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> 4. I wonder if Carroll's future work in philosophy will cause him to revisit the many-worlds interpretation of QM, which a fair share of philosophers believe carries too much metaphysical baggage. The idea of many worlds "existing" is a philosophical idea; it's not something you learn from studying physics.

I think he would argue it carries the least metaphysical baggage as the worlds exist in the equations we have, unlike things posited by other interpretations.

That is exactly what he argues.

But I think it's a tough position, given that relational quantum mechanics also works "out of the box" and doesn't require ontological realism and a deeply speculative metaphysics.

Sean Carroll discusses this with Carlo Rovelli in two separate Mindscape episodes.

Interesting, I'll have to listen to that. Sounds pretty much like QBism though.

I don't grasp essential the difference between everettian and RQM.

I'm both cases different observers observe different results.

IIUC the "worlds" on the many worlds interpretation is just a convenient way to talk about the relationship between an observer and the possible states it can observe after the system and the observer have been entangled. The emergence of a world branch is not something that happens at some specific moment in time. This is also why branching can be viewed as happening at superluminal speeds, because it's not a physical phenomenon, just a shortcut for us to use to discard states that are no longer accessible to us.

Whether that makes the many worlds interpretation more useful or less useful, it's a matter of context. However I have the impression that most people who oppose the view (e.g. citing how much more baggage it requires etc) fundamentally come from the mental trap of thinking that a conscious observer had a unique stream of consciousness and that anything that deviates from it would be inconceivable because "we don't experience it"

What you describe with respect to many worlds sounds more like possible worlds semantics. Someone not committed to the view might treat it as a formalism with no metaphysical baggage, but I don't think that is what the endorsors of many worlds believe. Carroll certainly believes in a universal wave function and actual many worlds. And there is definitely a difference between RQM: https://plato.stanford.edu/entries/qm-relational/#CompOtheIn...

I am sympathetic to the idea that no one interpretation is 100% correct and that we shouldn't be deeply attached to any of them. Each may have its usefulness in different contexts. Independent of that, some interpretations more accurately describe the quantum world than others, surely.

This was my interpretation of Carroll's interpretation of the may worlds interpretation :-)

I'm an avid listener to mindscape podcast and read of his books, so I'm likely "indoctrinated", as I don't really know much of these things.

But I had the distinct impression that Carrol believes that all there is is the wave function of the universe and everything else (including the many worlds) are emergent phenomena. In a way many worlds are "real" in the same way that "chairs" are real.

In the paper, Carrol goes through great pains to try reject people changing the laws of physics because they don't understand consciousness. This is exactly how I view people taking up the Copenhagen interpretation of quantum mechanics, where the wave function of the entire universe collapses when a random person makes an observation. Instead I take Schrodinger's equation (and the many worlds interpretation) as the rule and what we observe illuminates how _we_ work, or more specifically how the brain and consciousness work.

> Most work in this area is unadulterated quackery

Citation needed: please say, exactly, to what or to whom you are referring.[0] In my experience with the study the work is precisely opposite of quackery: integrity, veracity, forthrightness.[1] My favorites are rivals Searle and Dennett, and though I believe Churchland(s) are incorrect, their work provides deep insight into brain and neurology for an excellent foundation for students of Philosophy of Mind. The point here is, even those that are incorrect (such as Descartes and other dualists) are not quacks: only through dissent do things move forward. Please give us examples of "quackery" in Philosophy of Mind. Because from where I am standing, any of them that rely on reductionism, which I expect a physicist would, are likely in error, because no matter how you slice up brain, you will never find mind.

[0] https://en.wikipedia.org/wiki/List_of_philosophers_of_mind [1] https://en.wikipedia.org/wiki/Philosophy_of_mind

But facts are only facts if they correspond with that to which they refer, oftentimes other objects, so when you include facts, ultimately it boils down to external objects.

I think you also failed to include Idealism, that the world's fundamental construction is of Reason. For the uninitiated or the naive, the notion of Idealism often degenerates in their minds to Solipsism, but it is far from that.

> But facts are only facts if they correspond with that to which they refer, oftentimes other objects, so when you include facts, ultimately it boils down to external objects.

Only if ontological questions are legitimate questions about the world and not simply practical decisions about language. I, and many others, remain unconvinced.

What judges whether an ontological question is legitimate or not? In order to ask such a question you are implying that there is something beyond the ontological questioner who can determine these things. What or who is this ultimate judge? God? A phantom? A unicorn? When you write "I, and many others, remain unconvinced" you are already under the assumption that you, and many others, can be this judge. And what is it about you, and many others, that can make this judgment? REASON!

On one level you bring forth an argument against my points about Idealism, but your implicit assumptions in your arguments bely your reliance on many of these same points that I brought up.