Many believe that we ought to save a large number from being permanently bedridden rather than save one from death. Many also believe that we ought to save one from death rather than a multitude from a very minor harm, no matter how large this multitude. I argue that a principle I call “Aggregate Relevant Claims” satisfactorily explains these judgments. I offer a rationale for this principle and defend it against objections.

Suppose that you must make choices that may influence the well-being and the identities of the people who will exist, though not the number of people who will exist. How ought you to choose? This paper answers this question. It argues that the currency of distributive ethics in such cases is a combination of an individual’s final well-being and her expected well-being conditional on her existence. It also argues that this currency should be distributed in an egalitarian, rather than a (...) prioritarian, manner. (shrink)

We argue that deliberative decision-making that is inclusive, transparent and accountable can contribute to more trustworthy and legitimate decisions on difficult ethical questions and political trade-offs during the pandemic and beyond.

We argue that there is a marked shift in the moral weight of an increment in a person's well-being when one moves from a case involving only intra-personal trade-offs to a case involving only inter-personal trads-offs. This shift, we propose, is required by the separateness of persons. We also argue that the Priority View put forward by Parfit cannot account for such a shift. We also outline two alternative views, an egalitarian view and a claims-based view, that can account for (...) this shift. (shrink)

Policy-makers must sometimes choose between an alternative which has somewhat lower expected value for each person, but which will substantially improve the outcomes of the worst off, or an alternative which has somewhat higher expected value for each person, but which will leave those who end up worst off substantially less well off. The popular ex ante Pareto principle requires the choice of the alternative with higher expected utility for each. We argue that ex ante Pareto ought to be rejected (...) because it conflicts with the requirement that, when possible, one ought to decide as one would with full information. We apply our argument in an analysis of US policy on screening for breast cancer. -/- . (shrink)

We discuss two leading theories of distributive justice: egalitarianism and prioritarianism. We argue that while each has particular merits and shortcomings, egalitarian views more fully satisfy a key requirement of distributive justice: respect for both the unity of the individual and the separateness of persons.

In 'Rethinking the Good', Larry Temkin makes two core claims. First, the goodness of a distribution is sometimes ‘essentially comparative’ – it sometimes depends on which alternative distribution(s) it is compared to. Second, such cases threaten the transitivity of ‘all things considered better than’. I argue that the goodness of a distribution may indeed depend on what other distributions are feasible. But contrary to Temkin, I also argue that transitivity holds even when the goodness of a distribution depends on the (...) feasible set of which it is a member. (shrink)

The difference between the unity of the individual and the separateness of persons requires that there be a shift in the moral weight that we accord to changes in utility when we move from making intrapersonal tradeoffs to making interpersonal tradeoffs. We examine which forms of egalitarianism can, and which cannot, account for this shift. We argue that a form of egalitarianism which is concerned only with the extent of outcome inequality cannot account for this shift. We also argue that (...) a view which is concerned with both outcome inequality and with the unfairness of inequality in individuals‘ expected utilities can account for this shift. Finally, we limn an alternative view, on.. (shrink)

Decision-makers face severe uncertainty when they are not in a position to assign precise probabilities to all of the relevant possible outcomes of their actions. Such situations are common—novel medical treatments and policies addressing climate change are two examples. Many decision-makers respond to such uncertainty in a cautious manner and are willing to incur a cost to avoid it. There are good reasons for taking such an uncertainty-averse attitude to be permissible. However, little work has been done to incorporate it (...) into an egalitarian theory of distributive justice. We aim to remedy this lack. We put forward a novel, uncertainty-averse egalitarian view. We analyse when the aims of reducing inequality and limiting the burdens of severe uncertainty are congruent and when they conflict, and highlight practical implications of the proposed view. We also demonstrate that if uncertainty aversion is permissible, then utilitarians must relinquish a favourite argument against egalitarianism. (shrink)

When one faces competing claims of varying strength on public resources for health, which claims count? This paper proposes the following answer. One should count, or aggregate, a person’s claim just in case one could sympathize with her desire to prioritize her own claim over the strongest competing claim. It argues that this principle yields appealing case judgments and has a plausible grounding in both sympathetic identification with each person, taken separately, and respect for the person for whom most is (...) at stake. It also defends this principle against several heretofore unanswered objections. (shrink)

