if you manage to get yourself stuck in an advanced rut, dutifully playing Devil's Advocate won't get you out of it.

It's not a binary either/or proposition, but a spectrum; you can be in a sufficiently shallow rut that a mechanical rule of "when reasoning, search for evidence against the proposition you're currently leaning towards" might rescue you in a situation where you would otherwise fail to come to the correct conclusion. That said, yes, it would indeed be preferable to conduct the search because you actually have "true doubt" and lack overconfidence, rather than by rote, and rather than for the odd reasons that Michael Rose gives.

Dad was an avid skeptic and Martin Gardner / James Randi fan, as well as being an Orthodox Jew. Let that be a lesson on the anti-healing power of compartmentalization

Why do you think that, if he had not compartmentalized, he would have rejected Orthodox Judaism, rather than rejecting skepticism?

"Oh, look, Eliezer is overconfident because he believes in many-worlds."

I can agree that this is absolutely nonsensical reasoning. The correct reason to believe Eliezer is overconfident is because he's a human being, and the prior that any given human is overconfident is extremely large.

One might propose heuristics to determine whether person X is more or less overconfident, but "X disagrees strongly with me personally on this controversial issue, therefore he is overconfident" (or stupid or ignorant) is the exact type of flawed reasoning that comes from self-serving biases.

Some physicists speak of "elegance" rather than "simplicity". This seems to me a bad idea; your judgments of elegance are going to be marred by evolved aesthetic criteria that exist only in your head, rather than in the exterior world, and should only be trusted inasmuch as they point towards smaller, rather than larger, Kolmogorov complexity.

Example:

In theory A, the ratio of tiny dimension #1 to tiny dimension #2 is finely-tuned to support life.

In theory B, the ratio of the mass of the electron to the mass of the neutrino is finely-tuned to support life.

An "elegance" advocate might favor A over B, whereas a "simplicity" advocate might be neutral between them.

can you tell me why the subjective probability of finding ourselves in a side of the split world, should be exactly proportional to the square of the thickness of that side?

Po'mi runs a trillion experiments, each of which have a one-trillionth 4D-thickness of saying B but is otherwise A. In his "mainline probability", he sees the all trillion experiments coming up A. (If he ran a sextillion experiments he'd see about 1 come up B.)

Presumably an external four-dimensional observer sees it differently: He sees only one-trillionth of Po'mi coming up all-A, and the rest of Po'mi saw about 1 B and are huddled in a corner crying that the universe has no order. (Maybe the 4D observer would be unable to see Po'mi at all because Po'mi and all other inhabitants of the lawful "mainline probablity" that we're talking about have almost infinitesimal thickness from the 4D observer's point of view.)

If I were Po'mi, I would start looking for a fifth dimension.

It seems worthwhile to also keep in mind other quantum mechanical degrees of freedom, such as spin

Only if the spin's basis turns out to be relevant in the final ToEILEL (Theory of Everything Including Laboratory Experimental Results) that gives a mechanical algorithm for what probabilities I anticipate.

In contrast, if someone had a demonstrably-correct theory that could tell you the macroscopic position of everything I see, but doesn't tell you the spin or (directly) the spatial or angular momentum, then the QM Measurement Problem would still be marked "completely solved". In such a position-basis theory, the answer to any question about spin would be "Mu, it only matters if it affects the position of my macroscopic readout."

Robin: is there a paper somewhere that elaborates this argument from mixed-state ambiguity?

Scott should add his own recommendations, but I would say here is a good starting introduction.

To my mind, the fact that two different situations of uncertainty over true states lead to the same physical predictions isn't obviously a reason to reject that type of view regarding what is real.

The anti-MWI position here is that MWI produces different predictions depending on what basis is arbitrarily picked by the predictor; and that the various MWI efforts to "patch" this problem without postulating a new law of physics, are like squaring the circle. I think the anti-MWI'ers math is correct, but I'm not an expert enough to be 100% sure; what *really* makes me think MWI is wrong is the inability of the MWI'ers, after many decades, to produce an *algorithm* that you can "turn the crank" on to get the correct probabilities that we see in experiments; they have the tendency of trying to patch this "basis problem" by producing a new framework, which itself contains an arbitrary choice that's just as bad as the arbitrary choice of basis.

More succinctly, in vanilla MWI you have to pick the correct basis to get the correct experimental results, and you have to peek at the results to get the correct basis.

In many of your prior posts where you bring up MWI, your interpretation doesn't fundamentally matter to the overall point you're trying to make in that post; that is, your overall conclusion for that post held or failed regardless of which interpretation is correct, possibly to a greater degree than you tend to realize.

For example: "We used a true randomness source - a quantum device." The philosophers' point could equally have been made by choosing the first 2^N digits of pi and finding they correspond by chance to someone's GLUT.

the colony is in the future light cone of your current self, but no future version of you is in its future light cone.

Right, and if anyone's still confused how this is possible: wikipedia and a longer explanation

* That-which-we-name "consciousness" happens within physics, in a way not yet understood, just like what happened the last three thousand times humanity ran into something mysterious.

*not yet* understood? Is your position that there's a mathematical or physical discovery waiting out there, that will cause you, me, Chalmers, and everyone else to slap our heads and say, "of course, that's what the answer is! We should have realized it all along!"

Question for all: How do you apply Occam's Razor to cases where there are two competing hypotheses:

1. A and B are independently true

2. A is true, and implies B, but in some mysterious way we haven't yet determined. (For example, "heat is caused by molecular motion" or "quarks are caused by gravitation", to pick two inferences at opposite ends of the plausibility spectrum.)

I don't know what the best answer is. Maybe the practical answer is a variant of Solomoff induction: somehow compare "P(A) * P(B)" with "P(A) * P(B follows logically from A, *and* we were too dumb to realize that)", where the P's are some type of Solomonoff-ish a-priori "2^shortest program" probabilities. But the best answer certainly isn't, "A is simpler than A + B, so we know hypothesis 2 is correct, without even having to glance at the likelihood that B follows from A." Otherwise, you would have to conclude that, logically, quarks are caused by gravitation, in some currently-mysterious way that future mathematicians will be certain to discover.

For the record, my belief is that many of the debaters have beliefs that are isomorphic to their opponent's beliefs. When I hear things like, "You said this is a physical law without material consequences, but I define physical laws as things that have material consequences, so you're wrong QED!" then that's a sign that we're in "does a tree falling in the forest make a noise" territory. Does a conciousness mapping rule "actually exist"? Does the real world "actually exist"? Does pi "actually exist"? Why should I care?

In the end, I care about actions and outcomes, and the algorithms that produce those actions. I don't care whether you label conciousness as "part of reality" (because it's something you observe), or "part of your utility function" (because it's not derivable by an intelligence-in-general), or "part of this complete nutritious breakfast" (because, technically, anything that's not poisonous can be combined with separate unrelated nutritious items to form a complete nutritious breakfast.)

@spindizzy:

No, this hasn't been "argued out", and even if it had been in the past, the "single best answer" would differ from person to person and from year to year. I would suggest starting a thread on SL4 or on SIAI's Singularity Discussion list.