Imagine these cosmic civilizations of different sizes exist in parallel universes. Then you are more likely to exist in the universe with many humans than with few. This exactly compensates for the effect you describe.
More pictorially: there are two parallel universes (think of them as different planets). In one, Mitchell Porter lives and nobody else. In the other, Mitchell Porter lives along with a billion other people.
But from your perspective, these other people are irrelevant: what you care about is that there are two Mitchell Porters, one in each universe/planet. So you should feel that it’s equally likely that you are in either universe.
The usual way that I dispel the illusion of a ‘reference class’ based on something like sentience (as opposed to something sensible like the class of beings making the same observations as you) is by asking what inferences a nonsentient AI should make, but of course that line of argument won’t convince Mitchell.
Imagine these cosmic civilizations of different sizes exist in parallel universes. Then you are more likely to exist in the universe with many humans than with few. This exactly compensates for the effect you describe.
More pictorially: there are two parallel universes (think of them as different planets). In one, Mitchell Porter lives and nobody else. In the other, Mitchell Porter lives along with a billion other people.
But from your perspective, these other people are irrelevant: what you care about is that there are two Mitchell Porters, one in each universe/planet. So you should feel that it’s equally likely that you are in either universe.
The usual way that I dispel the illusion of a ‘reference class’ based on something like sentience (as opposed to something sensible like the class of beings making the same observations as you) is by asking what inferences a nonsentient AI should make, but of course that line of argument won’t convince Mitchell.