Population Ethics


In my weak ordering post, I brought up a thought experiment that showed that our ethical intuitions often fail at meeting even a the minimal standards of completeness and transitivity.

In particular, if you look at these four universes, it's easy to go round in a circle concerning which is the best:

  1. Alice is very happy; Bob is moderately happy.
  2. Bob is moderately happy.
  3. Bob is very happy.
  4. Bob is very happy; Carol is moderately happy.

Many people are tempted to say that choosing to give birth to someone who is a morally neutral decision - that is, parents shouldn't feel pressured one way or the other to have kids - especially if those kids will be at least moderately happy.

This implies that (1) ~ (2) and that (3) ~ (4). However, it's obvious that making people happy is a good thing, so (3) > (2), which makes (4) > (1). However, (1) and (4) are equivalent in, literally, everything but name.

This should be very troubling.

Population ethics is the study of ethics that affects who ends up existing, and it generally focuses on the ethics of whether and when births/deaths are ethical. The entire field is awash with these kinds of "paradoxes" Population ethics.


Everything we've done up until now has ignored populations, because John Harsanyi only looked at fixed populations Harsanyi, J., C. .

Advocates of utilitarianism typically endorse either total or average utilitarianism. As there names would suggest, total utilitarianism says you should maximize the sum of everyone's utilities, while average utilitarianism says you should maximize the average of everyone's utilities.

These each have significant, but very different issues.

Total Utilitarianism and the Repungnant Conclusion

Total utilitarianism runs into something called the Repugnant Conclusion Mere addition paradox. The argument runs that total utilitarianism implies giving birth is good as long as the person has positive utility - i.e. prefers life to dying. Since the vast majority of people even in very poor countries prefer life to death, this basically implies that we should have huge numbers of children.

A counter argument says that having kids takes away resources from other people, so this wouldn't actually work. But this is generally not regarded as a solid counter, because most people believe that income has strongly diminishing returns.

On the other hand, there are arguments in favor of total utilitarianism. For instance, it seems intuitiavely obvious that if an alien species exist but we will never interact with Earth (e.g. they're outside our light cone), then their existence shouldn't affect what is ethical here on Earth. However, it turns out we can mathematically prove that of all the utilitarian systems, only total satisfies this.

Average Utilitarianism and Eugenics

Average utilitarianism, on the other hand, implies support for eugenics-esque policies. In particular, since happiness is partly genetic Sonja Lyubomirsky, unhappy parents should be prevented from having kids, as their kids would, in expectation, be less happy. Similar arguments can be made for other restrictions on birth.

There is some room for counter-arguments here, in that legally forbidding people from having children forbids people from achieving what, for some, is one of their strongest preferences - this might reduce their utility by enough to outweight the benefits.

However, eugenics is hardly the only problem with average utilitarianism. For instance, imagine a world consisting of one person being tortured, average utilitarianism says we it would be good to create large numbers of people being tortured slightly less - an incredibly unintuitive result!].

Evidence Against Summatarianism?

These are some serious problems with summatarianism. So, why do I still believe?

I said at the beginning, that I was assuming ethics was meaningful, and that I have no way to convince you of this one way or the other. This position means that I only view something as evidence against summatarianism if there is another ethical system that doesn't fall victim to the same problems.

As far as I know, this isn't the case.

You don't need everything we've talked about to prove that a completely intuitive population ethics is impossible. Indeed, many population ethics paradoxes only assume completeness and transitivity, meaning if you want an intuitive population ethics, you either need to reject completeness (and therefore the decision-making ability of your ethical system) or transitivity (and therefore become exploitable).

That's why I don't view these paradoxes as an argument against summatarianism compared to other ethical systems. They demonstrate that our intuitions regarding populations are wildly incoherent, but not that summatarianism is a particularly bad offender.

TODO: Read


Harsanyi, J., C. (1955). Cardinal welfare, individualistic ethics, and interpersonal comparisons of utility. Journal of political economy, 63(4) , 309-321. Mere addition paradox. (2017, October 13). In Wikipedia. Retrieved November 13, 2017, from Population ethics. (2017, October 29). In Wikipedia. Retrieved November 13, 2017, from Sonja Lyubomirsky. (2017, September 2). In Wikipedia. Retrieved November 13, 2017, from Mulgan, T. (2000). Dissolving the mere addition paradox. American Philosophical Quarterly, 37(4), 359-372.