It's a pity I consider my current utility function bounded; the statement "there's no amount of fun F such that there isn't a greater amount of fun G such that I would I would prefer a 100% chance of having fun F, to having a 50% chance of having fun G and a 50% chance of having no fun" would have been a catchy slogan for my next party.

The difficulty with analyzing the "insightfulness quotient" of comedians like Scott Adams or Jon Stewart is that there's no reliable way of differentiating "things he sincerely believes" versus "things he means seriously at some level, but are not literally true" versus "things that are meant to be just throwaway jokes". If you're sympathetic to Scott Adams, you're likely to interpret true statements or true predictions as "hits", but classify false predictions as "just jokes", and overestimate how insightful he is on average.

Which begs the question, why bother to seek insights from Scott Adams in the first place, if he deliberately mixes in false or misleading statements in with true statements. There are already enough "unwittingly false" statements in the media to keep us on our toes in the first place.

Another solid article.

One point of confusion for me: You talk about axiomatic *faith* in *logic* (which is necessary in some form to bootstrap your introspective thinking process), but then abruptly switch to talking about "the last ten million times that first-order arithmetic has proven consistent", a statement of *observed prior evidence* about *learned arithmetic*. Both points are valid, but it seemed a non sequiter to me to abruptly go from one to the other.

Oh well, off to cast half a vote in the Michigan Primary.

Rolf, surely the simplicity of MWI relative to objective collapse is strong evidence that when we have a better technical understanding of decoherence it will be compatible with MWI?

What do you mean by "compatible"? Do you mean, the observed macroscopic world will emerge as "the most likely result" from MWI, instead of some other macroscopic world where objects decohere on alternate Thursdays, or whenever a proton passes by, or stay a homogeneous soup forever? That's a *lot* of algorithmic bits that I have to penalize MWI for, given that this has not been demonstrated.

Here's the linchpin of my argument: why should I believe, a priori, that the observed macroscopic world has a decent chance of popping naturally out of MWI, any more than I should believe that the observed world might pop out from the philosophy "All Is Fire?" Should I believe this just because some people have convinced themselves that it probably does (even if they consistently fail to demonstrate it in a rigorous way?) But such post-hoc intuitive beliefs are notoriously unreliable. Extreme example: many people believe that quantum mechanics emerges naturally from Buddhist beliefs (yet, again, oddly they cannot demonstrate this in a rigorous way, and as an added coincidence, they only started saying this *after* quantum mechanics had already been discovered by secular experimentation.)

Aside: if MWI'ers had *started* in 1890, and then used their "simple MWI" theory to go *backwards* from macroscopic observations to infer the possible existence of quantum mechanics by asking themselves "from what sets of simple theories might the macroscopic world naturally and intuitively emerge", now *that* would have impressed me.

Do you have any specific problem in mind? Have you read some of the post-2000 papers on how MWI works, like Everett and Structure?

From the paper:

Two sorts of objection can be raised against the decoherence approach to definiteness. The first is purely technical: will decoherence really lead to a preferred basis in physically realistic situations, and will that preferred basis be one in which macroscopic objects have at least approximate definiteness. Evaluating the progress made in establishing this would be beyond the scope of this paper, but there is good reason to be optimistic. The other sort of objection is more conceptual in nature: it is the claim that even if the technical success of the decoherence program is assumed, it will not be enough to solve the problem of indefiniteness...

So David Wallace would agree that "decoherence for free", mapping QM onto macroscopic operations without postulating a new non-unitary rule, has not yet been established on that tiny little, nitpicky "purely technical" level. The difference is that Wallace presumably believes that success is Right Around the Corner, whereas I believe the 50 years of failure are strong evidence that the basic approach is entirely wrong. (And yes, I feel the same way about 20 years of failure in String Theory.) Time will tell.

I wish to hell that I could just not bring up quantum physics. But there's no real way to explain how reality can be a perfect mathematical object and still look random due to indexical uncertainty, without bringing up quantum physics.

MWI doesn't explain why the Universe has four large dimensions and three small neutrinos. In order to explain that by indexical uncertainty, you have to bring up other multiverse concepts anyway, and if you bring in "ultimate ensemble" theories, then MWI vs. non-MWI no longer matters for the rhetorical point you're making.

I am personally unconvinced by the arguments that MWI does away with the need for a non-unitary operation, because of the inability of MWI proponents to show that MWI works in a rigorous way without one. I would bet that some combination of Objective Reduction + MWI is the correct physical theory. The point I'm trying to make is that the Eliezer's conclusion about indexical uncertainty may still be correct, even if you find Everett's MWI incoherent.

Doug S., I believe according to quantum mechanics the smallest unit of length is Planck length and all distances must be finite multiples of it.

Not in standard quantum mechanics. Certain of the many theories unsupported hypotheses of quantum gravity (such as Loop Quantum Gravity) might say something similar to this, but that doesn't abolish every infinite set in the framework. The total number of "places where infinity can happen" in modern models has tended to increase, rather than decrease, over the centuries, as models have gotten more complex. One can never prove that nature isn't "allergic to infinities" (the skeptic can always claim, "wait, but if we looked even closer or farther, maybe we would see a heretofore unobserved brick wall"), but this allergy is not something that has been empirically observed.

Is there a word for the similar case to the "just-so" story, but that has a spurious environmental explanation rather than a spurious genetic explanation? (For example, "boys are more aggressive than girls because parents give their boys more violent toys.") I see many more of the former than the latter in the media.

I don't find the polls consistent with the picture of libertarian voters vs. colluding statist politicians. Only a significant majority (not an overwhelming majority) seems to support lower taxes, and when the question is phrased as costs vs. benefits (rather than "taxes in a vacuum") that majority tends to disappear.

the overreaction was foreseeable in advance, not just in hindsight

To paraphrase what my brain is hearing from you, Eliezer:

In 2001, you would have predicted, "In 2007, I will believe that the U.S. overreacted between 2001 and 2007."

In 2007, your prediction is true: you personally believe the U.S. overreacted.

Not very impressive. (I know lots of people who can successfully predict that they will have the same political beliefs six years from now, no matter what intervening evidence occurs between now and then! It's not something that you should take pride in. :-)

I would suggest you join a prediction market if you believe you have an uncanny, cross-domain knack for consistently predicting the future, except that I don't want to distract you from your AI work.