Population ethics concerns how to evaluate future populations regarding their goodness or choiceworthiness all things considered, or in terms of “socially preferred” to use a terminology more familiar in social choice theory and welfare economics. The field has been riddled with paradoxes and impossibility theorems which seem to show that people’s considered judgments are inconsistent in this area. This chapter considers what the impossibility theorems mean for the project of normative ethics and moral justification. It starts by presenting the impossibility result that involves the logically weakest and intuitively most compelling conditions and then discusses a few proposed but failed ways to avoid the theorem. Finally, the chapter turns to the implications of the impossibility theorem for moral justification and the project of normative ethics, including a novel argument for non-cognitivism and a new type of debunking argument.

Population axiology concerns how to rank populations by the relation “is socially preferred to”. So far, population ethicists have (with important exceptions) focused less on the question of how to rank population prospects, that is, alternatives that contain uncertainty as to which population they will bring about. Most public policy choices, however, are decisions under uncertainty, including policy choices that affect the size of a population (such as climate policy choices). Here, we shall address the question of how to rank population prospects by the relation “is socially preferred to”. We start by illustrating how well-known population axiologies can be extended to population prospect axiologies. And we show that new problems arise when extending population axiologies to prospects. In particular, traditional population axiologies lead to prospect-versions of the problems that they are praised for avoiding in the risk-free settings. Moreover, we show how the axiom of State-Wise Dominance allow us to extend any impossibility theorem in population axiology to impossibility theorems for non-trivial population prospects, that is, prospects that confer probabilities strictly between zero and one on different populations. Finally, we formulate impossibility results that only involve probabilistic axioms. 

There are two classic principles for deciding who should have a right to vote on the laws, the All Affected Principle and the All Subjected Principle. This article is devoted, firstly, to providing a sympathetic reconstruction of the All Subjected Principle, identifying the most credible account of what it is to be subject to the law. Secondly, it shows that that best account still suffers some serious difficulties, which might best be resolved by treating the All Subjected Principle as a subset of the All Affected Principle with which the All Subjected Principle must in any case be supplemented.

Parfit (Theoria 82:110–127, 2016) responded to the Sequence Argument for the Repugnant Conclusion by introducing imprecise equality. However, Parfit’s notion of imprecise equality lacked structure. Hájek and Rabinowicz (2022) improved on Parfit’s proposal in this regard, by introducing a notion of degrees of incommensurability. Although Hájek and Rabinowicz’s proposal is a step forward, and may help solve many paradoxes, it can only avoid the Repugnant Conclusion at great cost. First, there is a sequential argument for the Repugnant Conclusion that uses weaker and intuitively more compelling assumptions than the Sequence Argument, and which Hájek and Rabinowicz’s proposal only undermines, in a principled way, by allowing for implausible weight to be put on the disvalue of inequality. Second, if Hájek and Rabinowicz do put such implausible weight on the disvalue of inequality, then they will have to accept that a population A is not worse than another same sized population B even though everyone in B is better off than anyone in A.

This chapter sets out the main normative dimensions that should be used in assessing whether societies have made social progress and whether a given set of proposals is likely to bring progress. Some of these dimensions are values, bearing in the first instance on the evaluation of states of affairs; others are action-guiding principles. Values can inspire and in that sense also guide actions. Principles aim to offer more specific guidance on how to rank, distribute, and realize values. Recognizing a multiplicity of values and principles is important not only to being respectful of the variety of reasonable views about what matters but also because it is difficult to reduce the list of dimensions that ultimately matter to a shorter one in a way that reflects all aspects of the phenomena in question. Many of the chapters that follow will explicitly address only a subset of these values and principles: the ones most salient for their issues or areas; but in principle, all remain relevant.

Who should have a right to take part in which decisions in democratic decision making? This “boundary problem” is a central issue for democracy and is of both practical and theoretical import. If nothing else, all different notions of democracy have one thing in common: a reference to a community of individuals, “a people”, who takes decision in a democratic fashion. However, that a decision is made with a democratic decision method by a certain group of people doesn’t suffice for making the decision democratic or satisfactory from a democratic perspective. The group also has to be the right one. But what makes a group the right one? The criteria by which to identify the members of the people entitled to participate in collective decisions have been surprisingly difficult to pin down. In this paper, I shall revisit some of the problems discussed in my 2005 paper in light of some recent criticism and discussion of my position in the literature, and address a number of new issues.

In Derek Parfit’s original formulation the Repugnant Conclusion is stated as follows: “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” (Parfit 1984). The Repugnant Conclusion highlights a problem in an area of ethics which has become known as population ethics. The last three decades have witnessed an increasing philosophical interest in questions such as “Is it possible to make the world a better place by creating additional happy people?” and “Is there a moral obligation to have children?” The main problem has been to find an adequate theory about the moral value of states of affairs where the number of people, the quality of their lives (or their life-time welfare or well-being - we shall use these terms interchangeably here), and their identities may vary. Since, arguably, any reasonable moral theory has to take these aspects of possible states of affairs into account when determining the normative status of actions, the study of population ethics is of general import for moral theory. As the name indicates, Parfit finds the Repugnant Conclusion unacceptable and many philosophers agree. However, it has been surprisingly difficult to find a theory that avoids the Repugnant Conclusion without implying other equally counterintuitive conclusions. Thus, the question as to how the Repugnant Conclusion should be dealt with and, more generally, what it shows about the nature of ethics has turned the conclusion into one of the cardinal challenges of modern ethics.

Recently, in his Rolf Schock Prize Lecture, Derek Parfit has suggested a novel way of avoiding the Repugnant Conclusion by introducing what he calls “imprecision” in value comparisons.  He suggests that in a range of important cases, populations of different sizes are only imprecisely comparable. Parfit suggests that this feature of value comparisons opens up a way of avoiding the Repugnant Conclusion without implying other counterintuitive conclusions, and thus solves one of the major challenges in ethics. In this paper, I shall try to clarify Parfit’s proposal and evaluate whether it will help us with the paradoxes in population ethics.