If the multiverse theory is true, then there exists a universe in which it isn't

Nah. Even if we assume that there are infinitely many universes, no two of which are alike, it doesn't follow that you'll be able to find anything at all in particular in one of them.

For example, this is a transcendental number, which implies (among other things) that the decimal representation is infinite and does not repeat, but it doesn't follow that you'll be able to find any particular string in it (for instance, you can't find any string containing a digit other than 1 or 0).

I have another issue with this reasoning, besides the obvious logical fallacy pointed out by cowsarenotevil. I claim the statement is ill-formed because it implies the multiverse theory is somehow a property of any one universe (this is given away by the "in which" phrasing). This is absurd, of course, since the multiverse theory, by definition, makes a statement about the existence of more than one universe. Hence this theory applies not to any one universe, but to the multiverse (the "set of all universes", as it were). All universes refer to the same multiverse theory, they don't have their own (they might have their own perception of said theory, e.g. "there is only one universe I can see", but that is an entirely different theory).

To better understand this, think of a basket of apples. Each apple has a worm on it. A worm on some apple looks around and says, "I see more than one apple". Another worm on another apple also sees more than one apple - of course, they are seeing the same set of apples in the basket. A worm on the opposite side of the basket might not be able to see any apple beyond the one it is on, e.g. because its apple is blocking the view, so it might conclude that there is only one apple. But that doesn't make the theory that "there is only one apple" true, since there are, in fact, multiple apples. This theory is independent of any given worm or apple, as it applies to all apples in the basket. The correct conclusion is that the theory "there are no apples I can see" is true, and that is a property of this particular worm and apple (and that would be a well-formed statement).

This argument can be made rigorous using type theory, or, I suppose, any remotely consistent logic system, but it's not hard to see that the statement is meaningless if you think about it this way. The paradox essentially plays on the unconditional nature of the multiverse theory versus each universe's interpretation of it. It you separate the two properly, the paradox disappears (and the statement becomes uninteresting).

the statement is ill-formed because it implies the multiverse theory is somehow a property of any one universe (this is given away by the "in which" phrasing).

Yup.

the statement is ill-formed because it implies the multiverse theory is somehow a property of any one universe (this is given away by the "in which" phrasing).

Well, no... we are a property of one universe, and all we can see and understand is very limited aspects of a very small part of one universe.

Who said that whatever the multiverse is part of has to make sense (in your opinion) or has to follow your rules of logic? It might be possible that an universe is part of the multiverse but within that universe's scope, no such thing as a multiverse exists. Or, it might be possible that one of an infinite number of multiverses (with an infinite number of universes each) exists and each multiverse does not exist at the same time. Maybe it even only exists as long as you don't look at it from the outside, or as long as 50.01% of the sentient beings inside it believe so. Who could tell without having visited another universe at the very least. Anything anyone says is just talk.

It's not like physics in our single-universe are always consistent and well-understood and don't have strange quirks. Practically all of quantum physics is "ill-formed" if you look at it from a "normal" angle, but it nevertheless verifiably and reproducably works (or at least seems to work) that way.

Why can't something that is much bigger than an universe have even bigger quirks? Why does it have to follow your logic?

"It might be possible that an universe is part of the multiverse but within that universe's scope, no such thing as a multiverse exists."

But if you can change things around like that, I might as well say: "but in our Universe, the multiverse exists, even within that Universe's scope".

If a property like "existence" can change around like that, you had better define what we really mean by that term.

"Practically all of quantum physics is "ill-formed" if you look at it from a "normal" angle, but it nevertheless verifiably and reproducably works (or at least seems to work) that way."

Quantum physics may seem unintuitive, and different to what people normally observe, but quantum mechanics is a mathematically consistent system. I suppose yes, you could say there are things like "a cat being both alive and dead at the same time", but this is all built on a logical mathematical system. But if people just say things like existing and not existing at the same time, without the definitions or maths to explain it, it's meaningless.

