One might also consider condition (iii) of HMV (that is, in worlds where a subject doesn’t exist, we treat her welfare as if it is equal to 0) to be ad hoc. So we treat her as having welfare 0, but only for the purposes of comparing it to her welfare in other worlds. But we don’t actually think she has welfare 0 at that world, because she doesn’t exist. It feels a bit tailor made.
You might think people who exist can compare their own lives to nonexistence (or there are comparisons to be made on their behalf, since they have interests), but an individual who doesn’t exist can’t make any such comparisons (and there are no comparisons to make on their behalf, since they have no interests). From her point of view in the worlds where she exists, she does have welfare 0 in the worlds where she doesn’t exist, but in the worlds where she doesn’t exist, she has not point of view and is not a moral patient.
Or, existing people can have nonexisting counterparts, but nonexisting people do not get counterparts at all, since they’re not moral patients.
You might think people who exist can compare their own lives to nonexistence (or there are comparisons to be made on their behalf, since they have interests), but an individual who doesn’t exist can’t make any such comparisons (and there are no comparisons to make on their behalf, since they have no interests). From her point of view in the worlds where she exists, she does have welfare 0 in the worlds where she doesn’t exist, but in the worlds where she doesn’t exist, she has not point of view and is not a moral patient.
Or, existing people can have nonexisting counterparts, but nonexisting people do not get counterparts at all, since they’re not moral patients.