The self-indication assumption seems to violate some pretty basic probability. Suppose that there are two possible universes: universe A has one person, and universe B has 99 people. Suppose that the prior probability for each is 50%. Under SIA, you are 1% likely to be each one of these 100 possible people. But that means that universe B has 99% probability, even though we just assigned it 50% probability. It can't change without updating on evidence, which we never did. What happened?

We updated on the fact that we exist. SSA does this a little too: specifically, the fact that you exist means that there is at least one observer. One way to look at it is that there is initially a constant number of souls that get used to fill in the observers of a universe. In this formulation, SIA is the result of the normal Bayesian update on the fact that soul-you woke up in a body.

Open thread, Dec. 15 - Dec. 21, 2014

by Gondolinian 1 min read15th Dec 2014309 comments


If it's worth saying, but not worth its own post (even in Discussion), then it goes here.

Previous Open Thread

Next Open Thread

Notes for future OT posters:

1. Please add the 'open_thread' tag.

2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)

3. Open Threads should be posted in Discussion, and not Main.

4. Open Threads should start on Monday, and end on Sunday.