Derek Parfit famously opined that causing a person to exist with a life barely worth living can be wrong, although it is not wrong for that person. This conundrum is known as the nonidentity problem. Parfit also held that persons can, in a morally relevant sense, be caused to exist in the distant future by actions that make the agent a necessary condition for a person’s existence. When these views are combined, which he did, and applied explicitly to persons with a life not worth living, which he did not, an interesting conditional conclusion can be drawn. If every family line eventually produces a person with a life not worth living, and if causing that person to exist cannot be justified by the benefits befalling others in the family line, it is always wrong to have children. Parfit did not draw this antinatalist conclusion, but an analysis of his introduction of the nonidentity problem shows that he could have. Since Parfit’s other views on population ethics continue to be discussed with relative respect, it stands to reason that the antinatalist position should be no exception. Right or wrong, it has its legitimate place in considerations concerning the future of reproduction.

Totalism states that one population is better than another iff it has higher total welfare. One counterintuitive consequence is the Repugnant Conclusion (RC). Totalism also entails that a very large population of animals with lives barely worth living is better than a smaller population of happier humans. Furthermore, the strategies that have been used to avoid the troubling normative implications of the RC do not work in the animal case, so we may have reason to bring about such a population. I introduce the notion of ‘Efficiency of Welfare Production’ – that animals of different species vary in the efficiency with which they convert resources into welfare. If we want to maximize total welfare, without any speciesist bias, we should identify which species is most efficient and try to maximize the population of that species. This has counterintuitive implications whether we accept hedonism or a more sophisticated theory of welfare.

This paper offers a unified explanation for the procreation asymmetry and the non-identity thesis – two of the most intractable puzzles in population ethics. According to the procreation asymmetry, there are moral reasons not to create lives that are not worth living but no moral reasons to create lives that are worth living. I explain the procreation asymmetry by arguing that there are moral reasons to prevent the bad, but no moral reasons to promote the good. Various explanations for the procreation asymmetry have failed to explain the non-identity thesis: if one could create a person with a good life or a different person with a better life, one has a moral reason to create the better life. I argue that reflections on the misfortune of unfulfilled potential allow us to circumvent the non-identity problem.

The valence of a life – that is, whether it is good, bad or neutral – is an important consideration in population ethics. This paper examines various definitions of valence. The main focus is ‘temporal’ definitions, which define valence in terms of the ‘shape’ of a life’s value over time. The paper argues that temporal definitions are viable only with a restricted domain, and therefore are incompatible with certain substantive theories of well-being. It also briefly considers some popular non-temporal definitions, and raises some problems for these.

David Boonin argues that in a choice between creating a person whose life would be well worth living and creating a different person whose life would be significantly worse, but still worth living, each option is morally permissible. I show that Boonin's argument for this view problematically implies that in a choice between creating a person whose life would be well worth living and creating another person whose life would not be worth living, each option is also morally permissible.

According to the Welfare Diffusion Objection, we should reject Prioritarianism because it implies the ‘desirability of welfare diffusion’: the claim that it can be better for there to be less total wellbeing spread thinly between a larger total number of people, rather than for there to be more total wellbeing, spread more generously between a smaller total number of people. I argue that while Prioritarianism does not directly imply the desirability of welfare diffusion, Prioritarians are nevertheless implicitly committed to certain principles for comparing different-number populations which, together with the Prioritarian same-person axiology, imply the desirability of welfare diffusion.

Is the procreation asymmetry intuitively supported? According to a recent article in this journal, an experimental study suggests the opposite. Dean Spears (2020) claims that nearly three-quarters of participants report that there is a reason to create a person just because that person’s life would be happy. In reply, I argue that various confounding factors render the study internally invalid. More generally, I show how one might come to adopt the procreation asymmetry for the wrong reasons by misinterpreting one’s intuitions.

According to the Asymmetry, we’ve strong moral reason to prevent miserable lives from coming into existence, but no moral reason to bring happy lives into existence. This procreative asymmetry is often thought to be part of commonsense morality, however theoretically puzzling it might prove to be. I argue that this is a mistake. The Asymmetry is merely prima facie intuitive, and loses its appeal on further reflection. Mature commonsense morality recognizes no fundamental procreative asymmetry. It may recognize some superficially similar theses, but we will see that they derive from more familiar principles, and are compatible with there being moral reason to bring happy lives into existence.

What moral reasons, if any, do we have to ensure the long-term survival of humanity? This article contrastively explores two answers to this question: according to the first, we should ensure the survival of humanity because we have reason to maximize the number of happy lives that are ever lived, all else equal. According to the second, seeking to sustain humanity into the future is the appropriate response to the final value of humanity itself. Along the way, the article discusses various issues in population axiology, particularly the so-called Intuition of Neutrality and John Broome’s ‘greediness objection’ to this intuition.

Population ethics is widely considered to be exceptionally important and exceptionally difficult. One key source of difficulty is the conflict between certain moral intuitions and analytical results identifying requirements for rational (in the sense of complete and transitive) social choice over possible populations. One prominent such intuition is the Asymmetry, which jointly proposes that the fact that a possible child’s quality of life would be bad is a normative reason not to create the child, but the fact that a child’s quality of life would be good is not a reason to create the child. This paper reports a set of questionnaire experiments about the Asymmetry in the spirit of economists’ empirical social choice. Few survey respondents show support for the Asymmetry; instead respondents report that expectations of a good quality of life are relevant. Each experiment shows evidence (among at least some participants) of dual-process moral reasoning, in which cognitive reflection is statistically associated with reporting expected good quality of life to be normatively relevant. The paper discusses possible implications of these results for the economics of population-sensitive social welfare and for the conflict between moral mathematics and population intuition.

Critical-Range Utilitarianism is a variant of Total Utilitarianism which can avoid both the Repugnant Conclusion and the Sadistic Conclusion in population ethics. Yet Standard Critical-Range Utilitarianism entails the Weak Sadistic Conclusion, that is, it entails that each population consisting of lives at a bad well-being level is not worse than some population consisting of lives at a good well-being level. In this paper, I defend a version of Critical-Range Utilitarianism which does not entail the Weak Sadistic Conclusion. This is made possible by what I call ‘undistinguishedness’, a fourth category of absolute value in addition to goodness, badness, and neutrality.

In this article we distinguish two versions of the non-identity problem: one involving positive well-being and one involving negative well-being. Intuitively, there seems to be a difference between the two versions of the problem. In the negative case it is clear that one ought to cause the better-off person to exist. However, it has recently been suggested that this is not so in the positive case. We argue that such an asymmetrical treatment of the two versions should be rejected and that this is evidence against views according to which it is permissible to cause the less well-off person to exist in the positive non-identity case.

Standard lessons from economics tell us that an externality creates inefficiency, and that this inefficiency can be removed by internalizing the externality. This papers considers how successfully these lessons can be extended to intergenerational externalities such as emissions of greenhouse gas. For intergenerational externalities, the standard lessons involve comparisons between states whose populations of people differ, either in their identities or their numbers. Common notions of efficiency break down in these comparisons. This paper supplies a new notion of efficiency that allows the lessons to survive, but at the cost of reducing their practical significance.