"a cat being both alive and dead at the same time"

That one is a particularly bad example though, since in reality the cat couldn't care less whether you know that it's dead or not. The kill mechanism going off and you looking are unrelated things, and the latter doesn't change the cat's state in retrospective, nor is the cat in a fluent state before. Unknown, yes. Unknown to you. But the cat doesn't care whether you know (nor does the kill mechanism).

Flash memory would be a better example. The electrons obviously cannot cross the isolative layer to make it into the charge trap, yet they demonstrably do. They do so without crossing it, which is, of course, entirely impossible. Yet, they do. Everybody who is using a flash drive proves it every day.

It doesn't really matter much what mathematical concept people have built around it to explain it. The concepts may look sound, but the theories of Socrates and Aristotle looked sound, too, at some time. What matters is that nature gives a fuck about what we think is right.

My point is, the fact that it doesn't seem to make sense to you or doesn't fit your equations doesn't mean that it is necessarily wrong or impossible. It might as well be that you simply can't see far enough. Much as in the above worm-in-apple allegory. Except compared to the universe, we're more like bacteria living on a worm's butt in an apple in a basket loaded on a huge truck, and trying to tell what's going on in a different city, based on tales that another bacterium who never got out of that same apple told us.

Who said that whatever the multiverse is part of has to make sense (in your opinion) or has to follow your rules of logic? It might be possible that an universe is part of the multiverse but within that universe's scope, no such thing as a multiverse exists.

No, that makes no sense; you are saying "is it not possible for an apple to be in a basket but at the same time for the basket not to exist" - you can't have one or the other. If something is part of the multiverse then from inside the universe the multiverse must exist. Now, as to if any intelligent life inside that universe has hit upon the theory is another matter.

However a multiverse is made up of a set of universes (defined as enclosed regions of space-time) therefore if a universe exists it is in a multiverse.

As to if multiverses exist, that is also another matter (set of universes which have their own distinct boundary conditions).

There is also nothing, afaik, which states there must be an infinite number of universes; for all we know there could be 57 of them. Or maybe there was 2000 and over time they ceased to exist for various reasons. Maybe there is an infinite number but this is the only one where the correct Laws Of Physics played out to allow for life to questions these things.

However, as far as the human definition of a universe and multiverse goes there is no way for one to exist outside the other or indeed for a universe to prevent a multiverse from existing. Trying to say otherwise is like saying that when you cover your eyes the universe no longer exists because you can't see it.

Multiverse my ###! It's pure sci-fi!

I'll bet my left kidney that there is precisely one infinite universe. The expansion after the 'big bang' is simply a proper of our particular region of the universe.

NB: I could be wrong!

Who said that whatever the multiverse is part of has to make sense (in your opinion) or has to follow your rules of logic? It might be possible that an universe is part of the multiverse but within that universe's scope, no such thing as a multiverse exists.

No, that makes no sense; you are saying "is it not possible for an apple to be in a basket but at the same time for the basket not to exist" - you can't have one or the other. If something is part of the multiverse then from inside the universe the multiverse must exist.

I was hoping that part of the post was a joke, but that is correct.

Multiverse means a collection of more than one. It is either part of the collection or not. The original post was nonsensical, illogically claiming if you have something in a group it can also be not part of the same group.

There is also nothing, afaik, which states there must be an infinite number of universes; for all we know there could be 57 of them. Or maybe there was 2000 and over time they ceased to exist for various reasons. Maybe there is an infinite number but this is the only one where the correct Laws Of Physics played out to allow for life to questions these things.

In most existential reasoning the numbers are "zero", "exactly one", and "unbounded more than one". Under the multiverse theories there is an unbounded number of them. The cool thing about unbounded numbers is that they can be any number, including 57 and 2000.


I do tend to agree. If one, why not more than one? That does not necessarily mean an uncountably infinite number of them, but the numbers are 0, 1, >1, with 1 being a rare condition.