Ethical Theory Spring 2021

The Repugnant Conclusion


Parfit’s essay raises an important question about how to determine what counts as the best consequences of an action or policy. Specifically, is the best world the one with the most total happiness in it or is it the one with the highest average happiness?

The orthodox utilitarian position is to choose the greatest overall good. Parfit argues that this leads to what he calls the Repugnant Conclusion. It appears that maximizing average utility would be the solution. But Parfit denies that this will work. What he calls the “mere addition paradox” is meant to show that it is better to lower average utility for the sake of increasing the total amount.

That kind of reasoning, of course, leads right back to the Repugnant Conclusion. In the end, Parfit suggests a way of avoiding the Repugnant Conclusion that involves departing from utilitarianism.

For class I am going to make heavy use of a handout rather than these notes. If you can print it out, that will probably work the best as you can take notes in the margins of the handout.

The Mere Addition Paradox

I think the reasoning that leads to the Repugnant Conclusion is clear enough. If you assume that adding more people to the world improves the world, even if it lowers average happiness, you seem to be committed to move from A all the way down to Z.

The reasoning behind the mere addition paradox, by contrast, is not so easy to see. Here the idea is that you add people to the world whose happiness is lower than the average happiness of everyone else. Would anyone say that the world is worse if it moves from A to A+? After all, the only difference is that there are more people in A+ than there were in A and, while their happiness is lower than the average happiness in A, they are all satisfied with life.

If you say “I agree that A+ is at least as good as A,” then Parfit is off to the races. Divided B is better than A+ so Divided B can’t be worse than A. Divided B is the same as plain B. So plain B isn’t worse than A.

So what? Well, we agreed we could stop the slide to the Repugnant Conclusion only if we agreed that plain B is worse than A (and C is worse than B, D is worse than C … Z is worse than Y, so Z is definitely worse than A). And now we have been led by solid-seeming chain of reasoning to the conclusion that plain B is not worse than A. Oops.

Perfectionism as an Answer

Parfit suggests that one way to stop the slide to the Repugnant Conclusion is to adopt a different understanding of what is good and bad. Utilitarianism typically holds that good and bad are measured in terms of happiness and unhappiness (or pleasure and pain). The advantage of that is that it isn’t judgmental. Whatever you like counts. However that generates the problem: everyone will like something and so each possible new life counts for a lot.

Parfit proposes instead that we think of some aspects of human culture as especially valuable: art, say (Parfit 2004, 18–20). If the world is better for having more art in it, then we could have a natural stopping point: the population should not grow so large that there would be no resources for art.

The idea is that we should think that the world is getting better if humanity is being made better or “perfected” (hence “perfectionism”) and that having art is part of becoming better.

One obvious problem with this is that it means leaving behind one of the attractive features of utilitarianism, namely, its non-judgmental, non-elitist theory of what makes things good or bad. But nothing comes for free and maybe it’s worth paying that price.

Maybe “not worse” is not transitive

This is another answer that Parfit considered in a later paper.

Look at these three cases (Parfit 2016, 115):

  1. Being a fairly successful writer is not worse than being a doctor.
  2. Being a doctor is not worse than being a more successful writer.
  3. Being a fairly successful writer is worse than being a more successful writer.

That suggests that “not worse” is not transitive. If it were transitive, then 1 and 2 would logically require that 3 be “being a fairly successful writer is not worse than being a more successful one.”

Why does that matter? Well, the argument leading to the Repugnant Conclusion assumes that “not worse” is transitive. This is from section 6 on the handout (“Back to the Repugnant Conclusion”).

  1. A+ is not worse than A. (established earlier, in point 4 on the handout)
  2. If B is better than A+, then B is not worse than A. (from 7)
  3. B is not worse than A+. (in fact, it’s better; see point 6 on the handout)
  4. Therefore, B is not worse than A. (from 8 and 9)

Key Points

These are the main things you should know from today’s class.

  1. The difference between maximizing total happiness and maximizing average happiness.
  2. The reasoning that leads to the Repugnant Conclusion.
  3. Why the Mere Addition Paradox also leads to the Repugnant Conclusion.


Parfit, Derek. 2004. “Overpopulation and the Quality of Life.” In The Repugnant Conclusion: Essays on Population Ethics, edited by Jesper Ryberg and Torbjorn Tännsjö, 7–22. Dordrecht: Kluwer Academic Publishers.
———. 2016. “Can We Avoid the Repugnant Conclusion?” Theoria 82: 110–27. doi:10.1111/theo.12097.


There was a handout for this class: 09.ParfitRepugnant.handout.pdf