"it" isn't a single theory.

The argument that Everettian MW is favoured by Solomonoff induction, is flawed.

If the program running the SWE outputs information about all worlds on a single output tape, they are going to have to be concatenated or interleaved somehow. Which means that to make use of the information, you gave to identify the subset of bits relating to your world. That's extra complexity which isn't accounted for because it's being done by hand, as it were..

By far the best definition I’ve ever heard of the supernatural is Richard Carrier’s: A “supernatural” explanation appeals to ontologically basic mental things, mental entities that cannot be reduced to nonmental entities.

Physicalism, materialism, empiricism, and reductionism are clearly similar ideas, but not identical. Carrier's criterion captures something about a supernatural ontology, but nothing about supernatural epistemology. Surely the central claim of natural epistemology is that you have to look...you can't rely on faith , or clear ideas implanted in our minds by God.

it seems that we have very good grounds for excluding supernatural explanations a priori

But making reductionism aprioristic arguably makes it less scientific...at least, what you gain in scientific ontology, you lose in scientific epistemology.

I mean, what would the universe look like if reductionism were false

We wouldn't have reductive explanations of some apparently high level phenomena ... Which we don't.

I previously defined the reductionist thesis as follows: human minds create multi-level models of reality in which high-level patterns and low-level patterns are separately and explicitly represented. A physicist knows Newton’s equation for gravity, Einstein’s equation for gravity, and the derivation of the former as a low-speed approximation of the latter. But these three separate mental representations, are only a convenience of human cognition. It is not that reality itself has an Einstein equation that governs at high speeds, a Newton equation that governs at low speeds, and a “bridging law” that smooths the interface. Reality itself has only a single level, Einsteinian gravity. It is only the Mind Projection Fallacy that makes some people talk as if the higher levels could have a separate existence—different levels of organization can have separate representations in human maps, but the territory itself is a single unified low-level mathematical object. Suppose this were wrong.

Suppose that the Mind Projection Fallacy was not a fallacy, but simply true.

Note that there are four possibilities here...

1. I assume a one level universe, all further details are correct.

2. I assume a one level universe, some details may be incorrect

3. I assume a multi level universe, all further details are correct.

4. I assume a multi level universe, some details may be incorrect.

How do we know that the MPF is actually fallacious, and what does it mean anyway?

If all forms of mind projection projection are wrong, then reductive physicalism is wrong, because quarks, or whatever is ultimately real, should not be mind projected, either.

If no higher level concept should be mind projected, then reducible higher level concepts shouldn't be ...which is not EY's intention.

Well, maybe irreducible high level concepts are the ones that shouldn't be mind projected.

That certainly amounts to disbelieving in non reductionism...but it doesn't have much to do with mind projection. If some examples of mind projection are acceptable , and the unacceptable ones coincide with the ones forbidden by reductivism, then MPF is being used as a Trojan horse for reductionism.

And if reductionism is an obvious truth , it could have stood on its own as apriori truth.

Suppose that a 747 had a fundamental physical existence apart from the quarks making up the 747. What experimental observations would you expect to make, if you found yourself in such a universe?

Science isn't 100% observation,it's a mixture of observation and explanation.

A reductionist ontology is a one level universe: the evidence for it is the success of reductive explanation , the ability to explain higher level phenomena entirely in terms of lower level behaviour. And the existence of explanations is aposteriori, without being observational data, in the usual sense. Explanations are abductive,not inductive or deductive.

As before, you should expect to be able to make reductive explanations of all high level phenomena in a one level universe....if you are sufficiently intelligent. It's like the Laplace's Demon illustration of determinism,only "vertical". If you find yourself unable to make reductive explanations of all phenomena, that might be because you lack the intelligence , or because you are in a non reductive multi level universe or because you haven't had enough time...

Either way, it's doubtful and aposteriori, not certain and apriori.

If you can’t come up with a good answer to that, it’s not observation that’s ruling out “non-reductionist” beliefs, but a priori logical incoherence"

I think I have answered that. I don't need observations to rule it out. Observations-rule it-in, and incoherence-rules-it-out aren't the only options.

People who live in reductionist universes cannot concretely envision non-reductionist universes.

Which is a funny thing to say, since science was non-reductionist till about 100 years ago.

