According to Parfit’s premises, the bestest imaginable world is one with an enormous number of extremely happy people. This world isn’t physically possible though due to resource constraints.
The mere addition thing shows that in general we are indifferent between small numbers of happy people and large numbers of unhappy people (actually the argument just shows “no worse than”—you’d need to run a similar argument in the other direction to show you’re actually indifferent).
Now consider the (presumably finite?) space of all worlds that are possible given resource constraints. Pick the world W0 with the highest utility, U0.
Now think about the U0 indifference curve. Where does W0 lie along this curve? It is surely whichever world is cheapest—the only world along this curve that fits within our budget (actually there may be multiple points that come exactly on budget, but there won’t be any that come below budget because then we’d be able to up the happiness/population a bit and achieve some greater utility U1).
if the cheapest world on our indifference curve happens to be the one with an enormous amount of very unhappy people, then we’d reach a repugnant conclusion. But given our original assumptions that’s not necessarily so.
Can I try my own summary?
According to Parfit’s premises, the bestest imaginable world is one with an enormous number of extremely happy people. This world isn’t physically possible though due to resource constraints.
The mere addition thing shows that in general we are indifferent between small numbers of happy people and large numbers of unhappy people (actually the argument just shows “no worse than”—you’d need to run a similar argument in the other direction to show you’re actually indifferent).
Now consider the (presumably finite?) space of all worlds that are possible given resource constraints. Pick the world W0 with the highest utility, U0.
Now think about the U0 indifference curve. Where does W0 lie along this curve? It is surely whichever world is cheapest—the only world along this curve that fits within our budget (actually there may be multiple points that come exactly on budget, but there won’t be any that come below budget because then we’d be able to up the happiness/population a bit and achieve some greater utility U1).
if the cheapest world on our indifference curve happens to be the one with an enormous amount of very unhappy people, then we’d reach a repugnant conclusion. But given our original assumptions that’s not necessarily so.