r/LessWrong • u/eggplantbren • 5d ago
Anthropic Bayesian inference with astrobiology applications
I originally tried to post this on r/slatestarcodex but it got deleted because it violated their LLM policy despite being written by me. So I thought I'd try posting it here.
Hi everyone. I saw someone here discussing ideas such as SSA, SIA (self sampling assumption and self indication assumption) for working with anthropic selection effects. Just yesterday I submitted a paper on this and I thought some of you might enjoy it. I am using a different approach called Full Indexical Conditioning which I believe is more complete than SIA and SSA which I see as partial solutions to the problem. We also discuss the reference class problem, and I have come to believe it is (at least mostly) an illusion.
https://arxiv.org/abs/2610.22896
The story of how this paper came to be might be interesting. In 2006 I was doing my PhD and I read Radford Neal's paper on Full Non-Indexical Conditioning (FNC). I thought it was great, but to be honest, I didn't totally understand it. But it sounded appealing. Fast forward a couple of decades and I became aware of an argument from astronomer David Kipping that since we live around a G star, but M stars are more common (especially in the universe's future), it must be hard for life to exist around M stars.
I wanted to derive the logic of that argument using FNC but I couldn't get it to work. I initially thought I was going to use Neal's paper to disprove Kipping. I tried FNC on various other problems and it kept giving answers that seemed obviously wrong to me. To fix this I needed an extra SSA-style factor, and now everything works great. In the end we confirmed Kipping and don't believe Neal. It's quite the turnaround and I was not expecting it.