One of the clinching arguments for reductionism.was the Schrödinger equation, which showed that in principle, the whole of chemistry is reducible to physics, while the rise of milecular biology showeds th rreducxibility of Before that, educators would point to the de facto hierarchy of the sciences -- physics, chemistry, biology, psychology, sociology -- as evidence of a multi-layer reality.

Unless the point is about "concretely". What does it mean to concretely envision a reductionist universe? Pehaps it means you imagine all the prima facie layers, and also reductive explanations linking them. But then the non-reductionist universe would require less envisioning, because byit's the same thing without the bridging explanations! Or maybe it means just envisioing huge arrays of quarks. Which you can't do. The reductionist world view , in combination with the limitations of the brain, implies that you pretty much have to use higher level, summarised concepts...and that they are not necessarily wrong.

But now we get to the dilemma: if the staid conventional normal boring understanding of physics and the brain is correct, there’s no way in principle that a human being can concretely envision, and derive testable experimental predictions about, an alternate universe in which things are irreducibly mental. Because, if the boring old normal model is correct, your brain is made of quarks, and so your brain will only be able to envision and concretely predict things that can predicted by quarks.

1. "Your brain is made of quarks" is aposteriori, not apriori.

2. Your brain being made of quarks doesn't imply anything about computability. In fact, the computatbolity of the ultimately correct version of quantum physics is an open question.

3. Incomputability isn't the only thing that implies irreducibility, as @ChronoDas points out.

4. Non reductionism is conceivable, or there would be no need to argue for reductionism.

Unionism sound like two things pretending to be one thing. Does "blend" mean we get more of their vaklues, or they get more of ours? I'm reminded of company mergers, where the smaller company basically ends up getting eaten, despite initial promises to the contrary.

As a guiding intuition, consider the case of white light, which was regarded as an intrinsic property of nature until Newton discovered that it is in fact composed of seven distinct colours. White light is an illusion in the sense that it does not possess an intrinsic property “whiteness” (even though it seems to). Suppose we manage to explain, with a high degree of precision, exactly how and when we perceive white, and why we perceive it the way we do. We do not subsequently need to formulate a “hard problem of whiteness” asking why, on top of this, whiteness arises. Illusionists claim that consciousness is an illusion in the same sense that whiteness is.[1]

What the explanation of white would be analogous to, if it existed, is a solution to the Hard Problem, in its own terms -- an explanation of phenomenal consciousness, that doesn't dismiss consciousness. Because the explanation of white light doesn't tell you that there is no such thing, it just tells you that it is made of parts, non fundamental. (Confusion between reduction and elimination is rife).

White light isn't a good example of an illusion: rainbows would be better.

There would be no need for a Hard Problem if there were no prima facie evidence for phenomenality ... but there is. If there were not, there would be no need to explain away as an illusion.

So illusionists don’t deny that conscious experiences exist in some sense (we’re talking about them right now!). They deny that conscious experiences have a special kind of property: phenomenality (although they really seem to have phenomenality

Which means they have phenomenality, unless the seeming is cashed out in entirely cognitive terms.

The most common objection to illusionism is straightforward: how can consciousness be an illusion when I obviously feel pain

No the most common objection is that it is self defeating, in that it needs to appeal to one kind of phenomenally "quasi phenomenality" to explain away another.

Illusionism basically says this: once we have successfully explained all our reports about consciousness, there will be nothing left to explain.

But illusionism has no argument that it's inevitable that reports will be reports of intrinsically subjective phenomena. Illusionist argument s always boil down to possibility.

There is little reason to expect evolution to enforce that our reports be correct

@Adele Lopez

that it is more about phenomenal consciousness being non-representational—meaning something like that it has the type signature of a world-model without actually being a model of anything real (including itself).

That might be a more accurate version of what illusionists actually think, but it's still incredible. If course phenomenal consciousness is a model of the outside world: testable rd presents certain frequencies of light, and so on.

If what the thalamus is doing is decision making (conscious or unconscious), it could be expressed as such.

Unconscious decision making is a thing.

it’s kinda difficult to decide what the concept of free will means

But it's possible to divide and conquer . to treat specific meanings separately, for instance, compatibilist and libertarian free will.

Different definitions of free will require freedom from different things. Much of the debate centres on Libertarian free will, which requires freedom from complete causal determinism (an therefore, freedom from inevitability) Compatibilist definitions of free will only require freedom from compulsion, and allow free will to exist in a deterministic universe. Sam Harris believes free will is a form of conscious control.

