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2irons comments on Don't You Care If It Works? - Part 1 - Less Wrong

4 Post author: Jacobian 29 July 2015 02:32PM

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Comment author: 2irons 29 July 2015 03:41:35PM *  6 points [-]

"Does this change your confidence in Bob managing your retirement investments?" - if he never held himself out as a quant based investor or using a method reliant on much analytical or quantitative research I wouldn't worry about it.

Maybe he's been good at choosing ETF's because he's great at listening to investors and trader chat - can feel which arguments are about to dominate the market and allocates capital accordingly. Maybe he sits by a high performing proprietory trading team in his bank and you're piggy backing off of all their trades at a fraction of the fee. As a fund manager I know several other managers who would have no hope of following most of the articles on this website, misunderstand probability at basic levels (this has been teased out by in depth conversations on things like card counting - where they are high conviction yet wrong) but yet who I'd still have to concede are likely to continue outperforming me in the market because they are great at the parts that count.

I think this is put best by Nassim Taleb in Anti-Fragile:

“In one of the rare noncharlatanic books in finance, descriptively called What I Learned Losing A Million Dollars, the protagonist makes a big discovery. He remarks that a fellow called Joe Siegel, the most active trader in a commodity called “green lumber” actually thought that it was lumber painted green (rather than freshly cut lumber, called green because it had not been dried). And he made a living, even a fortune trading the stuff! Meanwhile the narrator was into theories of what caused the price of commodities to move and went bust.

The fact is that predicting the orderflow in lumber and the price dynamics narrative had little to do with these details —not the same ting. Floor traders are selected in the most nonnarrative manner, just by evolution in the sense that nice arguments don’t make much difference.”

Perhaps I'm being a bit harsh focusing on an analogy but I think there might be a wider point. Producing the right or wrong answers in one domain isn't necessarily a useful predictor of someone's ability to produce the right or wrong answer in another - even when they are highly connected.

Comment author: Eliezer_Yudkowsky 29 July 2015 08:27:14PM 5 points [-]

"Does somebody being right about X increase your confidence in their ability to earn excess returns on a liquid equity market?" has to be the worst possible question to ask about whether being right in one thing should increase your confidence about them being right elsewhere. Liquid markets are some of the hardest things in the entire world to outguess! Being right about MWI is enormously being easier than being right about what Microsoft stock will do relative to the rest of S&P 500 over the next 6 months.

There's a gotcha to the gotcha which is that you have to know from your own strength how hard the two problems are - financial markets are different from, e.g., the hard problem of conscious experience, in that we know exactly why it's hard to predict them, rather than just being confused. Lots of people don't realize that MWI is knowable. Nonetheless, going from MWI to Microsoft stock behavior is like going from 2 + 2 = 4 to MWI.

Comment author: Lumifer 29 July 2015 08:34:49PM 2 points [-]

Lots of people don't realize that MWI is knowable.

What do you mean, "knowable"?

Showing that MWI is correct while other interpretations are not is straight-up Nobel material.

Comment author: Vaniver 30 July 2015 02:45:23PM *  1 point [-]

Showing that MWI is correct while other interpretations are not is straight-up Nobel material.

I don't think "MWI" is a useful abbreviation (unless you unpack it as "many world interpretations" it implies it's singular, for example), and I'm not sure "correct" is the right word either. My understanding of Eliezer's argument is like so:

  1. Interpretations of QM differ in how many postulates they have, and how difficult those postulates are to justify, but typically not in verifiable experimental predictions. (An interpretation that gets experimental predictions wrong should be dropped out of the running.)

  2. One should have higher credence in simpler interpretations--that is, ones with fewer and less strange postulates.

  3. The first major interpretation of QM adopted by mainstream science had additional costly postulates relative to later interpretations or the agnostic interpretation. That it is still taken seriously is evidence for the strength of first mover effects / the inadequacy of scientific philosophy in getting answers correct quickly.

  4. We know from superposition that many quantum phenomena are better described by "branch both ways" than "branch one way xor the other," and supposing that the other branch is deleted rather than inaccessible requires an extra postulate, which should lower our credence in interpretations that have only one surviving world.

I don't think this argument implies that there is a unique surviving interpretation--but it will never be the case that there is a unique surviving interpretation, because I can take that interpretation and add an unobservable feature to it, creating a new interpretation. The principle by which those interpretations are reduced in prominence, when applied straightforwardly to QM, suggests that it's more likely that other branches of the wavefunction that we are not on continue to exist rather than disappearing because we are not there.

(Personally, I still identify with "shut up and calculate," where one refuses to answer statements about whether or not the other branches are real. But if one must conclude something, it's less jarring to conclude they are real than unreal.)

Comment author: Lumifer 30 July 2015 03:32:25PM 0 points [-]

That all sounds very reasonable -- though I'm not as big a fan of William of Ockham as many people here -- but I still don't understand what did Eliezer mean by "knowable".

In the absence of a straightforward empirical interpretation ("knowable" = pokable, measurable, analysable...), I associate this word with mushy theology (along the "Christ is knowable through your heart" lines).

Comment author: Vaniver 30 July 2015 04:38:24PM *  2 points [-]

I still don't understand what did Eliezer mean by "knowable".

It's one thing to say "there are multiple competing interpretations," another to say "there is a simplest interpretation, and other, more burdensome variants," and still another to be able to point to the calculations that determine which explanation is simplest. I don't poll people on their interpretations of QM, but I am of the impression that many people who have opinions on QM interpretations aren't even aware that there's math that is useful for comparing interpretations. (Hence them not realizing that it's "knowable.")

There's also the point about lightness, and using the most likely explanation as the default explanation, instead of saying "sure, it's more likely, but not so much more likely enough that my pet theory is totally unacceptable in comparison, so I'm sticking with my pet theory."

Comment author: Lumifer 30 July 2015 05:04:21PM *  2 points [-]

aren't even aware that there's math that is useful for comparing interpretations

Notably, that "math" (and it's not just math) did not convince large chunks of the physics community -- people who are quite comfortable with numbers and who certainly know the "knowable" issue.

But this is an endless debate and it probably would be best not to step into the morass :-)

Comment author: Jacobian 29 July 2015 08:29:23PM 0 points [-]

Upvoted for criticizing the actual point :)

I agree that Bob is probably a weak analogy because who knows how stock-pickers actually pick stocks? I hope I didn't construct a reverse intuition pump. Still, Eliezer's job is either a research mathematician or a philosopher of epistemology, depending on what matters to you. Both those jobs depend quite a bit on getting the rules of probability right. I think disagreeing with Eliezer on the rules of probability isn't something one can ignore.

You also hit an important point with the question: is Bob a quant researcher? Or more specifically, what's his epistemology in each domain? A few years ago I met Robert Aumann, everyone's favorite theist-mathematician. It's clear to me that Aumann has separate epistemologies for claims about God, Israeli politics and game theory. I read his book about games with incomplete information, he actually goes to the trouble of writing out every single proof, it never says "God told me this is the upper bound". If Aumann tells me "I've proven with rigorous math than an AI boxing system is possible", I sit up and pay attention. If he tells me "AIs don't have souls so humans will always be superior" I won't take that argument seriously.

Eliezer claims and seems to have a single epistemology (EWOR) that he applies to all domains. Because of that, his accuracy in one domain directly reflects on the dependability of EWOR, and thus on his accuracy in other domains.