Suppose we modify the situation so that there is an infinite list of possible Theories of Everything, T1, T2, T3, … With each theory predicting a trillion observers, a trillion trillion observers, a trillion trillion trillion observers, and so on. Additionally, from some other prior info gleaned from scientific insight, the probability of Tn being true is 2^(-n).
SIA here would suggest we live in the universe with the most observers… which in this case doesn’t exist.
Huh! This provides a surprisingly non-zero amount of justification for an intuition I thought was probably just me being stupid—namely my attempt to rescale my utilities as fractions of the total number of observers or integral of observer-moments inside a universe, for purposes of cross-universe comparison.
I don’t think this is a good argument against SIA. The most natural interpretation of SIA gives a posterior of zero for each Ti, so it doesn’t actually say we “live in the universe with the most people”.
“T{i+1} is half a trillion times as likely as Ti” doesn’t actually imply “T{i+1} is more likely than Ti”, because those probabilities are both zero.
Even if we somehow constrained the number of observers to be bounded above by (e.g.) the number of cubed Planck lengths in the universe, our hypothesis under SIA would be… that all such cubes did in fact contain an observer?
Indeed. I just was suggesting that, insofar as we have no evidence of the massive number of observers under SIA, we would have to invent rather unsupported models of the world in order to implement it.
Suppose we modify the situation so that there is an infinite list of possible Theories of Everything, T1, T2, T3, … With each theory predicting a trillion observers, a trillion trillion observers, a trillion trillion trillion observers, and so on. Additionally, from some other prior info gleaned from scientific insight, the probability of Tn being true is 2^(-n).
SIA here would suggest we live in the universe with the most observers… which in this case doesn’t exist.
Huh! This provides a surprisingly non-zero amount of justification for an intuition I thought was probably just me being stupid—namely my attempt to rescale my utilities as fractions of the total number of observers or integral of observer-moments inside a universe, for purposes of cross-universe comparison.
I don’t think this is a good argument against SIA. The most natural interpretation of SIA gives a posterior of zero for each Ti, so it doesn’t actually say we “live in the universe with the most people”.
“T{i+1} is half a trillion times as likely as Ti” doesn’t actually imply “T{i+1} is more likely than Ti”, because those probabilities are both zero.
Even if we somehow constrained the number of observers to be bounded above by (e.g.) the number of cubed Planck lengths in the universe, our hypothesis under SIA would be… that all such cubes did in fact contain an observer?
That’s just a way the universe could turn out to be bigger, not the only way.
Indeed. I just was suggesting that, insofar as we have no evidence of the massive number of observers under SIA, we would have to invent rather unsupported models of the world in order to implement it.