Libertarian free will has sub-varieties. One is "contra causal" free will, which requires freedom from physics, on the assumption that physics is deterministic. This is often connected with the idea of a supernatural soul, that is able to override the physics of the brain. In contrast, naturalistic libertarians seek to find free will within physics, by rejecting physical determinism; they regard indeterminism as a necessary (but perhaps not sufficient) condition of free will

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Yudkowsky considers the problem of free will to be easy, in contrast to professional philosophers. He believes that he has dissolved the problem, that is, shown that it never was a problem, that it's all based on a confusion. However, his solution ultimately sides with compatibilism and against libertarianism.

He rejects dualism , insisting "Thou Art Physics", a claim which only directly contradicts supernatural, contra-causal libertarianism. Physics is not known to be deterministic, so Thou Art Physics doesn't exclude libertarian free will via the usual route of removing "elbow room" , or "could have done otherwise".

He proposes a theory where the feeling of libertarian free will is explained naturaliststically, as an illusion, without the existence of an actual power of free will. But it is also possible to construct theories of non-magical ,non-dualistic free will, such as Robert Kane's naturalistic libertarianism. Such theories also account for the existence of a quale of free will, but this time as a accurate perception of a real ability. So Yudkowsky has an explanation, not the only possible one .... his solution is example of an a/the fallacy.

If he had an argument for determinism on top of physicalism, he could close the loophole and exclude naturalistic libertarianism as well as supernaturalistic libertarianism. Instead, he ignores the possibility.

Note that naturalistic libertarianism relies on physical indeterminism. Since indeterminism. . is not known to be true, it could turn out to be unworkable on evidence of determinism...but physical indeterminism is still a respectable naturalistic hypothesis that doesn't require ghosts or magic.

How would particles or humans behave differently if they had free will compared to if they didn’t

Indeterminism is a component of naturalistic libertarian free will , and indeterministic behaviour in particles is detectable. (See Bell's inequalities and the Aspect experiment). Fundamental indeterminism probably isn't sufficient for free will, but the other components of NLFW, such as specific neural mechanisms, are testable - they would hardly be naturalistic otherwise!

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Yudkowsky also claims that determinism is required for free will. Requiredism holds that determinism is an advantage to fee will because the connection between a decision and the resulting action is deterministic.

But we have no evidence of a 100% 'reliable connection between thought and action, so strict determinism is not necessary for the kind of decision making we observe that n ourselves-- it's overkill.

Randomness, or at least, too much randomness in the wrong place, would prevent me from acting reliably on my decisions Of course, determinism also removes the elbow room, the the ability to have decided differently, that is of such concern to libertarians -- that is, to them, the "free" in "free will'.Determinism is only an overall advantage to free will if elbow room is unimportant or impossible, so requiredism needs compatibilism as a starting point. -- hence its other name, supercompatibilism.

In recent years it has become very clear that the thalamus is vitally important in consciousness and very arguably is the seat of consciousness

In which sense? Wakefulness? attention? Phenomenality? Self representation?

Responding at the object level and not responding at all aren't the only options. You can respond by saying you are not going to reply further, because the comment was a gish gallop, derailment, or whatever.

can’t distinguish between hypotheses without assuming simplicity as an axiom (which, feel free to do so, but I already argued it doesn’t need to be assumed).

So have I.:-

There are more complex conjectures than simple ones. So if you conjecture something complex, it is less likely to be the right conjecture. Also, you have only a finite amount of time to consider conjectures, so you can’t start at the end an infinite list..But you can start with th the simplest conjecture. Of course, that’s roughly how Solomonoff induction works.

(Also, it is completely unclear why "having to assume simplicity" amounts to "not working". You could argue, as Vasrani does that Bayes without simplicity doesn't work: I have argued that no real Bayesian ignores simplicity).

but that’s not what I was arguing against

Why not? An aircraft without wing s or engine is sim ple, but it can't fly.

Okay, well that’s a bit of a bedrock of disagreement then

Because you think I was stipulating something else? Because you think there are no simple inductors?

Sure, so what is your sufficient condition for conjecture to be present, and what is your necessary condition for induction to be present

You can tell that a algorithm is making predictions on a black box basis , and you can tell it's an inductor if it does immediately on boot up.

A conjecture-and-refutation machine has to be complex enough to form high level representations, and make inferences from them.