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"The Weight of Forever": Peter Wolfendale reviews What We Owe the Future by William MacAskill

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When confronted with a best-selling book by an up-and-coming Oxford philosopher, it’s hard to resist the urge to subject the title to a little linguistic analysis. Building on the success of his previous book, Doing Good Better, which introduced the wider public to the idea of effective altruism – optimising our positive impact on the world through scientific philanthropy – William MacAskill’s new book What We Owe the Future introduces us to the idea of longtermism, which extends the scope of such optimisation to cover our impact upon the far-flung future. But, giving in to our inner pedants, we might be inclined to ask: is “the future” the sort of thing to which one can “owe” anything? We generally take ourselves to have obligations to people, mostly others and sometimes even ourselves. We aren’t typically indebted to things, be they inanimate objects or (vast) stretches of time. I’m not sure I owe the 21st century anything, literally speaking, let alone the long aeons that follow.

It’s thus perhaps unsurprising that the book begins by inviting us to personify the future: we are to imagine that we are everyone who has, does, or will exist, living each life out in order, from prehistory until the end of time; and from our vantage in the present consider the quality of those lives still to come, the fate of humanity in aggregate now singular destiny. From this perspective, the overwhelming majority of our life lies before us, and the choices we make now will determine just how good the rest of it will be. What we owe to the future is thereby framed as if it were an obligation to ourselves. Sheer self-interest would dictate that we get our act together, get our priorities straight, and cultivate the capacity for (extremely) delayed gratification. Of course, this is only an allegory, not an argument, but it shades into one of MacAskill’s guiding metaphors: “humanity as an imprudent teenager” reaching the age at which it needs to decide what it’s going to do with itself – getting an eduction, choosing a career, and perhaps settling down in a nice galactic supercluster to raise a few quadrillion kids as extensions of itself. But that’s skipping ahead to the end. For now, let’s return to the beginning, bearing the problem of obligation in mind.

In essence, the book sets out to do two things: to lay out the philosophical framework that motivates longtermism (principally chapters 1, 2, 8, and 9), and to sketch the political program this framework implies when combined with empirical research into the current state of the world and its likely future trajectories (chapters 3 to 7, and 10). MacAskill’s prose is light and easy to follow. Technical vocabulary is kept to a minimum, and is always explained when introduced, with judicious use of concrete examples. There are however a lot of numbers, ranging from complex meta-analyses of social trends with accompanying charts and graphs (e.g., standard of living changes in the US: 1870-2020) to fantastical figures that seem more like convenient back of the envelope calculations (e.g., the moral significance of terrestrial species ranked by aggregate mass of neurons). It’s perhaps easier to feel lost in these sections, though their workings are available to be checked, alongside the other domain-specific research carried out by the team of experts that helped MacAskill compose the book. What ties this all together is a touch of historical narrative. The more empirically-minded chapters begin by taking paradigm cases from the past that illustrate the point in question: ranging from the Chinese Warring States period (the persistence of value changes), through the Islamic Golden Age (the cost of societal stagnation), to the birth of the Abolitionist movement (small groups can effect big changes), and the creation of the Spaceguard defence program (the tractability of x-risks). These episodes set the rhetorical pace of the book, conjuring a sense that the shape of future events is equally legible.

In what follows I’m going to bypass such narratives. Instead, I’ll try to reconstruct the overall argument of the book in as much detail as is reasonable, before turning to the task of assessing it. In the first two sections, I’ll outline the philosophical framework and its corresponding political program. In the third and fourth sections, I’ll summarise the most coherent common objections to the positions these incorporate, and then propose a more original criticism of the overall perspective of longtermism. Finally, I’ll conclude by returning to the opening metaphors.