We use probability-matching variations on Ellsberg’s single-urn experiment to assess three questions: (1) How sensitive are ambiguity attitudes to changes from a gain to a loss frame? (2) How sensitive are ambiguity attitudes to making ambiguity easier to recognize? (3) What is the relation between subjects’ consistency of choice and the ambiguity attitudes their choices display? Contrary to most other studies, we find that a switch from a gain to a loss frame does not lead to a switch from ambiguity (...) aversion to ambiguity neutrality and/or ambiguity seeking. We also find that making ambiguity easier to recognize has little effect. Finally, we find that while ambiguity aversion does not depend on consistency, other attitudes do: consistent choosers are much more likely to be ambiguity neutral, while ambiguity seeking is much more frequent among highly inconsistent choosers. (shrink)

I outline and defend two egalitarian theories, which yield distinctive and, I argue, complementary answers to why health-related inequalities matter: a brute luck egalitarian view, according to which inequalities due to unchosen, differential luck are bad because unfair, and a social egalitarian view, according to which inequalities are bad when and because they undermine people’s status as equal citizens. These views identify different objects of egalitarian concern: the brute luck egalitarian view directs attention to health-related well-being, while social egalitarianism focuses (...) on health-related capabilities that are central to a person’s status as a citizen. I argue that both views are correct and should jointly guide priority-setting in health. (shrink)

Experimental results on the Ellsberg paradox typically reveal behavior that is commonly interpreted as ambiguity aversion. The experiments reported in the current paper find the objective probabilities for drawing a red ball that make subjects indifferent between various risky and uncertain Ellsberg bets. They allow us to examine the predictive power of alternative principles of choice under uncertainty, including the objective maximin and Hurwicz criteria, the sure-thing principle, and the principle of insufficient reason. Contrary to our expectations, the principle of (...) insufficient reason performed substantially better than rival theories in our experiment, with ambiguity aversion appearing only as a secondary phenomenon. (shrink)

This article criticises one of Stuart Rachels' and Larry Temkin's arguments against the transitivity of 'better than'. This argument invokes our intuitions about our preferences of different bundles of pleasurable or painful experiences of varying intensity and duration, which, it is argued, will typically be intransitive. This article defends the transitivity of 'better than' by showing that Rachels and Temkin are mistaken to suppose that preferences satisfying their assumptions must be intransitive. It makes cler where the argument goes wrong by (...) showing that it is a version of Zeno's paradox of Achilles and the Tortoise. (shrink)

A persistent argument against the transitivity assumption of rational choice theory postulates a repeatable action that generates a significant benefit at the expense of a negligible cost. No matter how many times the action has been taken, it therefore seems reasonable for a decision-maker to take the action one more time. However, matters are so fixed that the costs of taking the action some large number of times outweigh the benefits. In taking the action some large number of times on (...) the grounds that the benefits outweigh the costs every time, the decision-maker therefore reveals intransitive preferences, since once she has taken it this large number of times, she would prefer to return to the situation in which she had never taken the action at all. We defend transitivity against two versions of this argument: one in which it is assumed that taking the action one more time never has any perceptible cost, and one in which it is assumed that the cost of taking the action, though (sometimes) perceptible, is so small as to be outweighed at every step by the significant benefit. We argue that the description of the choice situation in the first version involves a contradiction. We also argue that the reasoning used in the second version is a form of similarity-based decision-making. We argue that when the consequences of using similarity-based decision-making are brought to light, rational decision-makers revise their preferences. We also discuss one method that might be used in performing this revision. (shrink)

Can we trust our intuitive judgments of right and wrong? Are moral judgements objective? What reason do we have to do what is right and avoid doing what is wrong? In Conversations on Ethics, Alex Voorhoeve elicits answers to these questions from eleven outstanding philosophers and social scientists: -/- Ken Binmore; Philippa Foot; Harry Frankfurt; Allan Gibbard; Daniel Kahneman; Frances Kamm; Alasdair MacIntyre; T. M. Scanlon; Peter Singer; David Velleman; Bernard Williams. -/- The exchanges are direct, open, and sharp, and (...) give a clear account of these thinkers' core ideas about ethics. They also provide unique insights into their intellectual development - how they became interested in ethics, and how they conceived the ideas for which they became famous. Conversations on Ethics will engage anyone interested in moral philosophy. (shrink)

