Ok. I’ll declare it: I accept David Lewis’ unlimited possible worlds – modal realism [philosophy] as the best and most complete map possible upon which to draw.
Basically, if it could, it did. If it should, it will. Everything possible is true and false and inbetween.
Lewis’ multiverse is *not* the same as Tegmark’s Mathematical Universe but it’s big enough to contain it. Lewis’ multiverse is *not* the same as the multiverse concept in quantum physics but it’s big enough to contain it.
In this philosophical stance, Doctor Who is really traveling through time and space, gliding through possible worlds, changing history in some possible world not so far away from our own universe.
These Universes do not and cannot interact. We can talk about them – we already talk about them.
“What I could have done?” You did.
Was it “you” on this World? No. But you did or rather your counterpart did.
I like this theory, born in 1986 by Lewis because it’s big enough to contain it all.
Now, Lewis has it as a concrete reality. I don’t have to but I can treat it “as if true”.
Why is this useful?
It simplifies possibilities.
Your probability cloud? It stretches across multiple Universes. Simple. Now you can count them if you like.
You have 7 possibilities? You can easily follow each of those 7 possibilities in 7 different worlds. Easy.
Which one is this one? Simple. The actual one. The others have counterparts. They’re you and not you. But you care about them because they’re also you even though you have no contact with them.
Why should you have done [x]?
Because in another universe you did [x].
But that [x] could have ended up in 17 different results that you can imagine.
That’s fine. There are 17 other Universes similar to the Universe in which you did [x] that had 17 other outcomes from there.
It simplifies things. The map is big enough to contain it all without having to feel tied down to this one.
You don’t have to feel bad that your wishes didn’t come true. They did come true.
It clears things up.
You can even inspire yourself by returning to a route you wanted to follow but instead a counterpart you did in another Universe. So, you figure out what that counterpart you did [when you think, “What would I have done if ?”] and you do that here.
It takes the pressure off you here in any case because you on World 0 is not responsible for what World 9823 does but you’re responsible for what you on World 9823 does if you do what World 9823 does here on World 0.
It simplifies truth and lies. It’s all true… somewhere.
We already talk this way. “His facts might be true in his world but not this one that I’m in.” You can treat them both as true and you can measure the distance between his world and your world.
Being Philosophy and not Physics also takes the pressure off.
You can chose to describe physics multiverse effects as belonging only to this Universe or spread it across multiple Universes if you like. There’s room on the map.
I think that’s what I like about it the most: It doesn’t take anything away from anybody. If you want to say “There is only one Universe” you’re also right for as there is no physical interaction between Lewis’ Universes, you’ll only have direct access to one Universe which is this one.
What if this Universe has provable other Universes connected: “leaky” Universes (they leak information)?
In that case, they are STILL properties of *this* Universe – which would then be a Universe with other leaky Universes attached that are unrelated to Lewis’ other Universes because his Universes are not connected in any way.
I’m liking this. It’s big enough to encompass all possibilities without being restricted to mathematics-only (such as Max Tegmark) and it makes it possible to speak about “degrees of truth” or “How close to true” something is by showing how many Worlds away something is from this one.
No matter your results, you’ll still be in this one, even if not-actual ideas belong in another one.