Mere addition paradox
The Mere Addition Paradox is a problem in utilitarian ethics, due to Derek Parfit, and first appearing in his book, Reasons and Persons.
The paradox appears to show that it is better to have a large population, where everyone has a life that is just barely worth living, than a small population where everyone is very happy.
The paradox arises from consideration of 3 different possibilities. The following diagrams show different populations, with population size on the x-axis, and the happiness of each individual on the y-axis.
| File:Mere Addition A.png | File:Mere Addition A Plus.png | File:Mere Addition B.png |
| A | A Plus | B |
|---|---|---|
In population A, everyone is very happy.
In population A Plus, the same group as in A has had added to it a group that is moderately happy. As this is a mere addition of reasonably happy people, Parfit argues that it is no worse than the state of affairs in A.
Population B is the same size as population A Plus, but the average happiness is higher than A Plus, though slightly lower than in A. Since the average happiness is higher than in A Plus, Parfit argues that the state of affairs in B is no worse than that of A Plus, and therefore, no worse than that of A.
The paradox comes because this argument is repeatable until we reach something like Z, a huge population of people whose lives are only just worth living (on these graphs, negative values would indicate lives not worth living).
| File:Mere Addition Z.png |
| Z |
|---|
Thus, the state of affairs in Z is no worse than the state of affairs in A. Parfit calls this the Repugnant Conclusion, and rejects it, but says he does not have a solution.