How should governments balance saving people from very large individual disease burdens (such as an early death) against saving them from middling burdens (such as erectile dysfunction) and minor burdens (such as nail fungus)? This chapter considers this question through an analysis of a priority-setting proposal in the Netherlands, on which avoiding a multitude of middling burdens takes priority over saving one person from early death, but no number of very small burdens can take priority over avoiding one death. It (...) argues that there is some, albeit imperfect, evidence of substantial public support for such a policy. Furthermore, it provides a principled rationale for it in terms of respect for the person who faces the largest burden. (shrink)

In some severely uncertain situations, exemplified by climate change and novel pandemics, policymakers lack a reasoned basis for assigning probabilities to the possible outcomes of the policies they must choose between. I outline and defend an uncertainty averse, egalitarian approach to policy evaluation in these contexts. The upshot is a theory of distributive justice which offers especially strong reasons to guard against individual and collective misfortune.

This report by the WHO Consultative Group on Equity and Universal Health Coverage addresses how countries can make fair progress towards the goal of universal coverage. It explains the relevant tradeoffs between different desirable ends and offers guidance on how to make these tradeoffs.

A possible person’s conditional expected well-being is what the quality of their prospects would be if they were to come into existence. This paper examines the role that this form of expected well-being should play in distributing benefits among prospective people and in deciding who to bring into existence. It argues for a novel egalitarian view on which it is important to ensure equality in people’s life prospects, not merely between actual individuals, but also between all individuals who, given our (...) choices, have a chance of coming into existence. The paper argues that such egalitarianism for prospective people springs from equal concern for each person and has plausible implications. It further shows that it has a rationale in respect for both the unity of the individual and the separateness of persons. Finally, it defends this view against a key objection and shows it is superior to a rival view. (shrink)

All conceptions of equal opportunity draw on some distinction between morally justified and unjustified inequalities. We discuss how this distinction varies across a range of philosophical positions. We find that these positions often advance equality of opportunity in tandem with distributive principles based on merit, desert, consequentialist criteria or individuals' responsibility for outcomes. The result of this amalgam of principles is a festering controversy that unnecessarily diminishes the widespread acceptability of opportunity concerns. We therefore propose to restore the conceptual separation (...) of opportunity principles concerning unjustified inequalities from distributive principles concerning justifiable inequalities. On this view, equal opportunity implies that that morally irrelevant factors should engender no differences in individuals' attainment, while remaining silent on inequalities due to morally relevant factors. We examine this idea by introducing the principle of ‘opportunity dominance' and explore in a simple application to what extent this principle may help us arbitrate between opposing distributive principles. We also compare this principle to the selection rules developed by John Roemer and Dirk Van de Gaer. (shrink)

We offer a summary of the WHO Report "Making Fair Choices on the Path to Universal Health Coverage".

If a potential person would have a good life if he were to come into existence, can we coherently regard his coming into existence as better for him than his never coming into existence? And can we regard the situation in which he never comes into existence as worse for him? In this paper, we argue that both questions should be answered affirmatively. We also explain where prominent arguments to differing conclusions go wrong. Finally, we explore the relevance of our (...) answers to issues in population ethics. (shrink)

Stuart Rachels and Larry Temkin have offered a purported counter-example to the acyclicity of the relationship 'all things considered better than'. This example invokes our intuitive preferences over pairs of alternatives involving a single person's painful experiences of varying intensity and duration. These preferences, Rachels and Temkin claim, are confidently held, entirely reasonable, and cyclical. They conclude that we should drop acyclicity as a requirement of rationality. I argue that, together with the findings of recent research on the way people (...) evaluate episodes of pain, the use of a heuristic known as similarity-based decision-making explains why our intuitive preferences may violate acyclicity in this example. I argue that this explanation should lead us to regard these preferences with suspicion, because it indicates that they may be the result of one or more biases. I conclude that Rachels' and Temkin's example does not provide sufficient grounds for rejecting acyclicity. (shrink)

