Sean Carrol explains why your objection about too many universes is "wrong headed" in his short article on why MWI is "probably correct". He uses the word "split" to describe what happens to two universes when there is an apparent collapse

>(“spin is up” + “spin is down” ; apparatus says “ready”) (1)

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>(spin is up ; apparatus says “up”) + (spin is down ; apparatus says “down”). (2)

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>We wouldn’t think of our pre-measurement state (1) as describing two different worlds; it’s just one world, in which the particle is in a superposition. But (2) has two worlds in it. The difference is that we can imagine undoing the superposition in (1) by carefully manipulating the particle, but in (2) the difference between the two branches has diffused into the environment and is lost there forever.

When you have a superposition of two states each state is it's own world.

>You’re just using the wrong language when referring to a collapse that’s all.

The only time I used the word collapse in the comment you're replying to is to say MWI's purpose is to explain apparent collapse. Saying it doesn't happen is still an explanation. You're getting tangled in the weeds with this one.

MWIs ‘explanation’ for collapse is that it doesn’t collapse. You’re just using the wrong language when referring to a collapse that’s all.

I’m still just not seeing anything that explains why all must exist at all times vs them beginning to exist only at a point in time. It’s just not intuitive to start from a position of a potentially infinite number of identical copies. I get why it’s neater from a conservation perspective because everything has its own energy already before docehering but I need to hear something that explains why that can’t be split at the moment of decoherence instead, with the pre-decohered state containing all of the energy within one world.

I think I’ll leave it here as if there were a clearer explanation for this it probably would have come out by now. But I at least understand the position so can ask the question.

All Ive been talking about is how beliefs are supported by evidence and I think thats how most people think. They change their minds if they feel that their beliefs are no longer supported by the evidence they see.

As for non-contradiction, I don't know. It seems an obvious part of my general thought the overwhelming majority of the time but I do understand there are people with views and who have created logics that are not so strict about that. I am open to logical pluralism and/or nihilism.

That’s existentialism.

>Each of these, at a point in time, having the same wave function as there’s no entanglement?

They are each a part of the same universal wave function. Of course they are entangled. If you know the outcome in one universe you know the outcome in the other.

>Both of these worlds exist in the same hilbert space as before, but they are now relatively ‘skinnier’.

Yes when they decohere they are "smaller" than when they are together. Nothing new is created two things that were coherent became two things that are decoherent. A division of existing space is not the creation of new space.

>So if you can explain why all worlds, which will ever feature every event of decoherence, always exist, in a succinct way, then I’ll put that to Sean as the point of debate and he can hopefully help me get it!

You're saying yourself that one "thick" thing becomes two "thinner" things. That isn't the creation of anything.

>It’s disconcerting that you’re using the language of collapse when talking about MWI

The entire point of MWI is to explain collapse.

You’re just mostly describing the basics of QM. That’s not the issue here. The topic is MWI and when the other worlds start existing. I already understand why they need to. It’s disconcerting that you’re using the language of collapse when talking about MWI as the wave function doesn’t collapse in MWI but I can just assume you’re describing the observation of our branch of the wave function after decoherence.

What you need to explain is why all of the many worlds must exist, all of which will be identical copies until their own event of decoherence happens. Each of these, at a point in time, having the same wave function as there’s no entanglement? It needs to be clear why it cannot be the case that we start from a position of one world, which then upon an event of decoherence, creates two worlds. Both of these worlds exist in the same hilbert space as before, but they are now relatively ‘skinnier’.

So if you can explain why all worlds, which will ever feature every event of decoherence, always exist, in a succinct way, then I’ll put that to Sean as the point of debate and he can hopefully help me get it!

My central tenet for justified belief is basically this: that the evidence we have (e.g. sensory or memory evidence) is a reasonable basis for belief.

This isn't because I think we can argue that the evidence is true, but because we don't have an alternate basis for logically interacting with the world. Our evidence is singular, and we can either accept it with some degree of doubt or we have no basis whatsoever. If we were to accept a skeptical hypothesis instead, then we would have to logically conclude that we have no evidence of the external world and no means of logically interacting with it. I don't know that my evidence is true or accurate (and in fact have good reason to think that at least some of it is untrue), but it's more reasonable for me to accept it ceteris paribus than it is to reject it.

For definitions of knowledge, I would recommend looking up knowledge in a philosophical source, such as the Stanford Encyclopedia of Philosophy. JTB is far from the only definition of knowledge, but it's the core of externalist conceptions of knowledge, which are generally more popular than internalist ones (which have their own issues, such as lack of grounding to reality or the possibility of false knowledge). I stuck with JTB because it's the simplest version and I didn't want to devote 50 pages to different forms of knowledge in this paper.

