).

Alternatively, you could think in terms of odds: starting with the prior odds P(H)/P(~H), and considering how much more likely the evidence is to occur if your hypothesis is true (P(E|H)) than if it is false (P(E|~H)); the ratio P(E|H)/P(E|~H) is called the "likelihood ratio" of the evidence. Multiplying the prior odds by the likelihood ratio gives you the posterior odds P(H|E)/P(~H|E).

One of the two questions you need to answer is: by what factor do you think the evidence raises the probability/odds of your hypothesis being true? Are we talking twice as likely? Ten times? A hundred times?

If you know that, plus your current estimate of how likely your hypothesis is, division will tell you what your prior was -- which is the other question you need to answer.

Is there enough information there to calculate some odds, or are there still bits missing?

If there's enough information for you to have a belief, then there's enough information to calculate the odds. Because, if you're a Bayesian, that's what these numbers represent in the first place: your degree of belief.

I'm not sure what you're suggesting by your use of the word "failure" here

"Your failure to dismiss..." is simply an English-language locution that means "The fact that you did not dismiss..."

Comment author: Morendil 28 February 2010 04:27:53PM 2 points [-]

This thread doesn't belong under the "What is Bayesianism" post. I advise taking it to the older post that discussed "Truthers".