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Overpopulation and the Quality of LifeEdit

Parfit's article[1], which describes the repugnant conclusion, begins by asking whether it is possible for there to be overpopulation - too many people living. If population increases, quality of life can be lost. There are two competing utilitarian approaches to population:

  • Averaging: "It is better if, on average, people's lives go better"
  • Totalling: "it is good if any extra life is lived, that is worth living"
File:Repugnant conclusion.jpg

The repugnant conclusionEdit

Parfit's repugnant conclusion, shown in Figure 2, is a famous challenge to total utilitarianism. Here, B is better than A. C is better than B. Z is best of all. In Z, an "an enormous population all of whom have lives not much above the level where they would cease to be worth living". In Z, there is the greatest quantity of whatever makes life worth living, thus it is favoured by the total utilitarian. In Parfit's words: "Compared with the existence of very many people-say, ten billion-all of whom have a very high quality of life, there must be some much larger number of people whose existence, if other things are equal, would be better, even though these people would have lives that are barely worth living". This total utilitarian conclusion seems terrible.

Parfit's compares his challenge to utilitarianism to Nozick's utility monster argument: "[The utility monster] is someone who would gain more happiness than we would lose whenever he is given any of our resources…How could it be true that, if all mankind's resources were given to Nozick's Monster, this would produce the greatest total sum of happiness? For this to be true, this Monster's life must, compared with other people's lives, be millions of times as much worth living. We cannot imagine, even in the dimmest way, what such a life would be like. Nozick's appeal to his Monster is therefore not a good objection to the Total Principle. We cannot test a moral principle by applying it to a case which we cannot even imagine." Parfit argues that Z, on the other hand, can be imagined: "We can imagine what it would be for someone's life to be barely worth living-containing only muzak and potatoes. And we can imagine what it would be for there to be many people with such lives. In order to imagine Z, we merely have to imagine that there would he very many."

The mere addition paradoxEdit

File:Mere addition paradox.jpg

Parfit's next example brings our intuitions in conflict with each other. There are four scenarios:

  • A: a large and relatively happy population
  • B: a somewhat less happy population that is twice as large
  • A+: a world with not just A but also another less happy population of equal size. The inequality in A+ is natural, not caused by societal injustice. On average, A+ is less happy than B.
  • Divided B: there is a population where all individuals have he same happiness as in B but they are divided as per A+.

Parfit compares these intuitively:

  1. B is worse than A because the average quality of life is worse. This is the first arm of his paradox.

His opposite line of reasoning is more complex:

  1. Divided B is better than A+, using any form of utilitarianism or egalitarianism.
  2. Divided B is equal to B.
  3. A+ is not worse than A. Just because there is inequality in A+, does not suggest that the extra group should never have existed. "Why are they such a blot on the universe?"
  4. From 2, 3 and 4, B is not worse than A. (B is equal to divided B, which is better than A+, which is not worse than A)

So our intuitions lead us to believe both that B is both worse and not worse than A. Parfit does not argue for any particular solution to the paradox.

The second paradoxEdit

In Parfit's next example, there are two possible future worlds, A+ and Alpha. Parfit considers two arguments that A+ is better than Alpha:

  • The worst-off individuals in Alpha are worse off than the worst-off individuals in A+
  • The worst-off individuals in A+ are better off than the worst-off individuals in Alpha. This is the Rawlsian view. Parfit criticises it fiercely. In the Rawlsian view, he says, whichever people are worst-off ought not exist. Then, they will be replaced by the second worst. The calculation is then repeated until only the best-off people remain. To Parfit, this is absurd.
File:The second paradox.jpg

On the other hand, Parfit recognises two arguments that Alpha is better than A+:

  • Taking the two first columns in A+ to correspond to the first two columns in Alpha, the individuals who exist in A+ are made happier in Alpha (A prior-existence approach)
  • The ratio of worse-off to best-off individuals is larger in Alpha. The idea is that if this ratio is extremely large, then there are so few better-off individuals that the inequality loses its importance.

