How should we compare a decrease in average quality of life with a gain in population size? Population ethics is a rigorous investigation of the value of populations, where the populations in question contain different (numbers of) individuals at different levels of quality of life. This abstract and theoretical area of philosophy is relevant to a host of important practical decisions that affect future generations, including decisions about climate change policy, healthcare prioritization, energy consumption, and global catastrophic risks.
One of the central questions in population ethics is whether there is a satisfactory way of avoiding the Repugnant Conclusion, according to which:
For any possible population [called A] of at least ten billion people, all with a very high quality of life, there must be some much larger imaginable population [called Z] whose existence, if other things are equal, would be better even though its members have lives that are barely worth living (Parfit 1984).
Most people find the Repugnant Conclusion, i.e. the claim that Z is better than A, to be highly counterintuitive. Thus many take the fact that Total Utilitarianism implies that Z is better than A to count against it, and attempt to find an alternative view in population ethics that avoids this implication. However, as Derek Parfit (Reasons and Persons, 1984) and Gustaf Arrhenius (Population Ethics, forthcoming) have shown, it is difficult to avoid implying the Repugnant Conclusion without taking on board one or more other claims which are, in turn, highly counterintuitive. Many of the puzzles in this area begin by setting up a smooth spectrum of populations, ranging from one in which everyone is at a very high quality of life (as in A) all the way to one in which everyone is at a very low but positive quality of life (as in Z), but where adjacent populations differ only slightly in terms of quality of life.
The views, opinions and positions expressed by these authors and blogs are theirs and do not necessarily represent that of the Bioethics Research Library and Kennedy Institute of Ethics or Georgetown University.