The clock problem itself comes from Russell's "Human Knowledge" and has been discussed fairly extensively as a proto-Gettier problem, largely as a criticism of JTB.

Let me try again then. Do me a favor and stop thinking about t=0 or when the universal wave function was created or when entropy started. Or even entropy at all. All of that is a separate and irrelevant question.

I don't want to source every sentence but if I say anything in the following comment that you don't accept then I would be happy to source it.

In quantum mechanics we have things called states. You can add, or superpose, any states together as much as you want. It's similar to how you can just add up waves and their interference. This sum of two states is called the superposition. Eventually though something in a superposition of more than one state will eventually interact with something causing it to resolve to one of it's base states. Unfortunately we cannot determine which state the superposition will collapse into. We can only describe it probabilistically.

We need to explain why this is and what happened to the other states. One solution is the Many Worlds Interpretation. In MWI the other states of the superposition don't just disappear. Instead, in another universe, the superposition resolved to the "lost" state.

Now notice how I said we need to explain where the "lost" state went? Well we need to explain it because the state existed before the collapse and we want to know where it went. The collapse of the superposition does not create a new universe and it does not create a new state. Instead these two states decohered from one another. Nothing new is created.

I’ve already asked if you can link to anything that can explain what is happening as I’m not connecting with your attempts to explain it and I can’t find anybody saying what you’re saying. I just get overwhelmed with physicists talking about instances of branching occurring over time. I don’t really see that you are making any points that I haven’t responded to but perhaps I’m also just not understanding those. The only questions of yours I ignored were ones I commented on previously and I’m not resorting to telling you to read more carefully for failing to address half of my previous comment, so you can keep that kinda language to yourself.

I tell you what, I’ll ask Sean Carroll in a couple of weeks and will get him to explain his view. I’ll write back and link you his response then and maybe that will help me understand and help you explain it better.

Edit: Some of your post appeared after I responded, dunno if you edited but doesn’t matter. Just wanted to say I don’t know why you talk down to me with stuff like ‘that’s called determinism’, like yeah, I know, I literally used the word determined in the quote. You did the same thing before where you tell me my understanding of the full universe is wrong only to agree with me and tell me that’s what you said. It makes me view you as a lot less credible.

We don't even know that there was a t=0 and if there was we don't know what it was like. It's ridiculous to make these assumptions about t=0. Also there was almost certainly entropy at t=0. Entropy is a property of system so unless the universe wasn't a system at t=0 it had a value for it's entropy.

>If what you’re saying was correct the language should be that those universes already have been

I said the electrons will be created not the universes. You need to read my comments more carefully and consider answering my questions. Repeatedly shoving the word branching into your comment doesn't show that universes are being created. You're arguing about physics using a third hand analogy and are fixating on the word branching because you don't understand what's happening. It's like two people(universes) holding hands(coherent) taking different paths(decohering). No new person was created the two people just followed the same path until the branch.

> interaction effectively already has happened because the wave function must have fully determined

Absolutely not. The wave function describes a "moment" of time and as that function changes time moves forward. All you're saying is "if we have the starting conditions of the universe we can calculate the future conditions". That's called determinism.

Thinking rarely involves predictive modeling.

Do you believe in the law of non-contradiction?

No, all of this is truth statements. You seem to be selective about what true things you consider "truth", so that you can argue against truth while still keeping your own non-truth "true". Subjectivity itself relies on truth, since for something to be subjective it must be true that it is not objective - and so on.

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No, it can also be defined on infinite subsets. That's why I mentioned Cantor sets, because these are measurable uncountable sets, such that choosing an element from it (given uniform choice from the bounded set on which it is defined) has probability 0 (which is different from our finite intuition, that it is impossible).

It is basically just a generalization of the concept of volume.

Logical sure, but not well-founded. We can absolutely arrive at beliefs which logically follow from more fundamental premises that we hold, but to be well founded we would need to demonstrate that those more fundamental premises are themselves true.

I also don't really think we can offer a solid basis for belief. I can explain to you why I believe what I do, and I could go down all the way to the fundamental premises I hold to be true, but the one thing I cannot do is prove to you that those axiomatic assumptions are "more reasonable" than some other set of axiomatic assumptions, especially if your experiences are not compatible with my axiomatic assumptions.

And the clock thing is more highlighting an issue with the article itself; you claim that a common definition of knowledge is "justified true belief", but there is no evidence provided that such a definition is in fact common. Saying you know it's 2:00 after looking at a clock which says 2:00 but is actually not accurate is only an issue if you require knowledge to be justified and true. Since the entire issue is predicated on the definition of the word knowledge, I feel it would be kind of important to establish that problematic definition is both an accepted and common definition, which a quick polling of dictionary.com, Merriam-Webster, and Cambridge would show that they don't really list a definition that if fully compatible with the one you are using. I normally don't like pulling out dictionary definitions in discussions because it feels pedantic in all the wrong ways, but since the entire issue is contingent on the common definition of the word knowledge we need to reasonably establish that the definition being used is the common definition of the word knowledge.

