Mere addition paradox
From Wikipedia, the free encyclopedia
The mere addition paradox is a problem in ethics, identified by Derek Parfit, and appearing in his book, Reasons and Persons. The paradox identifies apparent inconsistency between three seemingly true beliefs about population ethics.
Contents |
[edit] The paradox
The paradox arises from consideration of three different possibilities. The following diagrams show different populations, with population size represented by column width, and the population's happiness represented by column height. Note that for each group of people represented, everyone in the group has exactly the same level of happiness.
 |
 |
 |
| A | A+ | B |
|---|
In population A, everyone is very happy.
Population A+ consists of 2 groups - the same group as in A, and another population which is less happy, but whose lives are nevertheless worth living. The two populations are entirely separate, that is, they cannot communicate and are not even aware of each other. As this is a mere addition of people with lives worth living, it seems that, all things considered:
1) A+ is not worse than A.
Population B is the same size as population A+, and its average happiness is higher than A+, though slightly lower than A. Since A+ and B have the same number of people and because there is a greater level of equality and average happiness in B, it seems that, all things considered:
2) B is better than A+.
Finally, Parfit argues that, all things considered:
3) B is worse than A.
The argument for (3) is as follows: If B is better than A, then seemingly a larger population, C, standing in the same relation to B as B does to A, would be better still. Population D, twice as large and with a somewhat lower level of happiness would then be better than C, and so on, until reaching the Repugnant Conclusion that the best outcome is Z, an enormous population with all members having lives barely worth living. Claim (3) follows if we reject the Repugnant Conclusion and hold that Z is worse than A.
A paradox results. (1), (2), and (3) each seem true. However, it seems that all three claims cannot be true. For instance, (1) and (2) imply that B is not worse than A. But this conflicts with (3), which states that B is worse than A.
 |
| Z |
|---|
[edit] Objections and resolutions of the paradox
Some argue that the paradox can be defeated by denying claim (1), that adding people of less-than-average happiness into the world does not make the overall situation worse. Claim (1) is not universally accepted; for example one branch of utilitarianism aims at maximizing average happiness. However, rejecting claim (1) commits one to the position that it is actually bad for people of less-than-average happiness to be born, even if their lives are worth living. A more sophisticated rejection of claim (1) might argue for some threshold above the level at which lives become worth living but below which additional lives would nonetheless make the situation worse. Parfit argues that for this position to be plausible, such a threshold would be so low as to apply only to lives that are "gravely deficient" and which, "though worth living ... must be crimped and mean." Parfit calls this hypothetical threshold the "bad level," and argues that its existence would not resolve the paradox because population A would still be better than an enormous population with all members having lives at the "bad level."
Alternatively, one could attempt to resolve the paradox by rejecting claim (2), that B is better than A+. However, rejecting claim (2) implies that what is most important is the happiness of the happiest people, and commits one to the view that a small increase in the happiness of the happiest people outweighs a (bigger) decrease in the happiness of less happy people.
Some have taken the approach of denying the paradox altogether by arguing for the intransitivity of the "better than" relation.
