According to a recent survey, Americans and Europeans see income and wealth inequality as the greatest threat to the world – a threat greater than climate change, nuclear armament, religious and ethnic hatred, and illnesses such as AIDS (2014 Global Attitudes survey, PEW Research Center). Although inequality in income and wealth is widely viewed as morally problematic, it is not always so clear why this is the case. Sometimes, objections to such inequality seem to amount to little more than envy: Those who have less, want to have as much as those who have more. Other objections turn out to really be objections to the consequences of some having more than others. If these consequences could be mitigated without eliminating the inequality, then there would be no moral reason against it. There is, for instance, strong empirical evidence that inequality in income and wealth has negative health consequences for those who have less. If these could be eliminated without reducing the inequality, then health consequences are not a reason to object to it. This raises the question whether there are reasons why inequality in income and wealth is, in itself, objectionable. Why does inequality matter? This is the question that exercises T.M. Scanlon in his latest book.

The project of the book is admirably ambitious. Scanlon aims to uncover a set of distinctive reasons for objecting to inequality that not only capture what is morally problematic about inequality in income and wealth, but also about ‘[r]acial inequality’, ‘various forms of inequality between men and women’, and ‘inequality between people in different countries’ (4). According to him, these inequalities are objectionable for different combinations of reasons, and it is important to be precise on what these are. To make sure that he can discuss each issue in sufficient depth, Scanlon limits himself to six reasons why inequality matters that are of special interest to philosophers, because ‘there are interesting normative questions about the values that underlie them’ (10). All of these six reasons are relational: they ‘depend on the way that an inequality affects or arises from the relations between individuals’ (152).

The book contains an introduction (chapter 1), eight substantive chapters (chapters 2–9), and a conclusion (chapter 10). Six of the substantive chapters are devoted to the six reasons for objecting to inequality that Scanlon identifies. The first reason is that a government or an institution treats with unequal concern people to whom an equal benefit is owed (chapter 2). According to Scanlon, this occurs, for instance, when there are fewer safeguards against wrongful conviction for the poor, because everyone is owed such safeguards equally (16). The second distinctive reason he identifies is that people are denied equal status by not taking them to be eligible for important goods – including being a co-worker, potential friend, or neighbor – on the basis of morally arbitrary characteristics, such as their gender or race (chapter 3). The third and fourth reason for objecting to inequality are both part of Scanlon's account of equality of opportunity. People have no equal opportunity, and hence a legitimate ground to object to inequality, when the selection for positions of advantage (such as the position of judge or university professor) is procedurally unfair because characteristics of candidates are taken into account that are irrelevant for the position in question (chapter 4). People also have no equal opportunity when there is no substantive opportunity to do well in the selection for positions of advantage (chapter 5), for instance because their parents could not afford higher quality education for them (67).

The fifth distinctive reason for objecting to inequality that Scanlon identifies is that it undermines political fairness (chapter 6). This is the case when the rich, because of their wealth, have a greater capacity to influence government officials to make decisions that favor their interests, and have a higher chance of being successful candidates for public office (93). Finally, it is objectionable when the costs of economic productivity are distributed unequally (chapter 9). There is no good reason, according to Scanlon, why the capacity of firms to efficiently adjust to changing economic circumstances by hiring and firing people should be borne only by workers; proper safeguards have to be put in place to prevent them from losing control over their lives in case they are fired (148). In the remaining two substantive chapters, Scanlon rejects two common arguments against reducing inequalities: that it constitutes an unacceptable interference with people's liberty (chapter 7), and that it takes away from people what they justly deserve (chapter 8).

One of the virtues of the book is that Scanlon manages to connect contemporary political and societal debates on inequality with philosophical discussions. He does so by starting nearly every chapter with an argument that is commonly made in favor of (or against) the pursuit of equality, and then spending the remainder of the chapter carefully dissecting it. In chapter 7, for instance, Scanlon discusses the idea that the promotion of equality through a system of redistributive taxes and transfers constitutes an unacceptable interference with a person's liberty, because it takes away income that people have a natural right to. He points out that this argument rests on a confusion between the importance of property rights themselves, and the importance of non-interference with the interests that the property rights are meant to protect, such as the interest in having control over the objects required to meet one's basic needs (106). This response, as Scanlon acknowledges, is not a new one – Liam Murphy and Thomas Nagel have made a similar argument before in The Myth of Ownership. It is nonetheless good to repeat it, in my view, because the misguided idea that one has a natural right to one's income still appears to be quite widespread, especially in the United States.

