In general, I think it does matter what you think “actually exists” even outside of what you can observe. For instance, to me it seems like your beliefs about what “actually exists” would affect how you acausally trade, but I haven’t thought about this much.
If I am a Boltzmann brain, and I guess correctly, what do I gain?
If I am not a Boltzmann brain, and I guess incorrectly, what do I lose?
In general, I think it does matter what you think “actually exists” even outside of what you can observe. For instance, to me it seems like your beliefs about what “actually exists” would affect how you acausally trade, but I haven’t thought about this much.