John Broome

Since the last ice age, when ice enveloped most of the northern continents, the earth has warmed by about five degrees. Within a century, it is likely to warm by another four or five. This revolution in our climate will have immense and mostly harmful effects on the lives of people not yet born. We are inflicting this harm on our descendants by dumping greenhouse gases into the atmosphere. We can mitigate the harm a little by taking measures to control our emissions of these gases, and to adapt to the changes by, for instance, building sea walls around coastlines threatened by rising sea levels. But these measures will be very expensive, and the costs will be born by us, the present generation, whereas the benefits will come to future generations. How much should we sacrifice for the sake of the future? Economists and philosophers have independently worked on the question of our responsibility to future generations. This book brings their work together and applies it to global warming. It suggests a programme for future research on the economic and ethical issues. The book is intended for economists, and for philosophers and other social scientists who have a little knowledge of economic methods.

Most properties have comparatives, which are relations. For instance, the property of width has the comparative relation denoted by `_ is wider than _'. Let us say a property is reducible to its comparative if any statement that refers to the property has the same meaning as another statement that refers to the comparative instead. Width is not reducible to its comparative. To be sure, many statements that refer to width are reducible: for instance, `The Mississippi is wide' means the same as `The Mississippi is wider than most rivers'. But some statements that refer to width are not reducible: for instance, `Electrons have zero width' is not. A property is not reducible to its comparative if it has absolute degrees, and specifically an absolute zero. A property's comparative relation places things in an order from those that have the property least to those that have it most. If there is an absolute zero point somewhere in this ordering, the property is not reducible to its comparative. For width, there is an absolute zero at one end of the ordering, so width is not reducible. The property of goodness is reducible to its comparative, betterness. In particular, there is no absolute zero of goodness. Things are ordered by betterness – some things are better than others – but nothing is absolutely good or absolutely bad. This is an exaggeration. In certain applications, goodness does have absolute degrees of a sort, and an absolute zero. For instance, it makes sense to say an event is good, and another event bad. These are absolute degrees of a sort, but they are themselves reducible to betterness. To say an event is good simply means the event is better than what would otherwise have happened. The goodness of lives has a different sort of absolute zero. Lives are ordered by betterness; some lives are better than others. We can make sense of the question `Where in this ordering is the division between lives that are good and those that are bad?' The division between good and bad lives is again reducible to betterness. To say a person's life is good means it is better that the person should continue living, rather than that she should die. Or it may mean it is better that her life should be lived rather than that it should never have been lived at all. As it is often put: a good life is a life worth living. Derek Parfit appears to attach a different sense to the idea of a good life. He appears to mean a life that contains a preponderance of good things (such as pleasure) over bad things (such as pain). If a life contains no good things and no bad things, it has zero goodness in this sense. In this sense, absolute goodness and the absolute zero of goodness are not reducible to betterness. However, this is a naturalistic sense of goodness, and it is subject to the open-question objection. If a life contains no good things and no bad things, it is an open question whether it has zero goodness. It might, for instance, be a bad thing that this life should be lived. In discussing the evil of death, some philosophers seem to have been searching for an absolute goodness that is not reducible to betterness. Thomas Nagel speaks of an asymmetry between what is good about life and what is bad about death. But if a person's life is good, that only means it would be better that she should continue living than that she should die. And if a person's death would be bad, that only means it would be worse that she should die than that she should continue living. So there can be no asymmetry.

Normative requirements are often overlooked, but they are central features of the normative world. Rationality is often thought to consist in acting for reasons, but following normative requirements is also a major part of rationality. In particular, correct reasoning – both theoretical and practical – is governed by normative requirements rather than by reasons. This article explains the nature of normative requirements, and gives examples of their importance. It also describes mistakes that philosophers have made as a result of confusing normative requirements with reasons

Two options are incommensurate in value if neither is better than the other, and if a small improvement or worsening of one does not necessarily make it determinately better or worse than the other. If a person faces a sequence of choices between incommensurate options, she may end up with a worse options than she could have had, even though none of her choices are irrational. Yet it seems that rationality should save her from this bad outcome. This is the practical problem posed by incommensurability of values, and it may be solved by a new account of practical reasoning.

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.

Some philosophers think that rationality consists in responding correctly to reasons, or alternatively in responding correctly to beliefs about reasons. This paper considers various possible interpretations of ‘responding correctly to reasons’ and of ‘responding correctly to beliefs about reasons’, and concludes that rationality consists in neither, under any interpretation. It recognizes that, under some interpretations, rationality does entail responding correctly to beliefs about reasons. That is: necessarily, if you are rational you respond correctly to your beliefs about reasons.

In 1955 John Harsanyi proved a remarkable theorem that connects general good with the personal good of individuals. This chapter interprets Harsanyi’s theorem. It explains the meaning of its conclusion, the way it links together intrapersonal and interpersonal aggregation, and in particular the link it makes between the value of avoiding risk and the value of avoiding inequality between people. It explains how the theorem connects prioritarianism with risk avoidance and utilitarianism with risk neutrality. It sets out the theorem’s premises and assesses the various objections that have been made to them. Finally, it considers how far Harsanyi’s theorem gives support to utilitarianism.

Economists can value things for cost-benefit analysis using either a structured or an unstructured approach. The first imposes some theoretical structure on the valuation; the second does not. This paper explains the difference between the approaches and examines the relative merits of each. Cost-benefit analysis may be aimed at finding what would be the best action, or alternatively at finding which action should be done in a democracy. The paper explains the difference, and argues that the appropriate aim is the first. Given that, it comes down in favour of the structured approach to valuation. As an example, it discusses different approaches to valuing life in economics.

This chapter surveys some of the issues that arise in policy making when the wellbeing of future generations must be taken into account. It analyses the discounting of future wellbeing, and considers whether it is permissible. It argues that the effects of policy on the number of future people should not be ignored, and it considers what is an appropriate basis for setting a value on these effects. It considers the implications of the non-identity effect for intergenerational justice and for the Pareto principle.

Rationality requires various things of you. For example, it requires you not to have contradictory beliefs, and to intend what you believe is a necessary means to an end that you intend. Suppose rationality requires you to F. Does this fact constitute a reason for you to F? Does it even follow from this fact that you have a reason to F? I examine these questions and reach a sceptical conclusion about them. I can find no satisfactory argument to show that either has the answer ‘yes’. I consider the idea that rationality is normative for instrumental reasons, because it helps you to achieve some of the things you ought to achieve. I also consider the idea that rationality consists in responding correctly to reasons. I reject both.

“Utility,” in plain English, means usefulness. In Australia, a ute is a useful vehicle. Jeremy Bentham specialized the meaning to a particular sort of usefulness. “By utility,” he said, “is meant that property in any object, whereby it tends to produce benefit, advantage, pleasure, good, or happiness or to prevent the happening of mischief, pain, evil, or unhappiness to the party whose interest is considered”. The “principle of utility” is the principle that actions are to be judged by their usefulness in this sense: their tendency to produce benefit, advantage, pleasure, good, or happiness. When John Stuart Mill spoke of the “perfectly just conception of Utility or Happiness, considered as the directive rule of human conduct,” he was using “Utility” as a short name for this principle. “The greatest happiness principle” was another name for it. People who subscribed to this principle came to be known as utilitarians