The Repugnant Conclusion

A Philosophical Inquiry

Christopher Cowie

• Publisher: Routledge
• Year: 2019
• ISBN:
  9780429886652
• Edition: 1
• Topic: Economics
• Subtopic: Development Economics
• Index: Economics

The Repugnant Conclusion is a controversial theorem about population size. It states that a sufficiently large population of lives that are barely worth living is better than a smaller population of high quality lives. This is highly counter-intuitive. It implies that we can improve the world by trading quality of life for quantity of lives. Can it be defended?

Christopher Cowie explores these questions and unpacks the controversies surrounding the Repugnant Conclusion. He focuses on whether the truth of the Repugnant Conclusion turns - as some have claimed - on the uncomfortable claim that many people's lives are actually bad for them and that even privileged people lead lives that are only just worth living.

Highly recommended for those interested in ethics, applied ethics and population studies The Repugnant Conclusion will also be of interest to those in related disciplines such as economics, development studies, politics and international relations.

1 Introduction

The Repugnant Conclusion is a controversial theorem about population size. It states that enormous populations of lives that are barely worth living can be – and sometimes are – better than small populations of high-quality lives. This is highly counter-intuitive. Hence, the controversial nature of the theorem. The aim of this book is to explore whether, despite this, it might nonetheless be true. More specifically, the aim is to explore a particularly striking defence of its truth. This defence is based on an uncomfortable claim about the quality of our lives. It is that many people’s lives are actually bad for them and even privileged people lead lives that are only just worth living. The thought is that if this is true, then the Repugnant Conclusion is true too.

There is a lot going on here. We need to put some foundations in place. The best place to start is with the idea that we can evaluate different populations. It is the most fundamental assumption behind all of our subsequent reasoning and argumentation. Strange though it may sound, it is something that we are all familiar with. An ordinary example illustrates. In 1800, the world’s population was close to one billion. It is now closer to eight billion and growing.¹ It is projected to continue to grow well into this century. This is one of the most serious challenges of our time. In his classic book, The Population Bomb, Paul Ehrlich gave clear voice to it:

Too many cars, too many factories, too much detergent, too many pesticides, multiplying contrails, inadequate sewage treatment plants, too little water, too much carbon dioxide – all can be traced easily to too many people.

Ehrlich 1968: 66

Ehrlich claimed that there were too many people (‘Too Many People’ is the title of part 1 of chapter 1 of his book). He has continued to voice this concern over the decades, since the publication of The Population Bomb. Economists and geographers, social commentators and politicians increasingly follow him in this. Don’t worry about the truth of Ehrlich’s claim; it may or may not be true. Instead, note an assumption that he and others are making. They are assuming that – in at least some cases – we can compare (or evaluate or rank) populations of different sizes. We can establish that some are better or worse than others. Without this assumption, they could not say that some populations are too big.

This raises an obvious question. How can we do this? What principles allow us to work out which of two or more different possible populations is better or worse?² Sometimes the comparison may seem obvious; given the earth’s current resources populations of over fifty billion will obviously be worse than populations of ten billion. Clearly articulating why this is the case is more challenging, however, and some comparisons are much less obvious. This is especially true when we are sensitive to the fact that welfare or quality of life (I use these as synonyms throughout) is likely to vary as population size varies. Suppose, for example, that we compare a population of eight billion people all of whom lead lives of a reasonably high quality with a population of ten million people, all of whom lead lives of a significantly higher quality. Which is better, and why? What about a billion people with a quality of life somewhere between these two extremes? How would this compare? Or suppose that in the near future human population can expand without constraints based on the limited resources of our planet (there are, as economists would say, no ‘externalities’). Should we then aim to populate the galaxy? Would a human population of many trillion people, all of whom lead a good quality of life, be any better than the billions that we already have? If not, why not?

Philosophers have been engaged in the search for the general principles that allow us to answer these difficult questions for the past forty years. They have not arrived at any satisfactory answers. On the contrary. Not only have they been unable to find the general principles that they are looking for, they have also generated scepticism about whether any such principles could be found. This is, in part at least, because otherwise plausible-seeming principles have a tendency to yield highly counter-intuitive consequences. One of the most troubling – and stubbornest – of all of these counter-intuitive consequences is the Repugnant Conclusion. Although it arguably dates to the great nineteenth century philosopher Henry Sidgwick, this result owes its contemporary prominence to Derek Parfit’s compelling presentation in his classic book Reasons and Persons. In Part IV of that book, Parfit noted that some very plausible reasoning about what such a principle would look like led to a very implausible conclusion indeed. He presented it 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: 388

This is the Repugnant Conclusion. As we will see below, the above quotation isn’t actually the best way of articulating it, but the basic idea comes across clearly enough nonetheless. It is that enormous populations in which everyone has a life that is barely worth living can nonetheless be better than small populations in which everyone enjoys a great quality of life. This struck Parfit as clearly false; so much so that he labelled it ‘repugnant’. It continues to strike many who encounter it today in just this way. If anything, its counter-intuitiveness probably resonates to an even greater extent today than when Parfit first published it; world population now stands at eight billion and concerns about over-population understandably occupy an increasingly prominent place in the contemporary social consciousness and political agenda – more so than when Ehrlich or Parfit were initially writing. Given this, the fact that, as Parfit demonstrated, very plausible reasoning seems to show that it is true will strike many as strongly counter-intuitive.