The Longtermist Framework

The philosophical framework of longtermism rests on two seemingly innocuous propositions: that future people count, and that numbers matter. The first claim is that whatever moral concerns apply to people alive in the present should also apply to those who do not yet exist, and that this holds no matter how far into the future they might be. MacAskill motivates this in two ways. On the one hand, he appeals to our intuitions about the moral significance of harm: if we leave broken glass on a mountain trail and this results in a little girl being hurt, we are culpable regardless of whether this injury occurs the next day or in the next century. On the other, he suggests that distance in time is morally equivalent to distance in space: our prima facie obligations to those who live in distant times are more or less the same as our obligations to those who live in distant lands. The second point is that, when weighing competing claims that such obligations make upon us, we often have to turn to numbers (e.g., selecting the course of action that will harm the fewest people), and that whatever moral calculus we choose to apply in these cases must include the claims of the unborn (e.g., selecting an action that may harm some people in the present if it spares more people in the future). MacAskill is willing to countenance that future claims may be discounted relative to present ones for a few reasons, but these discounts are ultimately irrelevant. This is because the number of people who may follow in our footsteps is so vast as to verge on the sublime. MacAskill illustrates this, literally, by filling a few pages with icons representing a billion people each, and explaining that 20,000 pages would be required simply to cover the projected population of earth over the next 500 million years. Even with steep per capita discounts, this leaves a large range of cases in which the claims of the future easily outweigh those of the present. It’s precisely these cases with which longtermism is concerned.

The immediate problem posed by all this is how to perform the relevant moral accounting, and for this task MacAskill turns to decision theory: a formal approach to making choices that works by ascribing quantities of value to their intended outcomes, such that the options can be ranked. More specifically, he advocates making choices based on expected value: the product of an outcome’s potential value and the probability of it coming to pass. This inclines us to aim for worse outcomes that are significantly more likely than the better alternatives (e.g., amputating a limb, rather than hoping an infection won’t spread), and unlikely outcomes that are significantly better than the likelier ones (e.g., buying a lottery ticket, rather than a third packet of crisps). Finally, he breaks down the value of every outcome into three components: significance, persistence, and contingency. Significance is simply whatever is good about the outcome (e.g., providing shelter to a homeless person), persistence is how long this good persists (e.g., is the shelter temporary or permanent?), and contingency is roughly how rare this good is, or how unlikely it would be to occur if we don’t choose to realise it right now (e.g., would someone else provide it if we don’t?). Each factor is weighted by expectation separately before they are summed together. This is the abstract framework that MacAskill applies to the concrete political problems posed in the middle of the book.

You may have noticed that what was originally framed in terms of obligations to act in certain ways (i.e., the rights of future people not to be harmed) has somehow become a matter of the relative worth of states of affairs (i.e., whether a world in which future people’s lives are improved is better, overall). To put this in more technical terms, we seem to have slipped from deontology into axiology. These are to some extent interchangeable: to say that one painting is better than another appears to imply that, all else being equal, if you can only save one from the flames, you ought to choose the former; and it seems natural to say that when you’re obliged to sacrifice one life for the sake of ten, this implies that this is more important than the alternative. However, this only works up to a point. Some conflicting obligations invite obvious quantitative comparisons (e.g. saving more or fewer lives), but others don’t (e.g., breaking a promise or preventing a harm). There are equally different types of value (e.g., beauty, justice, or utility), which motivate different sorts of actions (e.g., appreciation, coercion, or acquisition), and permit extensive and fine-grained comparisons between states/acts without thereby being mutually comparable. It would theoretically be possible for MacAskill to wield decision theory on a case-by-case basis, making use of local metrics that rank certain types of state or event without committing himself to a global metric that makes every outcome comparable, but this is clearly not what he intends. He wants to consider the future as a whole, in order to chart the best possible path through it, and this means embracing some measure of absolute value, or goodness simpliciter. Precisely what this measure might be is not addressed in the more concrete sections of the book (chapters 3-7), where a combination of liberal values (egalitarianism and econometrics) play proxy for it, but it eventually comes out into the open (chapters 8 and 9), just in time to motivate the book’s most controversial claims.

MacAskill wants to consider the future as a whole, in order to chart the best possible path through it, and this means embracing some measure of absolute value, or goodness simpliciter.