I think the pull of truth is what motivates Norman's introspection: what he ultimately desires is a true belief, not one which is coherent. At each step, he assesses the evidence in light of that goal, and constructs the belief that is the most reasonable approximation he can make of the truth.

Irrespective of knowledge, it feels correct to say that Norman had a reasonable belief the the president was in Florida until he got more evidence. It also makes sense for Norman to characterize his beliefs as reasonable without the need to invoke an outside observer. That belief is grounded in truth as a goal, but ultimately independent of the actual facts in the matter.

Suppose we say that Norman is actually a brain in a vat, and that the president was a figment constructed by alien epistemologists experimenting on his perception. This doesn't and can't change his beliefs since it doesn't alter his evidence: his beliefs are still reasonable since they're the best approximation of truth he's capable of constructing. Norman can never say for sure if any evidence he gets is actually indicative of the truth, but he's still capable of engaging rationally with his evidence in an attempt to seek it out.

The problem is that if we accept the possibility that we're brains in jars, the vast majority of our information becomes unprovable.

Yes, this can occur from believing the answers to unanswerable questions. This isn’t unique to the philosophical brain in a jar scenario, it’s applicable to practically any question that is unanswerable. Basing logic on the answer to an unanswerable question leads to rabbit holes.

I can't disprove the strong skeptical hypothesis, therefore I can't know anything that would be disproven by the strong skeptical hypothesis.

What happens when you try to prove a proposed answer to an unanswerable question? Why try to prove or disprove the “brains in a jar” scenario when it’s unprovable? Do you accept that some questions are unanswerable and that the answers to unanswerable questions are unprovable?

What we know is multi-factorial and begins on a subjective level with sound parameters and practices (like repeatability and other scientific methods) and is confirmed or verified on a shared level. Unprovable scenarios like “brains in jars” can be suggested and can reveal more about unprovables than it does a commonly accepted truth in a commonly accepted shared reality.

I don't think it's an either/or between belief and knowledge. After all, anything I know is also something I believe.

If it is your agenda to say that you believe all that you know then this is just your perspective. I know that I have 5 fingers on my right hand. If you understand and accept the meanings of the words “I have 5 fingers on my right hand”, we occupy the same space in commonly shared reality, and you exist on a human wavelength then upon proving to yourself that I have five fingers on my right hand this information would become knowledge to you without requiring belief. And yes, even then if your agenda is to base all you know on belief then you can do this and I cannot disprove what you believe nor your ability to believe. But then this just says more about you as a person than it does me or commonly shared reality.

What I'm proposing here is that we can have solid justification for holding a belief even in absence of knowledge or proof that the belief is true. On the brain in a jar scenario, I'd say that I can't disprove the hypothesis but that I don't have justification for believing that hypothesis. Between the positions of belief and disbelief, I think that the reasonable position here is disbelief.

People can and do believe whatever they want to, and what people do believe is usually aligned with their bias and agenda.

If I premise other beliefs on this non-knowledge disbelief of strong skepticism, I'd similarly say those beliefs are not knowledge, but nor are they just things that I happen to believe. They're "reasonable beliefs": the most reasonable positions I can take given the evidence I have, even if I don't possess knowledge.

They are unprovable regardless of reasonability.

Thanks for sharing! I really enjoyed reading arguments from a position that differs from my own. Maybe unsurprisingly, I didn’t find them compelling enough to change my view and I’ll briefly touch on why.

One of the central aspects of your argument is scale – ignore the micro-level interactions and just discuss things at the relevant level. And you decide “agents” is the relevant level. As you put it “The little mechanical parts that make up a human body are not the relevant sources of those decisions.”

This ignores the undeniable link between brain chemistry and decision making. Hungry? High cortisol levels in your mother during pregnancy? Just dropped acid? Damage to the VMPFC (…or any part of the brain)? Tired? Chronic overstimulation of dopamine receptors? Stressed? You cannot say that the brain is irrelevant to decisions, as decisions are produced in the brain.

The fact we deliberate is also not evidence of free will. Deliberation is taking into account available options, weighing them against some decision making criteria and selecting a decision. Computer programs do the same thing – we just call it calculations instead of deliberation. The difference is we assume deliberation has some “freedom” somewhere in it, whereas calculations don’t.