One of the aims of this book is to explain the ‘very plausible reasoning’ that leads to this counter-intuitive conclusion. This is the task of chapter 1. The other aim – the main aim, in fact – is to examine a particularly interesting defence of it. That defence is based on the uncomfortable truth that many people’s lives are actually bad for them and even privileged people lead lives that are only just worth living. I refer to this throughout as the Quality of Life Strategy. This is the title of chapter 2. It may not be obvious how or why this ‘uncomfortable truth’ could be a defence of the Repugnant Conclusion. To see why it could be, take a step back to think about the structure of the problem that we face. It is that extremely plausible reasoning yields an extremely counter-intuitive conclusion. The basic structure is familiar to philosophers as that of a paradox. This is a perfectly general structure of problem that appears when we think about fundamentals in many different areas of enquiry: space and time, the composition of matter, the nature of mind, and value (to name a few).³ It is surprisingly common to find that our most basic beliefs about them yield a wildly implausible result. Whatever the subject-matter, there are two ways of dealing with a paradox. One is to reject the reasoning that leads to the implausible conclusion. This requires identifying where the reasoning goes wrong. The second is to accept the conclusion. This requires explaining why it seems wildly counter-intuitive, though in fact it is not. The Quality of Life Strategy is an attempt to defend this second option. It is an attempt to explain why, though the Repugnant Conclusion seems wildly counter-intuitive, it is in fact true.

How could this be? The basic idea is as follows. The Repugnant Conclusion seems false because we imagine lives that are barely worth living as really terrible things. We imagine them as being like the lives of the most terribly unfortunate people; as, for example, lives without meaning or hope, or as lives lived below the poverty line. If that were accurate, then the Repugnant Conclusion really would be unacceptable: an enormous number of lives like these couldn’t be better than a small number of great lives. But, according to the Quality of Life Strategy, it is not accurate. When we imagine lives that are barely worth living, we should in fact imagine lives that are much better than this. We should imagine lives like those of fortunate, prosperous people. Lives without meaning or hope, or lives lived below the poverty line are worse than this. Now suppose that this is true. The Repugnant Conclusion is no longer obviously false. Its seeming falsity is the result of mis-imagining what a life that is barely worth living is in fact like. It is a result of imagining it to be worse than it in fact is. We have resolved the paradox. We can accept the Repugnant Conclusion and the plausible reasoning that it follows from.

This strategy has been defended by some of the most prominent contributors to the field. My aim is to fairly and fully present and assess it. I set out to defend it. In chapters 2 and 3, I show that it is more robust than one might think. It can – if properly understood – be defended against common criticisms. Nevertheless, in chapter 4, I argue that it fails. We cannot resolve the paradox in this way. This is disappointing. As with many purported solutions in the study of population, the real issue is that the Quality of Life Strategy has deeply implausible consequences when we attempt to generalise with it; to tease out its consequences in the context of new comparisons of populations. Two of these implausible consequences concern variants on the Repugnant Conclusion: the Very Repugnant Conclusion and the Reverse Repugnant Conclusion. I explain what these are later. The basic problem though is that the Quality of Life Strategy runs aground on them. This is not, in itself, a novel conclusion. Both the Very Repugnant Conclusion and the Reverse Repugnant Conclusion are familiar in the literature. That they represent a serious challenge to the Quality of Life Strategy is well-known. And whilst ultimately I agree, I make two novel contributions along the way. Firstly, I show that the route from the Very Repugnant Conclusion and the Reverse Repugnant Conclusion to the failure of the Quality of Life Strategy is a long and tortuous one that depends on how one reasons to the Repugnant Conclusion (a point that is often missed). Secondly, I show that there are conditions – interestingly similar conditions – under which these serious challenges could be avoided but that these conditions cannot be met. All of this is illustrated at length in chapter 4.

The roadmap is as follows. In chapter 2, I present and contextualise three basic arguments for the Repugnant Conclusion. This includes some background material on the assessment of populations (section 2.2) that, while not strictly necessary, is interesting and important nonetheless. Seasoned ‘population ethicists’ may wish to skip some of it. In chapter 3, I present, clarify and motivate the Quality of Life Strategy as a means of defending the Repugnant Conclusion. I note that there are in fact a range of different interpretations of it. I articulate the strongest. In chapter 4, I develop two objections to it – one concerning the Very Repugnant Conclusion, the other concerning the Reverse Repugnant Conclusion – and explain how a defender of the Quality of Life Strategy should respond to them. I conclude that this response is not good enough. It goes without saying that there is much ground that I am unable to cover and a great deal more that I cover more quickly than I would like. This is unavoidable. The assessment of populations – even in the highly theoretical sense that I am concerned with – is a very large field and there is a great deal of technical work that I do not touch on here. Nevertheless, my hope is that this short book can be a useful tool both for those who are new to the field or new to moral philosophy (especially chapter 2), as well as for seasoned moral philosophers and population ethicists.

Notes

1 United Nations Population Division. https://population.un.org/wpp/.

2 A further, related question is what principles allow us to work out what the optimal population size is. See e.g. Dasgupta 1969, 2005 and Greaves forthcoming.

3 See e.g. Sainsbury 2009.

2 The Repugnant Conclusion

The Repugnant Conclusion is a controversial theorem that compares the values of different populations. It tells us that:

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: 388

There are many ways of getting to this theorem; the Repugnant Conclusion is the result of several quite distinct lines of reasoning. That is perhaps one of the reasons that it is worth taking seriously. Results that can (seemingly) be derived in i...

Table of contents

• Cover
• Half-Title
• Series
• Title
• Copyright
• Dedication
• Contents
• Acknowledgements
• 1 Introduction
• 2 The Repugnant Conclusion
• 3 The Quality of Life Strategy
• 4 The Very Repugnant and Reverse Repugnant Conclusions
• 5 Conclusion
• Bibliography
• Index