Sean Carroll

In the universe?

Yes, yes, yes.

So sorry, so just to be clear, that's an altered version of the experiment where the coin is flipped after she's awakened on Monday.

Exactly.

Good, a thirder, right.

And the other option is being a halfer.

So the Sleeping Beauty problem is a case of self-locating uncertainty.

But it's a little bit trickier, right?

Rather than just two copies, there's three instances.

There's Heads Monday, Tails Monday, Tails Tuesday.

And the third position will be to assign them equal credences.

I've certainly heard people say exactly those words, but then when they explain why they think it's true, it's very unconvincing.

So I don't know if we're ever going to get there.

So the Sleeping Beauty thought experiment, philosophers love talking about it, but it clearly is closely analogous to things that physicists love talking about, both the anthropic multiverse and the many worlds of quantum mechanics.

So let's try to draw those out more explicitly.

Would you, as a thirder, as someone who gives more credence in the coin landing tales and leading to two awakenings, does that mean if I'm doing the anthropic principle, I should give more credence to universes that have lots of observers in them?

Because I could be any one of those observers.

Let's do it.

I will say as a matter of, I don't know, marketing or whatever you want to call it, the other view for the multiverse or the cosmological theory choice question where you say, I don't give a boost to theories with lots of observers.

I just have a prior.