Right: in fact he would act as though MWI is certainly false... or at least as though Quantum Immortality is certainly false, which has a good chance of being true given MWI.

If all interpretations are equivalent with respect to testable outcomes, what makes the belief in any particular interpretation so important? Ease of intuitive understanding is a dangerous criterion to rely on, and a relative thing too. Some people are more ready to accept mental gymnastic than existence of another worlds.

I'm (yet) not convinced.

First, the links say that MWI needs a linear quantum theory, and lists therefore the linearity among its predictions. However, linearity is a part of the quantum theory and its mathematical formalism, and nothing specific to MWI. Also, weak non-linearity would be explicable using the language of MWI saying that the different worlds interact a little. I don't see how testing the superposition principle establishes MWI. A very weak evidence at best.

Second, there is a very confused paragraph about quantum gravity, which, apart from linking to itself, states only that MWI requires gravity to be quantised (without supporting argument) and therefore if gravity is successfully quantised, it forms evidence for MWI. However, nobody doubts that gravity has to be quantised somehow, even hardcore Copenhageners.

The most interesting part is that about the reversible measurement done by an artificial intelligence. As I understand it, it supposes that we construct a machine which could perform measurements in reversed direction of time, for which it has to be immune to quantum decoherence. It sounds interesting, but is also suspicious. I see no way how can we get the information into our brains without decoherence. The argument apparently tries to circumvent this objection by postulating an AI, which is reversible and decoherence-immune, but the AI will still face the same problem when trying to tell us the results. In fact, postulating the need of an AI here seems to be only a tool to make the proposed experiment more obscure and difficult to analyse. We will have a "reversible AI", therefore miraculously we will detect differences between Copenhagen and MWI.

However, at least there is a link to Deutsch's article which hopefully explains the experiment in greater detail, so I will read it and edit the comment later.

None of the tests in that FAQ look to me like they could distinguish MWI from MWI+worldeater. The closest thing to an experimental test I've come up with is the following:

Flip a quantum coin. If heads, copy yourself once, advance both copies enough to observe the result, then kill one of the copies. If tails, do nothing.

In a many-worlds interpretation of QM, from the perspective of the experimenter, the coin will be heads with probability 2/3, since there are two observers in that case and only one if the coin was tails. In the single-world case, the coin will be heads with probability 1/2. So each time you repeat the experiment, you get 0.4 bits of evidence for or against MWI. Unfortunately, this evidence is also non-transferrable; someone else can't use your observation as evidence the same way you can. And getting enough evidence for a firm conclusion involves a very high chance of subjective death (though it is guaranteed that exactly one copy will be left behind). And various quantum immortality hypotheses screw up the experiment, too.

So it is testable in principle, but the experiment involved more odious than one would imagine possible.

To be clear, if sentence X about goodness is translated into sentence Y about life and happiness etc., does sentence Y contain the word "good"?

Edit: What's left of religion after you make the queerness go away? Why does there seem to be more left of morality?

You might have gotten confused because I quoted Psy-Kosh's phrase "specific algorithm/dynamic for judging values" whereas Eliezer's original idea I think was more like an algorithm for changing one's values in response to moral arguments. Here are Eliezer's own words:

I would say, by the way, that the huge blob of a computation is not just my present terminal values (which I don't really have - I am not a consistent expected utility maximizers); the huge blob of a computation includes the specification of those moral arguments, those justifications, that would sway me if I heard them.

It is a common thesis here that most humans would ultimately have the same moral judgments if they were in full agreement about all factual questions and were better at reasoning. In other words, human brains have a common moral architecture, and disagreements are at the level of instrumental, rather than terminal, values and result from mistaken factual beliefs and reasoning errors.

It is? That's a worry. Consider this a +1 for "That thesis is totally false and only serves signalling purposes!"

Now this is a startling claim.

(you'll get to the arguments regarding that if you're reading the sequences)

Be more specific!

It is a common thesis here that most humans would ultimately have the same moral judgments if they were in full agreement about all factual questions and were better at reasoning.

Maybe it's true if you also specify "if they were fully capable of modifying their own moral intuitions." I have an intuition (an unexamined belief? a hope? a sci-fi trope?) that humanity as a whole will continue to evolve morally and roughly converge on a morality that resembles current first-world liberal values more than, say, Old Testament values. That is, it would converge, in the limit of global prosperity and peace and dialogue, and assuming no singularity occurs and the average lifespan stays constant. You can call this naive if you want to; I don't know whether it's true. It's what I imagine Eliezer means when he talks about "humanity growing up together".

This growing-up process currently involves raising children, which can be viewed as a crude way of rewriting your personality from scratch, and excising vestiges of values you no longer endorse. It's been an integral part of every culture's moral evolution, and something like it needs to be part of CEV if it's going to actually converge.

It is a common thesis here that most humans would ultimately have the same moral judgments if they were in full agreement about all factual questions and were better at reasoning.

That's not plausible. That would be some sort of objective morality, and there is no such thing. Humans have brains, and brains are complicated. You can't have them imply exactly the same preference.

Now, the non-crazy version of what you suggest is that preferences of most people are roughly similar, that they won't differ substantially in major aspects. But when you focus on detail, everyone is bound to want their own thing.

Psy-Kosh:

(of course, the notion that most humans seem to have the same underlying core "morality algorithm", just disagreeing on the implications or such, is something to discuss, but that gets us out of executive summary territory, no?)

I would say that it's a crucial assumption, which should be emphasized clearly even in the briefest summary of this viewpoint. It is certainly not obvious, to say the least. (And, for full disclosure, I don't believe that it's a sufficiently close approximation of reality to avoid the problem I emphasized above.)

The grey goo example was named to exemplify the speed and sophistication of nanotechnology that would have to be around to either allow an AI to be build in the first place or be of considerable danger.

I consider your comment an expression of personal disgust. No way you could possible misinterpret my original point and subsequent explanation to this extent.