I’m not sure if I get the idea, so let me ask this:
Suppose there are only two inabitable planets in the whole multiverse—a planet A with 1000 people, and a planet B with 1000000 people. I live in a primitive society, so I don’t have a clue how many people live on my planet. All I know is the information in this paragraph.
Based on the information that “I exist”, should I suppose that I live on a planet A with probability 0.001 and on a planet B with probability 0.999? Or should it be 0.5 and 0.5, because either way, there can be only one me on each planet?
To me it seems that the 0.001 and 0.999 is the correct answer.
Another example: in the whole multiverse there are only four planets. One of them has two inhabitable continents with 1000 people each, two of them have one inhabitable continent with 1000 people and one empty continent, the last one has two empty continents. Seems to me there is 0.5 probability I am one of the 2000 inhabitants of the first planet, and 0.5 probability I am one of the 1000 + 1000 inhabitants of the second and the third planet.
In your examples, you’re using your existence to answer questions about yourself, not about the planets. This is a special case, and not IMHO a very interesting one.
Answering questions about whether there are more or fewer people like you is equivalent to answering which planets exist or what characteristics they have, if those things coincide to some degree. If they don’t, you won’t get much out of anthropic reasoning anyway.
Re-read his examples. He already knows how many planets they are and how many people are on each of them. He’s only trying to figure out which one he’s on.
You do get the idea. Assuming that before taking your existence into account you put .5 probability on each type of planet, then the two options you give are the standard SIA and SSA answers respectively. The former involves treating your existence as more evidence than just that someone exists, as I was suggesting in this post.
I think everyone agrees that in the multiverse case (or any case where everyone exists in the same world) you should reason as you do above. The question is whether to treat cases where the people are in different possible worlds analogously with those where the people are just on different planets or in different rooms for instance.
I’m not sure if I get the idea, so let me ask this:
Suppose there are only two inabitable planets in the whole multiverse—a planet A with 1000 people, and a planet B with 1000000 people. I live in a primitive society, so I don’t have a clue how many people live on my planet. All I know is the information in this paragraph.
Based on the information that “I exist”, should I suppose that I live on a planet A with probability 0.001 and on a planet B with probability 0.999? Or should it be 0.5 and 0.5, because either way, there can be only one me on each planet?
To me it seems that the 0.001 and 0.999 is the correct answer.
Another example: in the whole multiverse there are only four planets. One of them has two inhabitable continents with 1000 people each, two of them have one inhabitable continent with 1000 people and one empty continent, the last one has two empty continents. Seems to me there is 0.5 probability I am one of the 2000 inhabitants of the first planet, and 0.5 probability I am one of the 1000 + 1000 inhabitants of the second and the third planet.
In your examples, you’re using your existence to answer questions about yourself, not about the planets. This is a special case, and not IMHO a very interesting one.
Answering questions about whether there are more or fewer people like you is equivalent to answering which planets exist or what characteristics they have, if those things coincide to some degree. If they don’t, you won’t get much out of anthropic reasoning anyway.
Re-read his examples. He already knows how many planets they are and how many people are on each of them. He’s only trying to figure out which one he’s on.
You do get the idea. Assuming that before taking your existence into account you put .5 probability on each type of planet, then the two options you give are the standard SIA and SSA answers respectively. The former involves treating your existence as more evidence than just that someone exists, as I was suggesting in this post.
I think everyone agrees that in the multiverse case (or any case where everyone exists in the same world) you should reason as you do above. The question is whether to treat cases where the people are in different possible worlds analogously with those where the people are just on different planets or in different rooms for instance.