I am of course speaking of well-being. This is one of those philosophical concepts we seem to have an intuitive grasp of: we’re more or less happy talking about more or less happy lives. But shaping these intuitions into a coherent and precise measure of absolute value is a tricky matter. MacAskill mentions the three main approaches – preference satisfaction (getting what we want), hedonism (getting what we enjoy), and objective lists (getting what is good for us) – but stays agnostic as to which is correct. The only constraints he imposes on well-being are that it is quantifiable, and that it can be negative as well as positive: there may be some lives which are not worth living. However, this doesn’t mean he says nothing about how we might measure well-being. A significant chunk of chapter 9 is devoted to various methods of measurement, all in the name of establishing whether the world is currently in a state of net-positive well-being (it is), and so whether or not we should aim to preserve the core features of our current way of life (we should). This is also where the narrow focus on human well-being gets widened to encompass the lives of animals, with some surprising conclusions: human use of domesticated livestock is an unmistakable negative for well-being, but human eradication of natural animal populations is probably a net-positive, given how miserable their lives must be on average. MacAskill elsewhere considers the possible contributions of aliens, our extinct hominin relatives, and the post-human progeny we may someday give rise to. But beyond these calculations, the key philosophical claim is that whatever else we may take to be valuable in some way (e.g., art, nature, knowledge, or liberty) is only valuable as a means to the end of well-being, whatever it consists in.

The really controversial claims, however, are made in chapter 8, which discusses the field of population ethics: whether, why, and when it is right to bring new people – new bearers of well-being – into the world. Here MacAskill sets out to establish that “all other things being equal, having more happy people makes the world a better place.” (169). He opens by claiming that every consistent position currently defended in the field entails counter-intuitive and potentially unpalatable conclusions, but we must nevertheless choose between them. The first option is the average view: we should raise the average well-being of the population. The downside of this is that it might encourage us to create a lot of people in outright suffering, as long as they suffer less than the current average. The second is the total view: we should raise the overall well-being of the population. The downside of this is what Derek Parfit called the repugnant conclusion: that it might encourage us to create an arbitrarily large number of people with marginally positive well-being rather than any smaller number of people living genuinely good lives. The final option is the critical level view: we should ensure that the well-being of the population’s members exceeds whatever threshold passes for a good life. The downside of this is the sadistic conclusion: that it might encourage us to create a few people in abject misery rather than a larger number of people who live lives just shy of good.

It’s important to see that each of these options depends upon a peculiar moral symmetry, captured in the following inference: if making new people with unhappy lives is bad (obvious), then making new people with happy lives must be good (contentious). It seems that the best way to avoid the unpalatable choice between the above options would thus be to argue that these situations are really asymmetrical: it can be bad to create a miserable person and yet be neither better nor worse to make a happy person than no person at all. MacAskill calls this the “the intuition of neutrality”, and presents two distinct arguments against it. His first argument proceeds from the fragility of identity, or the fact that slight changes to the context of conception result in entirely distinct people being born. Because any long-term intervention will affect these contexts, neutrality would imply that all such interventions are equally worthwhile. To put this in more concrete terms, if we enact a climate change action plan to make the future better for those who follow us, the people who will exist in the future will be distinct from the people who would have existed otherwise, and so it could not strictly be better. To retain long-term moral distinctions, we must reject neutrality. His second argument goes as follows: say a couple are considering having a child, but the mother has a vitamin deficiency that will result in a child who suffers from migraines if conceived before taking supplements. They thus have three options: a) no child, b) a child with migraines now, or c) a child without migraines later. Neutrality implies that options (b) and (c) are both as good as option (a), but that in turn implies that they should be equally as good as one another. This contradicts the obvious moral imperative to choose (c) over (b), all else being equal. So again, neutrality must be rejected. If you’re suspicious of these arguments, I think you’re right to be, but I’ll hold off any criticisms for now.

