Population axiology concerns how to evaluate populations in terms of their moral goodness, that is, how to order populations by the relations “is better than” and “is as good as”. The task 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, and their identities may vary. So far, this field has largely ignored issues about uncertainty and the conditions that have been discussed mostly pertain (...) to the ranking of risk-free outcomes. Most public policy choices, however, are decisions under uncertainty, including policy choices that affect the size of a population. Here, we shall address the question of how to rank population prospects—that is, alternatives that contain uncertainty as to which population they will bring about—by the relations “is better than” and “is as good as”. 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 praised for avoiding in the risk-free settings. Finally, we identify an intuitive adequacy condition that, we contend, should be satisfied by any population prospect axiology, and show how given this condition, the impossibility theorems in population axiology can be extended to (non-trivial) impossibility theorems for population prospect axiology. (shrink)

I present a new argument for the repugnant conclusion. The core of the argument is a risky, intrapersonal analogue of the mere addition paradox. The argument is important for three reasons. First, some solutions to Parfit’s original puzzle do not obviously generalize to the intrapersonal puzzle in a plausible way. Second, it raises independently important questions about how to make decisions under uncertainty for the sake of people whose existence might depend on what we do. And, third, it suggests various (...) difficulties for leading views about the value of a person’s life compared to her nonexistence. (shrink)

Population axiology is the study of the conditions under which one state of affairs is better than another, when the states of affairs in ques- tion may differ over the numbers and the identities of the persons who ever live. Extant theories include totalism, averagism, variable value theories, critical level theories, and “person-affecting” theories. Each of these the- ories is open to objections that are at least prima facie serious. A series of impossibility theorems shows that this is no coincidence: (...) it can be proved, for various sets of prima facie intuitively compelling desiderata, that no axiology can simultaneously satisfy all the desiderata on the list. One’s choice of population axiology appears to be a choice of which intuition one is least unwilling to give up. (shrink)

This book presents an exploration of the idea of the common or social good, extended so that alternatives with different populations can be ranked. The approach is, in the main, welfarist, basing rankings on the well-being, broadly conceived, of those who are alive. The axiomatic method is employed, and topics investigated include: the measurement of individual well-being, social attitudes toward inequality of well-being, the main classes of population principles, principles that provide incomplete rankings, principles that rank uncertain alternatives, best choices (...) from feasible sets, and applications. The chapters are divided, with mathematical arguments confined to the second part. The first part is intended to make the arguments accessible to a more general readership. Although the book can be read as a defense of the critical-level generalized-utilitarian class of principles, comprehensive examinations of other classes are included. (shrink)

According to the Repugnant Conclusion: Compared with the existence of many people who would all have some very high quality of life, there is some much larger number of people whose existence would be better, even though these people would all have lives that were barely worth living. I suggest some ways in which we might be able to avoid this conclusion. I try to defend a strong form of lexical superiority.

Esteemed philosopher John Broome avoids the familiar ideological stances on climate change policy and examines the issue through an invigorating new lens. As he considers the moral dimensions of climate change, he reasons clearly through what universal standards of goodness and justice require of us, both as citizens and as governments. His conclusions—some as demanding as they are logical—will challenge and enlighten. Eco-conscious readers may be surprised to hear they have a duty to offset all their carbon emissions, while policy (...) makers will grapple with Broome’s analysis of what if anything is owed to future generations. From the science of greenhouse gases to the intricate logic of cap and trade, Broome reveals how the principles that underlie everyday decision making also provide simple and effective ideas for confronting climate change. Climate Matters is an essential contribution to one of the paramount issues of our time. (shrink)

Is there some large number of very mild hangnail pains, each experienced by a separate person, which would be worse than two years of excruciating torture, experienced by a single person? Many people have the intuition that the answer to this question is No. However, a host of philosophers have argued that, because we have no intuitive grasp of very large numbers, we should not trust such intuitions. I argue that there is decent intuitive support for the No answer, which (...) does not depend on our intuitively grasping or imagining very large numbers. (shrink)

