Hilary Greaves

To discount future benefits and costs is to assign them less weight in one’s cost-effectiveness calculations than one assigns to immediate benefits and costs. When the benefits and costs are monetary ones, there is a widespread and theoretically well-grounded consensus that discounting is appropriate. The case of discounting future health is more controversial, and many authors have argued for a zero discount rate for health. Here the author argues that while the usual arguments for discounting money do not apply to health, there are two other good reasons (related, respectively, to uncertainty and to instrumental effects) for discounting health within the simple models that form the basis of much cost-effectiveness analysis. Both of these reasons, however, would be inapplicable in more detailed models that represented uncertainties and instrumental effects explicitly.

The standard case for longtermism focuses on a small set of risks to the far future, and argues that in a small set of choice situations, the present marginal value of mitigating those risks is very great. But many longtermists are attracted to, and many critics of longtermism worried by, a farther-reaching form of longtermism. According to this farther-reaching form, there are many ways of improving the far future, which determine the value of our options in all or nearly all choice situations, and will continue to do so over the coming decades even if we make substantial investments in longtermist priorities. This chapter highlights the gap between the minimal form of longtermism established by standard arguments and this more expansive view, and considers (without reaching any firm conclusions) which form of longtermism is more plausible.

True benevolence is, most fundamentally, a desire that the world be better. It is natural and common, however, to frame thinking about benevolence indirectly, in terms of a desire to make a difference to how good the world is. This would be an innocuous shift if desires to make a difference were extensionally equivalent to desires that the world be better. This paper shows that at least on some common ways of making a “desire to make a difference” precise, this extensional equivalence fails. Where it fails, “difference-making preferences” run counter to the ideals of benevolence. In particular, in the context of decision making under uncertainty, coupling a “difference-making” framing in a natural way with risk aversion leads to preferences that violate stochastic dominance, and that lead to a strong form of collective defeat, from the point of view of betterness. Difference-making framings and true benevolence are not strictly mutually inconsistent, but agents seeking to implement true benevolence must take care to avoid the various pitfalls that we outline.

True benevolence is, most fundamentally, a desire that the world be better. It is natural and common, however, to frame thinking about benevolence indirectly, in terms of a desire to make a difference to how good the world is. This would be an innocuous shift if desires to make a difference were extensionally equivalent to desires that the world be better. This paper shows that at least on some common ways of making a “desire to make a difference” precise, this extensional equivalence fails. Where it fails, “difference-making preferences” run counter to the ideals of benevolence. In particular, in the context of decision making under uncertainty, coupling a “difference-making” framing in a natural way with risk aversion leads to preferences that violate stochastic dominance, and that lead to a strong form of collective defeat, from the point of view of betterness. Difference-making framings and true benevolence are not strictly mutually inconsistent, but agents seeking to implement true benevolence must take care to avoid the various pitfalls that we outline. GPI Working Paper No. 16-2022

This chapter makes the case for strong longtermism: the claim that, in many situations, impact on the long-run future is the most important feature of our actions. Our case begins with the observation that an astronomical number of people could exist in the aeons to come. Even on conservative estimates, the expected future population is enormous. We then add a moral claim: all the consequences of our actions matter. In particular, the moral importance of what happens does not depend on when it happens. That pushes us toward strong longtermism. We then address a few potential concerns, the first of which is that it is impossible to have any sufficiently predictable influence on the course of the long-run future. We argue that this is not true. Some actions can reasonably be expected to improve humanity’s long-term prospects. These include reducing the risk of human extinction, preventing climate change, guiding the development of artificial intelligence, and investing funds for later use. We end by arguing that these actions are more than just extremely effective ways to do good. Since the benefits of longtermist efforts are large and the personal costs are comparatively small, we are morally required to take up these efforts.

Recent years have seen a flurry of interest in longtermism: roughly, the view that positively influencing the long-term future is a key moral priority of our time. Familiar calls to take a long-term view towards global problems such as climate change and poverty typically urge us to plan on a scale of decades or perhaps a century. By contrast, longtermism asks us to take seriously the idea that what we should do right now may depend on the effects of our actions thousands or even millions of years hence. This volume brings together leading scholars to discuss four sets of overlapping questions raised by longtermism. First, should we accept some version of longtermism? Second, to what extent can we predict and control the far future? Third, which ethical priorities are recommended by longtermism, and how revisionary are they? Finally, what implications would longtermism have for the design or reform of social, political, and legal institutions? Contributors include both supporters and critics of longtermism, and are drawn from a range of disciplines including philosophy, economics, psychology, law, political science, and mathematics, and from private industry.

