What is the advantage of talking about “this planet” versus standard anthropic SIA as you have used so many times on your blog and elsewhere?
I mean, I can see the disadvantages, those being that it’s really hard to get a good definition of “this planet” that remains constant across universes, especially between universes with different numbers of planets, universes in which you don’t exist, universes in which multiple yous exist, etc.
But with SIA, you can just rephrase it as “I was born on a certain planet, presumably selected randomly among planets in the multiverse that have life, and I call it ‘this planet’ because I was born there.”
(“This is a fertile planet, and we will thrive. We will rule over this planet, and we will call it...This Planet.”)
Now on your diagram, “a planet has life” gives you a 33% chance of being in frames A, B, or C, and “This planet has life” under the previous equivalence with SIA means you choose a randomly selected pink planet and get 50% chance of being in frame A, 25% chance in frame B, and 25% chance in frame C, which justifies your statement that there should be a difference.
This also solves the scientist’s problem just as dspeyer mentions.
I don’t follow why your rephrasing is SIA-specific.
Here I’m not arguing for SIA in particular, just against the position that you should only update when your observations completely exclude a world (i.e. ‘non-indexical’ updating, as in Radford Neal’s ‘full non-indexical conditioning’ for instance). If we just talk about the evidence of existence, before you know anything else about yourself (if that’s possible) SSA also probably says you shouldn’t update, though it does say you should update on other such evidence in the way I’m arguing, so doesn’t have the same problems as this non-indexical position.
I’m addressing this instead of the usual question because I want to settle the debate.
What is the advantage of talking about “this planet” versus standard anthropic SIA as you have used so many times on your blog and elsewhere?
I mean, I can see the disadvantages, those being that it’s really hard to get a good definition of “this planet” that remains constant across universes, especially between universes with different numbers of planets, universes in which you don’t exist, universes in which multiple yous exist, etc.
But with SIA, you can just rephrase it as “I was born on a certain planet, presumably selected randomly among planets in the multiverse that have life, and I call it ‘this planet’ because I was born there.”
(“This is a fertile planet, and we will thrive. We will rule over this planet, and we will call it...This Planet.”)
Now on your diagram, “a planet has life” gives you a 33% chance of being in frames A, B, or C, and “This planet has life” under the previous equivalence with SIA means you choose a randomly selected pink planet and get 50% chance of being in frame A, 25% chance in frame B, and 25% chance in frame C, which justifies your statement that there should be a difference.
This also solves the scientist’s problem just as dspeyer mentions.
I don’t follow why your rephrasing is SIA-specific.
Here I’m not arguing for SIA in particular, just against the position that you should only update when your observations completely exclude a world (i.e. ‘non-indexical’ updating, as in Radford Neal’s ‘full non-indexical conditioning’ for instance). If we just talk about the evidence of existence, before you know anything else about yourself (if that’s possible) SSA also probably says you shouldn’t update, though it does say you should update on other such evidence in the way I’m arguing, so doesn’t have the same problems as this non-indexical position.
I’m addressing this instead of the usual question because I want to settle the debate.