It is unreasonable to think that all simulations are ancestral anyway.
Point taken regarding ancestor simulations, but I don't think that resolves the question. What we choose to do is still evidence about what others will choose to do whether or not the choice is about simulating ancestors or just other possible worlds.
as soon as you can make a complete ancestral simulation ... you can be >99% that you live in a simulation
In Bostrom's formulation there is also the possibility that civilizations capable of ancestor simulations will overwhelmingly choose not to. It's not obvious to me that this is one of the horns of the trilemma to reject.
I can think of at least two reasons why it might be a convergent behavior not to run ancestor simulations:
1) Civilizations capable of running ancestor simulations might overwhelmingly have morals that dissuade them from subjecting sentient beings to such low standards of living as their ancestors had.
2) Such civilizations may wish to exert acausal control over whether they are in a simulation. This is the motivation for my question.
In Bostrom's formulation there is also the possibility that civilizations capable of ancestor simulations will overwhelmingly choose not to. It's not obvious to me that this is one of the horns of the trilemma to reject.
Again, you are making Bostrom's mistake of focusing on ancestral simulations. This is likely why this option seems plausible to you like it did to him - it looks much more plausible that people will decide not to run any ancestral simulations because of their morals than it is that people will decide not to run any simulations whatsoever...
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Of course, for "every Monday", the last one should have been dated July 22-28. *cough*