Suppose one can fully alleviate either the very large individual health burdens of a first group or instead the significantly lesser burdens of a second group that is at least as numerous. In such cases, the most commonly applied principles for priority setting in health have two characteristics. First, when both groups are equally large, they prioritize alleviating the plight of the more severely burdened. Second, when both groups differ in size, these common principles are unlimited in their aggregation: one (...) very large burden can be outweighed not merely by a large number of middling burdens, but also by a sufficiently large number of very minor burdens. While priority for the significantly more severely burdened when group sizes are equal is uncontroversial, many thinkers have challenged unlimited aggregation. There is, however, little evidence on the public’s views. Here, we examine the responses to priority-setting dilemmas of a representative sample of the UK population (n = 389). We find that an overwhelming majority of respondents’ views do not align with commonly used priority setting principles. A substantial share (forty-four per cent) of respondents do not always prioritize by severity when group sizes are equal. Moreover, among those who do prioritize by severity, most reject unlimited aggregation. A test for the influence of the assumed status quo did not yield a robust effect. Overall, our findings suggest that public support for commonly employed priority-setting principles cannot be assumed, and that unorthodox principles that place limits on the ability of very small burdens to outweigh very large ones may be more popular. (shrink)

If a potential person would have a good life if he were to come into existence, can we coherently regard his coming into existence as better for him than his never coming into existence? And can we regard the situation in which he never comes into existence as worse for him? In this paper, we argue that both questions should be answered affirmatively. We also explain where prominent arguments to differing conclusions go wrong. Finally, we explore the relevance of our (...) answers to issues in population ethics. (shrink)

In 'Why It Matters that Some Are Worse off than Others,' we offer a new critique of the Priority View. In a recent article, Roger Crisp has argued that our critique is flawed. In this reply, we show that Crisp fails to grapple with, much less defeat, the central claim of our critique. We also show that an example that Crisp offers in support of the Priority View in fact lends support to our critique of that view.

Epicurus argued that the good life is the pleasurable life. He also argued that ‘death is nothing to us’. These claims appear in tension. For if pleasure is good, then it seems that death is bad when it deprives us of deeply enjoyable time alive. Here, I offer an Epicurean view of pleasure and the complete life which dissolves this tension. This view is, I contend, more appealing than critics of Epicureanism have allowed, in part because it assigns higher value (...) to pleasures that we produce by exercising our rational capacities and by establishing control over our lives. (shrink)

As health policy-makers around the world seek to make progress towards universal health coverage, they must navigate between two important ethical imperatives: to set national spending priorities fairly and efficiently; and to safeguard the right to health. These imperatives can conflict, leading some to conclude that rights-based approaches present a disruptive influence on health policy, hindering states’ efforts to set priorities fairly and efficiently. Here, we challenge this perception. We argue first that these points of tension stem largely from inadequate (...) interpretations of the aims of priority setting as well as the right to health. We then discuss various ways in which the right to health complements traditional concerns of priority setting and vice versa. Finally, we set out a three-step process by which policy-makers may navigate the ethical and legal considerations at play. (shrink)

I argue that Scanlon's Value of Choice View does not offer a plausible account of substantive responsibility. I offer a new account, which I call the Potential Value of Opportunities View. On this view, when a person is in a position to freely and capably make an informed choice, we assess her situation not by the outcome she achieves but by the potential value of her opportunities. This value depends on the value of the various things that she can achieve (...) through her choices, as well as on how disposed she is to choose her better options and avoid her worse options. This view explains the priority we give to preventing harm that a person cannot avoid by choosing appropriately over harm that a person can so avoid by the fact that the second person has a valuable opportunity that the first does not have. It explains the importance of protecting people against choosing badly by the value of being placed in circumstances in which one is disposed to choose well, and the disvalue of being exposed to the danger of coming to harm by choosing badly. (shrink)

When do claims to be saved of a small or moderate harm aggregate against a competing claim to be saved from an early death? In this short response to Kamm's Bioethical Prescriptions, I argue for the following answer: aggregation of weaker claims against a life is permitted just in case, in a one-to-one contest, a person with a weaker claim would have a personal prerogative to prioritize her claim over a stranger’s competing claim to life.

We reply to critics of the World Health Organisation's Report "Making Fair Choices on the Path to Universal Health Coverage". We clarify and defend the report's key moral commitments. We also explain its role in guiding policy in the face of both financial and political constraints on making fair choices.

This paper introduces a symposium on Equality versus Priority. It explains how cases involving risk are key to distinguishing these views and discusses a 'social egalitarian' critique of both 'telic egalitarians' and 'telic prioritarians'.

