Incommensurability and Vagueness in Population Axiology

Population axiology concerns how to evaluate populations in regard to their goodness, that is, how to order populations by the relations “is better than” and “is as good as.” The main problem in population axiology has been to find an adequate theory about the value of populations where the number of people, the quality of their lives, and their identities may vary. This field has been riddled with impossibility results, which seem to show that our considered beliefs are inconsistent in cases where the number of people and their welfare varies.1 There have been many creative but unfortunately failed suggestions for how to eschew these impossibility results.2 Here I shall consider two suggestions to the effect that incommensurability or vagueness could help.3 We shall start, however, by discussing incommensurability and Derek Parfit’s famous “Repugnant Conclusion.”