Summary: At a steady state of population, extended lifespan means taking resources away from other potential people. Technology for extended life may not be ethical in this case. Because we are not in steady state, this does not argue against working on life extension technology today.
Many people research radical life extension, dreaming of a day when we might live forever. But I fear that advocates of life extension have overlooked an important concern about immortality: is it ethical?
The argument here is simple, in a world where the population has reached a steady state, another year of life for me reduces the resources available to everyone else. This not only means less resources for existing humans, it also means there would be less resources to support a larger population. In this circumstance, choosing to live another year means preventing someone else from living another year. No one would argue against a 25-year-old choosing to live another year, but what if they are 1000 years old? In steady state population, if they chose to continue for another 1000 years, they are essentially preventing 10 normal human lifetimes within that span. If you were to treat potential or future humans as moral agents in their own right, it might make sense to ask the 1000-year-old to let someone new take their place.
The above argument makes two important assumptions. The most important is that population is in steady state. If population is growing, the above argument becomes much weaker since there are no major resource constraints on creating new life. The second assumption involves taking future generations and potential lives into account. If you don’t care about future people then it doesn’t matter if you are taking resources from them! Similarly, if you do not believe in taking into account your impact on potential human lives, it doesn’t matter that you could give your resources to them.
The first assumption seems like it could be reasonable in the far future (though it may be possible for humanity to continue expanding into space forever). The second assumption is a deep philosophical issue which I will not get into here, but it seems reasonable to me. Taking both of these assumptions as a given, I want to develop some intuition for this problem and suggest some solutions.
At it’s core, immortality is a problem of inequality. In a world of immortals, some people could enjoy centuries of life, while others will never be born due to resource shortages. It seems strange to imagine ghostly people waiting for their chance at life while living people enjoy their extended lifespans. Here is a better counterfactual:
A world with enough resources to be inhabited by 1 person (Bob) who lives for 10,000 years, spending his days engaging in solitary activities such as meditation and blogging.
A world with 100 people (including Bob) each living for 100 years, engaging in group activities such as chess tournaments and Shakespeare-in-the-park (in addition to solitary activities).
Note that these scenarios have the same total life-years and total resources consumed. It is clear that the first scenario involves much higher concentration of life into the hands of one person, whereas the second scenario is more egalitarian.
The second scenario also highlights the fact that with more people, there are more possible activities to do and more opportunities to make friends. This suggests that spreading life-years out more might lead to more overall enjoyment (even for Bob).
Another argument against scenario 1 calls upon on diminishing returns. What happens if Bob runs out of stuff to do after only 1000 years? What would you do for 10,000 years? Each additional year of life will become less and less exciting as you run out of things you haven’t tried. On the other hand, each year of life for a young person is full of wonder, everything is new. Wouldn’t it make sense for an immortal to donate a lifetime to a child? In this framing, scenario 2 looks like a much better deal.
Say we are convinced by the above arguments. What should the immortal citizens of this steady state population do? What laws would encourage people to share life? One simple approach is to allot each person the same number of years of life; after (say) 1000 years of life, a person is required to pass on and make room for someone new. A clever tax scheme could also be used, charging a larger tax for each additional year of life. A complete approach to this problem would require taking into account a persons benefits to society, the strength of their desire to live more, and the benefit of bringing a new person into the world.
This argument does not imply that we should stop trying to extend natural lifespan today, it would be pretty shocking if current the current human lifespan perfectly balanced happiness with equality. Rather, it is important to develop life extension technologies and then think carefully about how to use them. In fact, this might not even become a major issue once such technologies are built. It is possible that many people will choose to pass much sooner than they would be required to. Fortunately, since this future is a long way off, for now this problem is merely interesting to ponder.