When people must either save a greater number of people from a smaller harm or a smaller number from a greater harm, do their choices reflect a reasonable moral outlook? We pursue this question with the help of an experiment. In our experiment, two-fifths of subjects employ a similarity heuristic. When alternatives appear dissimilar in terms of the number saved but similar in terms of the magnitude of harm prevented, this heuristic mandates saving the greater number. In our experiment, this (...) leads to choices that are inconsistent with all standard theories of justice. We argue that this demonstrates the untrustworthiness of distributive judgments in cases that elicit similarity-based choice. (shrink)

In this extended book review, I summarize Adler's views and critically analyze his key arguments on the measurement of well-being and the foundations of prioritarianism.

Epicurus posited that the best life involves the greatest pleasures. He also argued that it involves attaining tranquillity. Many commentators have expressed scepticism that these two claims are compatible. For, they argue, Epicurus’ tranquil life is so austere that it is hard to see how it could be maximally pleasurable. Here, I offer an Epicurean account of the pleasures of tranquillity. I also consider different ways of valuing lives from a hedonistic point of view. Benthamite hedonists value lives by the (...) sum of pleasures minus the sum of pains, weighted by intensity and duration. Meanwhile, Binmore proposes that Epicurus valued lives by their worst episode. In contrast, I offer an Epicurean argument for why the best life is one in which a person attains tranquillity and tastes its pleasures until death. (shrink)

In October 2021, the Inclusive Framework of the Organisation for Economic Co-operation and Development (OECD) adopted a new international tax deal, which has been hailed as a major step towards a fair and effective global corporate tax system. In this article, we question this verdict. We analyse this deal on the basis of three complementary fairness principles: preventing free riding by multinational corporations (MNCs), respect for and promotion of the fiscal autonomy of countries, and the limitation of distributive and relational (...) inequalities. We argue that the tax deal is unlikely to lead to a substantial improvement in fairness. We do, however, welcome the deal’s recognition of the need to tax multinational corporations as unitary entities subject to a global minimum effective tax rate. We argue that this recognition creates opportunities for fairer reforms that should be pursued through a more inclusive global decision-making process. (shrink)

I critically examine a common liberal egalitarian view about the justification for, and proper content of, mandatory health insurance. This view holds that a mandate is justified because it is the best way to ensure that those in poor health gain health insurance on equitable terms. It also holds that a government should mandate what a representative prudent individual would purchase for themselves if they were placed in fair conditions of choice. I argue that this common justification for a mandate (...) is incomplete. A further reason for mandated insurance is that it helps secure social egalitarian public goods that would be underprovided if insurance were optional. I also argue that rather than mandating what a representative individual would choose for themselves, we should design the mandatory package by appealing to a pluralistic egalitarian view, which cares about improving people’s well-being, reducing unfair inequality, and maintaining egalitarian social relations. (shrink)

Common principles for resource allocation in health care can prioritize the alleviation of small health burdens over lifesaving treatment. I argue that there is some evidence that these principles are at odds with a sizable share of public opinion, which holds that saving a life should take priority over any number of cures for minor ailments. I propose two possible explanations for this opinion, one debunking and one vindicatory. I also outline how well-designed surveys and moral inquiry could help decide (...) between them. Finally, I consider how priority-setting principles could be adjusted if the view that saving a life always trumps alleviating small burdens were vindicated. (shrink)

The goal of achieving Universal Health Coverage (UHC) can generally be realized only in stages. Moreover, resource, capacity and political constraints mean governments often face difficult trade-offs on the path to UHC. In a 2014 report, Making fair choices on the path to UHC, the WHO Consultative Group on Equity and Universal Health Coverage articulated principles for making such trade-offs in an equitable manner. We present three case studies which illustrate how these principles can guide practical decision-making. These case studies (...) show how progressive realization of the right to health can be effectively guided by priority-setting principles, including generating the greatest total health gain, priority for the worse off, and financial risk protection. They also demonstrate the value of a fair and accountable process of priority setting. (shrink)

Social Networking Services provide services in return for rights to commercialize users’ personal data. We argue that what makes this transaction permissible is not users’ autonomous consent but the provision of sufficiently valuable opportunities to exchange data for services. We argue that the value of these opportunities should be assessed for both (a) a range of users with different decision-making abilities and (b) third parties. We conclude that regulation should shift from aiming to ensure autonomous consent towards ensuring that users (...) face options that they will use to advance individual and common interests. (shrink)

Can a preference-based conception of welfare accommodate changes in people's preferences? I argue that the fact that people care about which preferences they have, and the fact that people can change their preferences about which preferences it is good for them to have, together undermine the case for accepting a preference-satisfaction conception of welfare.