Act Utilitarianisms divide into Total and Average versions. Total versions seem to imply Parfit’s “Repugnant Conclusion”. Average versions are proposed in part to avoid the Repugnant Conclusion, but these are subject to “Mere Addition” arguments as detailed by Hudson in “The Diminishing Marginal Value of Happy People”. Thus, various intermediate versions of utilitarianism, such as the one investigated by Hurka in “Value and Population Size”, take on interest. But Hudson argues that such compromise theories are subject to the mere addition (...) arguments, and are therefore no improvement over Average Utilitarianism. I disagree: some such compromise solutions escape Hudson’s Mere Addition arguments. (shrink)

This paper re-examines the welfare economics of risk. It singles out a class of criteria, the “expected equally-distributed equivalent”, as the unique class which avoids serious drawbacks of existing approaches. Such criteria behave like ex-post criteria when the final statistical distribution of wellbeing is known ex ante, and like ex-ante criteria when risk generates no inequality. The paper also provides a new result on the tension between inequality aversion and respect of individual ex ante preferences, in the vein of Harsanyi’s (...) aggregation theorem. (shrink)

We are often faced with choices that involve the weighing of people's lives against each other, or the weighing of lives against other good things. These are choices both for individuals and for societies. A person who is terminally ill may have to choose between palliative care and more aggressive treatment, which will give her a longer life but at some cost in suffering. We have to choose between the convenience to ourselves of road and air travel, and the lives (...) of the future people who will be killed by the global warming we cause, through violent weather, tropical disease, and heat waves. We also make choices that affect how many lives there will be in the future: as individuals we choose how many children to have, and societies choose tax policies that influence people's choices about having children. These are all problems of weighing lives. How should we weigh lives? Weighing Lives develops a theoretical basis for answering this practical question. It extends the work and methods of Broome's earlier book Weighing Goods to cover the questions of life and death. Difficult problems come up in the process. In particular, Weighing Lives tackles the well-recognized, awkward problems of the ethics of population. It carefully examines the common intuition that adding people to the population is ethically neutral - neither a good nor a bad thing - but eventually concludes this intuition cannot be fitted into a coherent theory of value. In the course of its argument, Weighing Lives examines many of the issues of contemporary moral theory: the nature of consequentialism and teleology; the transitivity, continuity, and vagueness of betterness; the quantitative conception of wellbeing; the notion of a life worth living; the badness of death; and others. This is a work of philosophy, but one of its distinctive features is that it adopts some of the precise methods of economic theory (without introducing complex mathematics). Not only philosophers, but also economists and political theorists concerned with the practical question of valuing life, should find the book's conclusions highly significant to their work. (shrink)

I defend the 'Repugnant' Conclusion that for any possible population of happy people, a population containing a sufficient number of people with lives barely worth living would be better. Four lines of argument converge on this conclusion, and the conclusion has a simple, natural theoretical explanation. The opposition to the Repugnant Conclusion rests on a bare appeal to intuition. This intuition is open to charges of being influenced by multiple distorting factors. Several theories of population ethics have been devised to (...) avoid the Repugnant Conclusion, but each generates even more counterintuitive consequences. The intuition opposing the Repugnant Conclusion is thus among the best candidates for an intuition that should be revised. (shrink)

Challenging, with several powerful arguments, some of our deepest beliefs about rationality, morality, and personal identity, Parfit claims that we have a false view about our own nature. It is often rational to act against our own best interersts, he argues, and most of us have moral views that are self-defeating. We often act wrongly, although we know there will be no one with serious grounds for complaint, and when we consider future generations it is very hard to avoid conclusions (...) that most of us will find very disturbing. (shrink)

Parfit's requirements for an ideal Theory X cannot be fully met since the Mere Addition Principle and Non-Antiegalitarianism imply the Repugnant Conclusion: Theory X does not exist. However, since the Repugnant Conclusion is really compelling, the Impersonal Total Principle should be adopted for impartial comparisons concerning future generations. Nevertheless, where our own interests are affected, we may yet choose to be partial, trading off our concern for future goodness with our self-interests. Theory X' meets all Parfit's requirements except the Mere (...) Addition Principle in less compelling cases. (shrink)

