Is it better for there to be many people, all of whom have a relatively low quality of life, or for there to be only a few people, all of whom have a relatively high quality of life?
Imagine that you are a government official who must choose between two policies that will bring about drastically different population outcomes. Policy 1 will bring about a population, A, in which there is some number of people, each of whom lives a very high quality of life. Policy 2 will bring about another population, Z, in which there are many more people, each of whom lives a very low but positive quality of life. A and Z are depicted in Figure 1:
Which policy, 1 or 2, should you choose if you want to bring about the better outcome? Most people think you should choose policy 1 because they think the existence of A is better than the existence of Z.
Derek Parfit, however, presents several compelling arguments for the opposite conclusion, that you should choose policy 2 because the existence of Z is better than the existence of A.2 This essay outlines one of those arguments.
1. The Argument
The argument for the conclusion that you should choose policy 2 begins by having us compare two populations, A and A+.
As indicated above, A is made up of some number of people, each of whom lives a very high quality of life. A+ is made up of two groups of people, each of which is the same size as A. Everyone in the first of those groups, like everyone in A, lives a very high quality of life. Everyone in the second of those groups, however, lives a lower quality of life, though a quality of life that’s worth living. A and A+ are depicted in Figure 2:
Which population’s existence would be better, A’s or A+’s? Intuitively, A+’s existence would be better than A’s, for it has additional people whose lives are worth living. Therefore, we should accept:
(P1) A+ is better than A.
Next, we are to compare A+ to a third population, Divided B. Like A+, Divided B is made up of two groups of people, each of which is made up of the same number of people as A. Unlike A+, however, everyone in Divided B lives an equally good life, the quality of which is slightly better than the average quality of life in A+. A+ and Divided B are depicted in Figure 3.
Which population’s existence would be better, A+’s or Divided B’s? Intuitively, Divided B’s is better than A+’s, for although it doesn’t have anyone who is as well off as those in the first group of A+, it has a higher average quality of life than A+, a greater quantity of what makes life worth living than A+, and less inequality than A+. Therefore, we should accept:
(P2) Divided B is better than A+.
Finally, we are to compare Divided B to a fourth population, B. B is identical to Divided B except that it is undivided. Divided B and B are depicted in Figure 4.
Which population’s existence would be better, Divided B’s or B’s? Intuitively, B’s is as good as Divided B’s. Therefore, we should accept:
(P3) B is as good as Divided B.
If B is as good as Divided B, which is better than A+, which is better than A, then B is better than A. Thus, we should conclude:
(C1) B is better than A.
By the same line of reasoning, a fifth population, C, which is made up of twice as many people as B and in which everyone’s quality of life is more than half as good as everyone’s quality of life in B, is better than B (and therefore A). A, B, and C are depicted in Figure 5:
As we move through the alphabet, we arrive at the conclusion that Z is better than Y (and therefore A). Thus, the same line of reasoning that leads us to (C1), that B is better than A, also leads us to the conclusion that Z is better than A and therefore that you should choose policy 2 over policy 1.
2. The Repugnant Conclusion
One might think the lesson of the above argument is that a larger population whose members’ lives are worth living will always be better than a smaller one, but that’s not quite right. Instead, the lesson of the above argument is that a larger population whose members’ lives are worth living will be better than a smaller one provided that the degree to which it is larger is greater than the degree to which the quality of its members’ lives is worse.
We can put the lesson of the above argument more concretely. Parfit, for example, concludes, “For any possible population of at least ten billion people, all with a very high quality of life, there must be some much larger imaginable population whose existence, if other things are equal, would be better even though its members have lives that are barely worth living.”7 He calls this the repugnant conclusion.
The repugnant conclusion gets its name from the fact that it’s hard to accept. Why is it hard to accept? Because although we can imagine a population of ten billion people, each of whom lives a very high quality of life, we cannot imagine another population, made up of people whose lives are barely worth living, being better than the former, no matter how many people there are in the latter.
Given that the repugnant conclusion is hard to accept, many philosophers, including Parfit himself, attempt to resist it by arguing either that the above argument is unsound or that the same line of reasoning cannot get us all the way to the repugnant conclusion.8 Others, however, contend that such arguments are destined to fail.9 If they are correct, then we are forced to accept the repugnant conclusion, however repugnant it may be.
1Arrhenius, Ryberg, and Tännsjö 2014.
2Parfit 1984: 419-441.
3Parfit 1984: 419.
6Parfit 1984: 388.
8Feldman 1995, Hurka 1983, Locke 1987, Narveson 1967, Parfit 1986, Rachels 2001, and Temkin 1987.
9Huemer 2008 and Tännsjö 2002.
Arrhenius, Gustaf, Jesper Ryberg and Torbjörn Tännsjö. “The Repugnant Conclusion.” The Stanford Encyclopedia of Philosophy (Spring 2014 Edition). Ed. Edward N. Zalta. URL = <http://plato.stanford.edu/archives/spr2014/entries/repugnant-conclusion/>.
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About the Author
Jonathan Spelman is an assistant professor of philosophy at Ohio Northern University. He received his PhD in philosophy from the University of Colorado Boulder, and he specializes in normative ethics and metaethics. When he’s not doing philosophy, he enjoys playing golf, taking photos, and spending time with his family. http://jonathanspelman.com