Has anyone here ever addressed the question of why we should prefer
(1) Life Extension: Extend the life of an existing person 100 years
to
(2) Replacement: Create a new person who will live for 100 years?
I've seen some discussion of how the utility of potential people fits into a utilitarian calculus. Eliezer has raised the Repugnant Conclusion, in which 1,000,000 people who each have 1 util is preferable to 1,000 people who each have 100 utils. He rejected it, he said, because he's an average utilitarian.
Fine. But in my thought experiment, average utility remains unchanged. So an average utilitarian should be indifferent between Life Extension and Replacement, right? Or is the harm done by depriving an existing person of life greater in magnitude than the benefit of creating a new life of equivalent utility? If so, why?
Or is the transhumanist indifferent between Life Extension and Replacement, but feels that his efforts towards radical life extension have a much greater expected value than trying to increase the birth rate?
(EDITED to make the thought experiment cleaner. Originally the options were: (1) Life Extension: Extend the life of an existing person for 800 years, and (2) Replacement: Create 10 new people who will each live for 80 years. But that version didn't maintain equal average utility.)
*Optional addendum: Gustaf Arrhenius is a philosopher who has written a lot about this subject; I found him via this comment by utilitymonster. Here's his 2008 paper, "Life Extension versus Replacement," which explores an amendment to utilitarianism that would allow us to prefer Life Extension. Essentially, we begin by comparing potential outcomes according to overall utility, as usual, but we then penalize outcomes if they make any existing people worse off.
So even though the overall utility of Life Extension is the same as Replacement, the latter is worse, because the existing person is worse off than he would have been in Life Extension. By contrast, the potential new person is not worse off in Life Extension, because in that scenario he doesn't exist, and non-existent people can't be harmed. Arrhenius goes through a whole list of problems with this moral theory, however, and by the end of the paper we aren't left with anything workable that would prioritize Life Extension over Replacement.
I don't see how this is a paradox at all.
Scenario (1) creates 100 years of utility, minus the death of one person. Scenario (2) creates 100 years of utility, plus the birth of one person, minus the death of two people. We can set them equal to each other and solve for the variables, you should prefer scenario (1) to scenario (2) iff the negative utility caused by a death is greater than the utility caused by a birth. Imagine that a child was born, and then immediately died ten minutes later. Is this a net positive or negative utility? I vote negative and I think most people agree; death outweighs birth.
(As an interesting sidenote, if we lived in a world where the value of Birth outweighed the value of Death, I think most of us would happily change our preference ordering. Eg, If we lived in the Children of Men world, we'd go with scenario (2) because a new birth is more important than a new death. Or if we lived in a universe where there really was a heaven, we'd go with scenario (2) as well because the value of death would be near zero.)
Things get less simple when we take into account the fact that all years and deaths don't generate equal (dis)utility. The disutility caused by Death(newborn) != Death(10 year old) != Death (20 year old) != Death (80 year old) != Death (200 year old). Similarly, the utility generated by a child's 3rd->4th year is nowhere near equivalent to the utility of someone's 18th->19th year. I would assume the external utility generated by someone 101st->200th year to far, far outweigh the external utility generated by the 1st->100th year (contributing to the world by being a valuable source of wisdom). By any reasonable calculations it seems that net utility in scenario (1) significantly outweighs the net utility of scenario (2).
Different people might have different expected values for the utility and disutility of years/deaths, and thus get differing results. But it seems if you had sufficiently accurate data with which to calculate expected utility, you could actually determine what those utilities are and they wouldn't come out equal. However, just because something is incredibly hard to calculate doesn't mean you throw your hands up and say that they must be equal. You do what you always do with insufficient information: approximate as best you can, double check your numbers, and hope you don't miss anything.
I'm not sure about the Children of Men example: a birth in that situation is only important in that it implies MORE possible births. If it doesn't, I still say that a death outweighs a birth.
But here's another extremely inconvenient possible world:
People aren't 'born' in the normal sense - instead they are 'fluctuated' into existence as full-grown adults. Instead of normal 'death', people simply dissolve painlessly after a given amount of time. Nobody is aware that at some point in the future they will 'die', and whenever someone does all currently existing people have their memories instantly modified to remove any trace of them.
I still prefer option (1) in this scenario, but I'm much less confident of it.