A simplification: SIA + individual impact = SSA + total impact
ie if I think that worlds with more copies are more likely (but these are independent of me), this gives the same behaviour that if I believe my decision affects those of my copies (but worlds with many copies are no more likely).
A simplification: SIA + individual impact = SSA + total impact
ie if I think that worlds with more copies are more likely (but these are independent of me), this gives the same behaviour that if I believe my decision affects those of my copies (but worlds with many copies are no more likely).