An conversation with Harry Frankfurt about his views on love, free will, and responsibility, as well as his general approach to philosophy. (Note: a revised version appears in Alex Voorhoeve, Conversations on Ethics, OUP 2009).

The COVID-19 crisis has forced a difficult trade-off between limiting the health impacts of the virus and maintaining economic activity. Welfare economics offers tools to conceptualize this trade-off so that policy-makers and the public can see clearly what is at stake. We review four such tools: the Value of Statistical Life (VSL); the Value of Statistical Life Years (VSLYs); Quality-Adjusted Life-Years (QALYs); and social welfare analysis, and argue that the latter are superior. We also discuss how to choose policies that (...) differentially affect people’s wellbeing. We argue in favor of evaluating policies using a Social Welfare Function (SWF), which evaluates the possible distributions of wellbeing across individuals that may result from a policy. Such a function, we argue, should regard increases in the wellbeing of the less well-off as especially valuable. We then use a model to illustrate how such a framework can help evaluate two broad policy types in response to the pandemic: eradication of the virus, and more lenient control of the spread. Our model reveals how such evaluations depend on many empirical facts but also on key value judgments about the relative importance of health and on the extent of special concern for the worse off. The purpose of this brief is not to make precise recommendations, as conditions vary widely across countries and over time, but to provide a methodology. (shrink)

We analyse three moral dilemmas involving resource allocation in care for HIV-positive patients. Ole Norheim and Kjell Arne Johansson have argued that these cases reveal a tension between egalitarian concerns and concerns for better population health. We argue, by contrast, that these cases reveal a tension between, on the one hand, a concern for equal *chances*, and, on the other hand, both a concern for better health and an egalitarian concern for equal *outcomes*. We conclude that, in these cases, there (...) is much less tension than Norheim and Johansson claim between egalitarian concerns and concerns for better population health. (shrink)

This chapter analyses the behavioural economist Matthew Rabin's work on biases in decision-making. Rabin argues that these biases cause self-harm and that we should tax individuals to ensure that they do not give in to these biases. The chapter's core question is whether there is a soft-paternalistic justification for these taxes. The answer is nuanced. It argues that Rabin’s description of these biases as “irrational” is not always appropriate—sometimes, for example, they are merely a form of preference change. When they (...) are due to the latter, the behaviour is fully voluntary, and there exists no soft-paternalistic justification for coercive intervention. It also argues that even when these biases do lead to substantially non-voluntary choices, we should prefer policies that improve self-knowledge and self-control to taxes. However, the paper notes that Rabin’s analysis reveals circumstances under which these autonomy-enhancing strategies will not be effective. In such cases, and only in such cases, Rabin’s taxes have a soft paternalistic justification. (shrink)

Can we ever truly answer the question, “Who am I?” Moderated by Alex Voorhoeve (London School of Economics), neuro-philosopher Elie During (University of Paris, Ouest Nanterre), cognitive scientist David Jopling (York University, Canada), social psychologist Timothy Wilson (University of Virginia),and ethicist Frances Kamm (Harvard University) examine the difficulty of achieving genuine self-knowledge and how the pursuit of self-knowledge plays a role in shaping the self.

La cobertura universal de salud está en el centro de la acción actual para fortalecer los sistemas de salud y mejorar el nivel y la distribución de la salud y los servicios de salud. Este documento es el informe fi nal del Grupo Consultivo de la OMS sobre la Equidad y Cobertura Universal de Salud. Aquí se abordan los temas clave de la justicia (fairness) y la equidad que surgen en el camino hacia la cobertura universal de salud. Por lo (...) tanto, el informe es pertinente para cada agente que infl uye en ese camino y en particular para los gobiernos, ya que se encargan de supervisar y guiar el progreso hacia la cobertura universal de salud. (shrink)

A short sketch of Erasmus' life and principal ideas.

An interview with Philippa Foot about her book 'Natural Goodness' and the development of her thought. (Note: A slightly revised version appears in Conversations on Ethics, OUP 2009).