In fact, a number of the arguments that Scanlon discusses in this new book are, as he acknowledges throughout in footnotes, restatements of arguments that have already been defended elsewhere, especially in his own earlier work and the work of his former colleague, John Rawls. Examples include the discussion of status inequality in chapter 2 (which overlaps with Rawls's discussion in chapter 8 of A Theory of Justice, and Scanlon's discussion in chapter 2 of What We Owe To Each Other), the account of procedural fairness in chapter 4 (which overlaps with Rawls's discussion in chapter 2 of A Theory of Justice), and the objections to the idea that inequalities can be deserved (which overlaps with Scanlon's ‘Giving Desert its Due’ in Basic Desert, Reactive Attitudes and Free Will). This may be somewhat of a disappointment to those who are familiar with Rawls's and Scanlon's work. However, the book is nonetheless worthwhile, for three reasons.

First of all, the arguments that Scanlon restates are spread over a number of articles and books, and, given the immense current interest in inequality, it is helpful to have one book that provides an anatomy of the ideal of equality according to a central liberal egalitarian view. Secondly, some of the arguments Scanlon discusses are often misunderstood – and he corrects a number of these misunderstandings. He points out, for instance, that many people mistakenly think that equality of opportunity is a sufficient condition for inequalities to be justified, whereas it should really be thought of only as a necessary condition, and a very demanding one at that (40). Scanlon, finally, does not only acknowledge, as many philosophers do, that the moral permissibility of inequalities often depends on empirical facts, but also actually discusses some of these facts, especially in chapter 9. In that chapter, he claims, among other things, that the efficiency argument for high CEO pay in especially the United States is invalid on empirical grounds, and that hence such salaries cannot be justified by the benefits they are supposed to generate for all (145). Such attention to empirical facts is welcome, as it may help philosophers in connecting their work more to political and societal discussions.

There are parts of the book where further discussion would have been welcome. It would, for instance, have been interesting if Scanlon had devoted some more time to showing that the arguments in the book apply to as large a range of inequalities as he claims they do. Scanlon claims in the introduction that the reasons for objecting to inequality that he identifies also apply to the ‘various forms of inequality between men and women’, and ‘inequality between people in different countries’ (4), but only discusses these inequalities briefly throughout the book. It may well be that his six reasons indeed also apply to such inequalities – but it would have added to the credibility of that claim if this had been demonstrated more.

Another issue is that Scanlon's views on desert may not be fully charitable towards all the possible interpretations of desert that are available (chapter 8). He claims, with little supporting argument, that desert claims are made appropriate ‘simply by facts about what that person is like or has done’, but not by whether these characteristics or acts are under a person's control (121, his emphasis). Many philosophers believe, however, that such a view of desert is quite implausible if desert is to be a principle of distributive justice, and that alternative, control-sensitive views of desert can be formulated (see, for instance, chapter 1 of Serena Olsaretti's Liberty, Desert, and the Market). Hence, Scanlon's rejection of desert-based justifications for economic inequalities would have been stronger if he had also elaborated on his objections to control-sensitive views of desert.

Thirdly, the question why inequality matters seems, at times, to be so closely related to the question when it matters that some further reflection on the latter would have been helpful. In chapter 2, for example, Scanlon argues that a distinctive reason for objecting to inequality is that an institution treats with unequal concern people to whom an equal benefit is owed. He ends this chapter by pointing out that there are various good reasons why people could be owed an unequal benefit. It may, for instance, be compatible with equal concern to provide a certain area with faster internet if that is required for a scientific research community that works there (20). Scanlon does little to clarify, however, when exactly a reason why people are owed an unequal benefit is sufficient for treating them with unequal concern. An answer to that question would have helped to understand better what the requirement of equal concern dictates and detect violations of it in the real world.

Let me end this review with a small mystery about the book that I have been unable to solve. When I first saw the book cover, I thought that it depicts (or, at least, hints at) a Lorenz curve – a graph developed in the early 1900s by Max O. Lorenz to show the distribution of income (or wealth) amongst a population. A few other readers thought that I was reading too much into the cover. Regardless of what the correct interpretation is, however, it is clear that the Lorenz curve for both income and wealth in the United Kingdom and the United States has shifted outwards during the past four decades, indicating greater inequality, and is likely to continue shifting outwards during the next. Scanlon's Why Does Inequality Matter? offers an excellent framework for discussing why this rise in inequality could be objectionable, and I hope that it will be read by many. The book will be especially worthwhile to political philosophers who are working on questions of inequality, but may also be a source of inspiration to social scientists who are willing to take an interest in normative questions.