Giving one future self u=10 and another u=0 is equally as good as giving one u=5 and another u=5.
So, to give a concrete example, you have $10 dollars. You can choose between gaining 5 utilons today and five tomorrow by spending half of the money today and half of the money tomorrow, or between spending all of it today and gaining 10 utilons today and 0 tomorrow. These outcomes both give you equal numbers of utilons, so they’re equal.
Phil says that the moral reason they’re both equal is because they both have the same amount of average utility distributed across instances of you. He then uses that as a reason that average utilitarianism is correct across different people, since there’s nothing special about you.
However, an equally plausible interpretation is that the reason they are morally equal in the first instance is because the aggregate utilities are the same. Although average utilitarianism and aggregate utilitarianism overlap when N = 1, in many other cases they disagree. Average utilitarianism would rather have one extremely happy person than twenty moderately happy people, for example. This disagreement means that average and aggregate utilitarianism are not the same (as well as the fact that they have different metaethical justifications which are used as support), which means he’s not justified in either his initial privileging of average utilitarianism or his extrapolation of it to large groups of people.
So, to give a concrete example, you have $10 dollars. You can choose between gaining 5 utilons today and five tomorrow by spending half of the money today and half of the money tomorrow, or between spending all of it today and gaining 10 utilons today and 0 tomorrow. These outcomes both give you equal numbers of utilons, so they’re equal.
Phil says that the moral reason they’re both equal is because they both have the same amount of average utility distributed across instances of you. He then uses that as a reason that average utilitarianism is correct across different people, since there’s nothing special about you.
However, an equally plausible interpretation is that the reason they are morally equal in the first instance is because the aggregate utilities are the same. Although average utilitarianism and aggregate utilitarianism overlap when N = 1, in many other cases they disagree. Average utilitarianism would rather have one extremely happy person than twenty moderately happy people, for example. This disagreement means that average and aggregate utilitarianism are not the same (as well as the fact that they have different metaethical justifications which are used as support), which means he’s not justified in either his initial privileging of average utilitarianism or his extrapolation of it to large groups of people.