Much of the evidence for quantum mechanics is statistical in nature. The Everett interpretation, if it is to be a candidate for serious consideration, must be capable of doing justice to reasoning on which statistical evidence in which observed relative frequencies that closely match calculated probabilities counts as evidence in favour of a theory from which the probabilities are calculated. Since, on the Everett interpretation, all outcomes with nonzero amplitude are actualized on different branches, it is not obvious that sense can be made of ascribing probabilities to outcomes of experiments, and this poses a prima facie problem for statistical inference. It is incumbent on the Everettian either to make sense of ascribing probabilities to outcomes of experiments in the Everett interpretation, or to find a substitute on which the usual statistical analysis of experimental results continues to count as evidence for quantum mechanics, and, since it is the very evidence for quantum mechanics that is at stake, this must be done in a way that does not presuppose the correctness of Everettian quantum mechanics. This requires an account of theory confirmation that applies to branching-universe theories but does not presuppose the correctness of any such theory. In this paper, we supply and defend such an account. The account has the consequence that statistical evidence can confirm a branching-universe theory such as Everettian quantum mechanics in the same way in which it can confirm a probabilistic theory.

The notion of existential catastrophe is increasingly appealed to in discussion of risk management around emerging technologies, but it is not completely clear what this notion amounts to. Here, I provide an opinionated survey of the space of plausibly useful definitions of existential catastrophe. Inter alia, I discuss: whether to define existential catastrophe in ex post or ex ante terms, whether an ex ante definition should be in terms of loss of expected value or loss of potential, and what kind of probabilities should be involved in any appeal to expected value.

Nick Bostrom and others have suggested treating decision-making under moral uncertainty as analogous to parliamentary decision-making. The core suggestion of this “parliamentary approach” is that the competing moral theories function like delegates to the parliament, and that these delegates then make decisions by some combination of bargaining and voting. There seems some reason to hope that such an approach might avoid standard objections to existing approaches (for example, the “maximise expected choiceworthiness” (MEC) and “my favourite theory” approaches). However, the parliamentary approach is so far extremely underspecified, making it largely indeterminate how such a model will in fact behave in the respects that those concerned with moral uncertainty care about. This paper explores one way of making it precise. We treat predicaments of moral uncertainty as analogous to bargaining situations alone (setting aside voting), and apply a version of the Nash solution that is standard in bargaining theory. The resulting model does indeed perform in many of the hoped-for ways. However, so also does a version of MEC that employs a structural approach to intertheoretic comparisons. It seems to us an open question which, regarding this version of MEC and the bargaining-theoretic approach, is superior to the other. We identify the key points on which the two differ.

Existence comparativism holds that it can sometimes be better or worse, for a given person, that that person exist rather than not. The dominant argument in the literature on this issue is the Metaphysical Argument, which purports to show that existence comparativism is metaphysically incoherent. The argument of this chapter is that the Metaphysical Argument fails. Even if existence cannot be personally better than non-existence, the Metaphysical Argument cannot be the reason for this, since the argument proves too much. Denying its first premise means holding that personal betterness comparisons between a fixed pair of possible worlds are contingent; some recent work has taken this course. Denying the second premise means holding that A can be better for S than B even when S does not exist. This chapter presents the case for denying the second premise. Contrary to something of a consensus in the literature, this is not absurd in general metaphysical terms. And there is a particular analysis of personal betterness comparisons that explains in more detail how one outcome can be better than another for an individual who does not exist. The chapter therefore concludes that existence comparativism, whether true or false, is metaphysically coherent.

This is the first collective study of the thinking behind the effective altruism movement. This movement comprises a growing global community of people who organise significant parts of their lives around the two key concepts represented in its name. Altruism is the idea that if we use a significant portion of the resources in our possession—whether money, time, or talents—with a view to helping others then we can improve the world considerably. When we do put such resources to altruistic use, it is crucial to focus on how much good this or that intervention is reasonably expected to do per unit of resource expended (as a gauge of effectiveness). We can try to rank various possible actions against each other to establish which will do the most good with the resources expended. Thus we could aim to rank various possible kinds of action to alleviate poverty against one another, or against actions aimed at very different types of outcome, focused perhaps on animal welfare or future generations. The scale and organisation of the effective altruism movement encourage careful dialogue on questions that have perhaps long been there, throwing them into new and sharper relief, and giving rise to previously unnoticed questions. In this volume a team of internationally recognised philosophers, economists, and political theorists present refined and in-depth explorations of issues that arise once one takes seriously the twin ideas of altruistic commitment and effectiveness.