But where is that “freedom”? The available options are limited by my external environment and my decision making criteria is based on my brain state at the time and history leading up to that point. Past decisions that impact my current situation or brain state would be met with the same issue. We can following the chain back in time to a point where we obviously have no control (i.e. dictated by external factors or when we hit our “first” decision which would be based on our brain state we had no control over forming – genes, in utero environment, situation we were born into, etc).

We certainly make decision that are our own and unique to us. We have “personal will” but I fail to see where the “free” part enters in. Assuming “the agent” as the level to discuss free will and ignoring the neuroscience (that is responsible for it) just begs the question.

But only if you're still hung up on trying to decide whether or not things are true in the first place. Something being useful doesn't have to be a truth statement. I might find something very useful that you find utterly useless. That is, utility is subjective in a way that truth isn't, which is the best reason for thinking in terms of utility rather than truth. Because most things people believe they believe because they are useful in some way. And recognizing that makes it easierto accept people holding beliefs you personally disagree with. Mostly fighting over whether something is true or not is pointless, especially because when it comes to things like controversial political beliefs, most are rooted in subjective values anyway.

It doesn't avoid the contradiction. Because whether or not something is useful is a truth statement in itself. Without truth usefulness is undefined.

Sure we are omnipotent in this scenario, but I feel there’s ways to put us into the hypothetical. Perhaps later reports come out to show the president actually was in New York. I feel it irksome to say Norman knew the president was in Florida until the evidence pointing to him being in New York out weighed it, when Norman also had that clairvoyant feeling. But I do think the notion of reasonability is getting somewhere, I just still feel the pull of truth being necessary.

Do you think it's possible to state that some of our beliefs are logical and well founded, even in absence of true knowing?

When you state that you "agree to the notion that we can't ever truly know something", that's the crux of why I want to discuss reasonable belief. I agree with that statement, but think we can nonetheless offer a solid basis for belief. If we can't try know things, then using the term "knowledge" for those beliefs feels hollow.

As a less skeptical example, suppose I have a clock that says it's 2:00 PM, but unbeknownst to me my clock stopped fifteen minutes ago and the time is inaccurate. It doesn't make any sense for me to say that I know that it's 2:00, given that it is not in fact 2:00, but I can state that I have a reasonable belief since I don't have any evidence that my belief is inaccurate. Now, I also have a reasonable belief that clocks in general can be wrong; if it's absolutely critical that I know what time it is I should therefore make sure I'm not reliant on that clock as my sole source of information. I can discuss all of this under the umbrella of "reasonable belief" without issue, but can't really do the same from a position of knowledge.

I think most people who reject the notion of "truth" replace it with "utility". That is, rather than insist that X is true or false, they'd evaluate it on whether or not is useful to believe. That avoids the contradiction you mentioned.

The question I would ask is: "Can Norman describe his belief as knowledge?" We can do so in this scenario, but only because of our position as an omniscient outsider. Norman does not have that sort of privileged information.

The relevant question for Norman is what he ought to believe on the basis of the evidence he has. He's got his clairvoyant feelings and some other conflicting external evidence. He can give credence to one or both of those and construct a belief appropriately, which he'll likely do on the basis of other beliefs. In this case, the most reasonable belief in absence of other supporting beliefs (supposing Norman values his clairvoyance) is perhaps a middle position: the President is either in New York or the president is in Florida.

On the other hand, if Norman possesses an evidence-based belief that clairvoyance is impossible, he might dismiss his clairvoyant feelings and conclude that the president is in Florida. Norman would possess a reasonable belief in this case, even if his manifest clairvoyance was in fact accurate. If Norman were to gain additional evidence that the president was in fact in New York (such as a first-hand sighting), he'd be reasonable in revising that belief and in giving more credence to further clairvoyant experiences.

We can categorize Norman's belief as knowledge or non-knowledge in all of these scenarios based on privileged information, but Norman cannot, and Norman's case represents the baseline we should consider when assessing our own beliefs. We can't say if our beliefs amount to knowledge since we aren't omniscient, but we can say if they're reasonable.

> I wrote this more aimed at the skepticism of "you are a brain in a vat" than with criticism of more grounded ideas.

That is all well and good, but I would be hesitant to call such a person a skeptic given that it requires assuming quite a few unverifiable premises. To use the language of your article, I don't believe a Strong Skeptical Hypothesis (SSH) can even exists, because such an argument requires that the one presenting it be inherently lacking in skepticism. A person who posits the idea that "you are a brain in a vat" is either a believer of some form of the simulation hypothesis, or is just being a contrarian for the sake of contrarianism.

For all it's worth, I can agree to the notion that we can't ever truly know something in the sense that we can verify that the information we posses regarding some thing is accurate; I just don't perceive any benefit in using the phrase "reasonable belief" in place of "knowledge".