The spectre of the repugnant conclusion and the search for a population axiology that avoids it has endured as a focus of population ethics. This is in part because the repugnant conclusion is often interpreted as a defining problem for totalism, while the implications of averagism and related views are taken to illustrate the theoretical cost of avoiding the repugnant conclusion. However, we show that this interpretation cannot be sustained unless one focuses only on a special case of the repugnant (...) conclusion: namely, the subset of instances of the repugnant conclusion where there is no portion of the population unaffected by the choice between population outcomes (as in Derek Parfit’s original illustration). To avoid an inappropriate focus on only this proper subset of instances of the repugnant conclusion, we formulate a general characterization of the repugnant conclusion. We then prove formally that all leading welfarist axiologies imply this conclusion, including averagism and Ng’s Theory X0 , including probabilistic and ‘very repugnant’ variants that involve the addition of negative lives. We then prove that the full range of axiologies considered by population ethics each imply an extended version of the repugnant conclusion, including axiologies that are incomplete, intransitive, rank-dependent, person-affecting, and/or pluralist. The upshot is that the repugnant conclusion does not ultimately tell against any approach to axiology, and the methodological requirement to avoid the repugnant conclusion should be dropped from population axiology. (shrink)

In a series of articles on population theory, culminating in his 1984 b00k Reasons and Persons, Dcrck Pariit presented dilemmas for utilitarian and conscqucntialist moral theories.] ParHt’s work has led to rcncwcd interest in thc theory of optimal population. More generally, Pariit is searching for a general theory of bcncHcencc—"Theory X"——that also will covcr population comparisons. Theory X corresponds to Kenneth Arrow’s notion of a social welfare function—both attempt t0 provide 21 generic formula or algorithm for ranking social outcomes on (...) the basis of their characteristics. (shrink)

Derek Parfit has famously pointed out that ‘total’ utilitarian views, such as classical hedonistic utilitarianism, lead to the conclusion that, to each population of quite happy persons there corresponds a more extensive population with people living lives just worth living, which is better. In particular, 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. This world is better if the sum total of well-being is great enough, and it is great enough if only enough sentient beings inhabit it. This conclusion has been considered by Parfit and others to be ‘repugnant’. (shrink)

Future population growth is uncertain and matters for climate policy: higher growth entails more emissions and means more people will be vulnerable to climate-related impacts. We show that how future population is valued importantly determines mitigation decisions. Using the Dynamic Integrated Climate-Economy model, we explore two approaches to valuing population: a discounted version of total utilitarianism (TU), which considers total wellbeing and is standard in social cost of carbon dioxide (SCC) models, and of average utilitarianism (AU), which ignores population size (...) and sums only each time period’s discounted average wellbeing. Under both approaches, as population increases the SCC increases, but optimal peak temperature decreases. The effect is larger under TU, because it responds to the fact that a larger population means climate change hurts more people: for example, in 2025, assuming the United Nations (UN)-high rather than UN-low population scenario entails an increase in the SCC of 85% under TU vs. 5% under AU. The difference in the SCC between the two population scenarios under TU is comparable to commonly debated decisions regarding time discounting. Additionally, we estimate the avoided mitigation costs implied by plausible reductions in population growth, finding that large near-term savings ($billions annually) occur under TU; savings under AU emerge in the more distant future. These savings are larger than spending shortfalls for human development policies that may lower fertility. Finally, we show that whether lowering population growth entails overall improvements in wellbeing—rather than merely cost savings—again depends on the ethical approach to valuing population. (shrink)

On an act utilitarian view it is morally permissible if not obligatory to choose to perform an action which contributes as much as any other action to the total happiness of all those capable of enjoying happiness. As the view has just been stated, however, there is some question of how we are to understand the phrase “all those capable of enjoying happiness”. For even leaving aside the possibility that animals or spirits might be included, there is still the matter (...) of the size of the population of humans “capable of enjoying happiness”. Furthermore, among our ethical decisions themselves are decisions which would cause a decrease or increase in population and which in perhaps even more specific ways determine the applicability of this phrase “all those capable of enjoying happiness”. According to the socalled classical or total utilitarian principle, the phrase in question is understood as describing some population whose existence will enable one to maximize the net amount of happiness. For on the classical principle what one is obligated to do is simply to maximize net happiness. (shrink)