Harsanyi claimed that his Aggregation and Impartial Observer Theorems provide a justification for utilitarianism. This claim has been strongly resisted, notably by Sen and Weymark, who argue that while Harsanyi has perhaps shown that overall good is a linear sum of individuals’ von Neumann–Morgenstern utilities, he has done nothing to establish any connection between the notion of von Neumann–Morgenstern utility and that of well-being, and hence that utilitarianism does not follow. The present article defends Harsanyi against the Sen–Weymark critique. I argue that, far from being a term with precise and independent quantitative content whose relationship to von Neumann–Morgenstern utility is then a substantive question, terms such as ‘well-being’ suffer (or suffered) from indeterminacy regarding precisely which quantity they refer to. If so, then (on the issue that this article focuses on) Harsanyi has gone as far towards defending ‘utilitarianism in the original sense’ as could coherently be asked.

This dissertation explores several issues related to the CPT theorem. Chapter 2 explores the meaning of spacetime symmetries in general and time reversal in particular. It is proposed that a third conception of time reversal, 'geometric time reversal', is more appropriate for certain theoretical purposes than the existing 'active' and 'passive' conceptions. It is argued that, in the case of classical electromagnetism, a particular nonstandard time reversal operation is at least as defensible as the standard view. This unorthodox time reversal operation is of interest because it is the classical counterpart of a view according to which the so-called 'CPT theorem' of quantum field theory is better called 'PT theorem'; on this view, a puzzle about how an operation as apparently non-spatio-temporal as charge conjugation can be linked to spacetime symmetries in as intimate a way as a CPT theorem would seem to suggest dissolves. In chapter 3, we turn to the question of whether the CPT theorem is an essentially quantum-theoretic result. We state and prove a classical analogue of the CPT theorem for systems of tensor fields. This classical analogue, however, appears not to extend to systems of spinor fields. The intriguing answer to our question thus appears to be that the CPT theorem for spinors is essentially quantum-theoretic, but that the CPT theorem for tensor fields applies equally to the classical and quantum cases. Chapter4 explores a puzzle that arises when one puts the CPT theorem alongside a standard way of understanding spacetime symmetries, according to which spacetime symmetries are to be understood in terms of background spacetime structure. The puzzle is that a 'PT theorem' amounts to a statement that the theory may not make essential use of a preferred direction of time, and this seems odd. We propose a solution to that puzzle for the case of tensor field theories.

It is often claimed that reducing population size would be advantageous for climate change mitigation, on the grounds that lower population would naturally correspond to lower emissions. This apparently obvious claim is in fact seriously misleading. Reducing population size would indeed, other suitable things being equal, reduce the emissions rate. But it is well recognised that the primary determinant of the eventual amount of climate change is not the emissions rate, but rather cumulative emissions. It is far less clear whether reducing population size would reduce cumulative emissions, or would in any other way prove an advantage for reasons related to climate change. This paper identifies and briefly discusses the issues relevant to assessing that less clear question.

Rights-based approaches and consequentialist approaches to ethics are often seen as being diametrically opposed to one another. In one sense, they are. In another sense, however, they can be reconciled: a ‘global’ form of consequentialism might supply consequentialist foundations for a derivative morality that is non-consequentialist, and perhaps rights-based, in content. By way of case study to illustrate how this might work, I survey what a global consequentialist should think about a recent dispute between Jeff McMahan and Henry Shue on the morality and laws of war.

I argue that excessive reliance on the notion of “the badness of death” tends to lead theorists astray when thinking about healthcare prioritisation. I survey two examples: the confusion surrounding the “time-relative interests account” of the badness of death, and a confusion in the recent literature on cost-benefit analyses for family planning interventions. In both cases, the confusions in question would have been avoided if (instead of attempting to theorise in terms of the badness of death) theorists had forced themselves first to write down an appropriate value function, and then focused on the question of how to maximize value.

According to Bayesian epistemology, the epistemically rational agent updates her beliefs by conditionalization: that is, her posterior subjective probability after taking account of evidence X, pnew, is to be set equal to her prior conditional probability pold(·|X). Bayesians can be challenged to provide a justification for their claim that conditionalization is recommended by rationality—whence the normative force of the injunction to conditionalize? There are several existing justifications for conditionalization, but none directly addresses the idea that conditionalization will be epistemically rational if and only if it can reasonably be expected to lead to epistemically good outcomes. We apply the approach of cognitive decision theory to provide a justification for conditionalization using precisely that idea. We assign epistemic utility functions to epistemically rational agents; an agent’s epistemic utility is to depend both upon the actual state of the world and on the agent’s credence distribution over possible states. We prove that, under independently motivated conditions, conditionalization is the unique updating rule that maximizes expected epistemic utility.