On balance, Parfit regards Alpha as superior to A+. The next step is from Alpha to Beta. This is slightly different because it makes the situation worse for those best off. However, it is attractive to Parfit because it reduces inequality. The step from Beta to Gamma is the same as the step from Alpha to Beta. So it continues until Omega, which must be the best situation of all so far. These steps are repeated, leading us through Alpha 2, Beat 2, Gamma 2, and Omega 2. So it continues until Omega 100, which must be superior to A+. However, the people in Omega 100 have lives barely worth living at all so we have once again arrived at the repugnant conclusion.

The drab eternityEdit

Parfit takes the repugnant conclusion and applies it to a single person's life. Then, a hundred years of ecstasy is compared to the "Drab Eternity". Parfit favours the former, even though the latter includes an infinity of days worth living.

Parfit begins to make room for a solution to the repugnant conclusion: must a life barely worth living consist of just musak and potatoes? It seems like in this life, all of the best things in life - "creative activity", "aesthetic experience", "relationships" - are gone. Instead, suppose that the best things in life are still present, but are just more sparse. Then, Z and Omega 100 become less repugnant.

To the second paradox, Parfit gives the following answer: "What we might appeal to is not elitism, but Perfectionism. In the move from Alpha to Omega 100, the best things if life must have disappeared. Suppose for instance that, in the move from Alpha to Beta, Mozart's music would be lost, in the move to Gamma, Haydn's. In the move to Delta, Venice would be destroyed, in the move to Epsilon, Verona." Parfit says that if we are to be compelled to perfectionism, we must arrest the move from Alpha to Omega in one of the first steps. To stop the process towards the end, when all that is left to be salvaged is "a bad performance of Ravel's Bolero" would be silly. The problem with perfectionism, which Parfit identifies, is that although Mozart is nothing like musak, a smooth continuum can be made between the two. So, although Parfit is not fully satisfied with perfectionism, it is his best effort to avoid the repugnant conclusion.

Huemer's Support of the Repugnant ConclusionEdit

Michael Huemer argued in favor of the repugnant conclusion[2]. Part of his argument was a thought experiment that compared three worlds.

  • World A is home to 1 million happy people with welfare level 100.
  • World A+ is home to those same people but with welfare level 101 and home to 99 million new people with welfare level 1 (where 1 means barely worth living).
  • World Z is home to the same 100 million from World A+ but at welfare level 3.

Total utility in each world is 100, 200, and 300 respectively.

Huemer reviewed the premises of the problem and concluded that they are true, but then addressed why people dislike the conclusion. He described five conditions under which people might have a basis for adhering to a conclusion despite an argument against it. His example was of a person who knows that motion exists but is unable to resolve Zeno's paradox.

One of Huemer's arguments was that people imagine themselves in world A with high utility and focus on the drop in utility associated with the move to world A+ but they fail to consider the large number of people who have the opportunity to live lives in A+. Another argument is that people might fail to comprehend the large numbers. Another argument was related to the failure to comprehend compounding of small numbers. One example was that people do not want to reduce the speed limit to save lives because of the large number of small inconveniences that would arise from the change (although this example seems to indicate that people can add the small inconveniences and perceive great value in it). Another argument is that people underrate low-quality lives by imagining them to be worse that the intended state.

Huemer identified six arguments that attack the repugnant conclusion and dismissed each one. An emphasis on average utility only would imply the sadistic conclusion in which it would be better to attain a lower total utility by adding one person with extremely negative utility than by adding many people with low, but positive utility. Huemer also opposes Parfit's idea of Perfectionism because of an unintended implication: "Perfectionism implies that enabling a few people to hear Mozart’s music might be more important than providing food, shelter, and medical care to millions." (Huemer, p. 914).

In addition to Huemer's comments, part of the repugnance of the conclusion is that we assume that the forces that lead to the highly-populated world will continue to cause increased population thereby continuing growth until total average utility drops low enough to decrease total utility.


  1. Derek Parfit, "Overpopulation and the Quality of Life." published, among other places, in Jonathan Glover's Utilitarianism and its Critics
  2. Huemer, M. (2008). In defence of repugnance. Mind, 117(468). DOI: 10.1093/mind/fzn079

Further ReadingEdit