Out of all the available options, MacAskill accepts the total view, repugnant conclusion and all. But that’s only the beginning of the controversy. There would appear to be two major consequences of his positions: in the short-term, that we should have kids; and in the long-term, that we should colonise space. There’s reason to be fruitful and multiply at whatever scale we can manage. The grandest possible scale puts those putative 20,000 pages to shame. We would need massive libraries packed with nothing but weighty tomes just to illustrate the extent to which the moral claims of a future space fairing civilisation outweigh the meagre concerns of the present. However, these two cases are treated somewhat differently. On the one hand, MacAskill doesn’t claim that “we are morally required to bring more happy people into existence, or that we’re blameworthy if we fail to do so – just that, all other things being equal, having more people makes the world a better place” (169). Yet, on the other, he does think that “the practical upshot of this is a moral case for space settlement” (189). What exactly is going on here?

When it comes to the political domain, longtermism takes a more aggressive approach to its conflicts with common sense.

Well, MacAskill seems to be proposing a compromise of sorts between the deontic and the axiological. This is not the only instance of such compromise. Throughout the book he is at pains to insist that longtermism is compatible with dominant liberal values, and that it can’t be used to make cases for violating individual rights, including our right not procreate should we choose. This sometimes comes across as a mere rhetorical compromise, designed to placate the worries of potential sceptics, but there are at least two arguments offered for it. The first isn’t articulated in a single place, but is more of a thread that runs throughout the book. It suggests that liberty is instrumentally important from a consequentialist perspective, both as a component of personal well-being and as a structural feature of societies that optimise for it in the long-term. The second is articulated, and draws on MacAskill’s extant work on moral uncertainty (see, for example, his 2020 book, Moral Uncertainty, co-authored with Krister Bykvist and Toby Ord). It suggests that if we are not completely certain that consequentialism is true, and thus that there is some significant chance that liberty is an intrinsic good, then we should aim to act in ways that are as consistent with this as possible. It is on this basis that he can write: “I see longtermism as a supplement to commonsense morality, not a replacement for it” (241). However, when it comes to the political domain, longtermism takes a more aggressive approach to its conflicts with common sense.


The Longtermist Programme

The political programme of longtermism is founded upon a singular speculative thesis: that we are currently at a crux point in history, where our actions may have an outsized influence upon the shape of everything that comes after. We’re in the middle of a period of rapid social and technological change, yet at the same time we’re more interconnected as a species than we’ve ever been before. MacAskill argues that this means our society is in a state like molten glass: easily shaped into new configurations that once they settle might persist for an extremely long time, influencing the lives of untold trillions across a vast swathe of space. We thus have a responsibility to ensure that it ends up in the right configuration, which first and foremost means avoiding the wrong ones. The worst outcome would be our complete extinction. This would not only eliminate whatever good we currently bring to the world, but would foreclose the possibility of those far greater goods of which we’re capable. Once we account for this loss of potential, extinction events are so much worse than even near-extinction events that tiny probabilities demand decisive action to mitigate against them. MacAskill admits that there might technically be even worse states than extinction, such as societies designed to perpetuate endless torture, but he thinks that these are vanishingly unlikely, because they require unsustainably malign intent.

The next worst outcome would be societal collapse. MacAskill defines that as the loss of the capacity to produce industrial and post-industrial technology. This is a fall from grace we might come back from, but we might equally never recover, or slip still further into extinction. The good news is that, according to MacAskill’s experts, civilisation is a good deal more resilient than you might expect: even under very grim assumptions about mass death and resource depletion, agriculture and industrialisation are likely to re-occur in the short- to medium-term. He is even quite upbeat about catastrophic climate change: “even with 15 degrees of warming, the heat would not pass the lethal limit for crops in most regions” (137). The main danger there is unforeseen tipping points (e.g., collapse of cloud formation) that commit us to unsurvivable warming once a certain threshold is passed. The main risk to the rebirth of technological civilisation turns out to be lack of fossil fuels. If we burn through them before society collapses, there may not be enough left to bootstrap a new industrial base. The longtermist prescription is thus that we must not only stop burning them to prevent climate change, but also to give ourselves a second chance should society ever collapse.

Beyond this, there is societal stagnation. MacAskill analyses this principally in economic terms, focusing on economic growth as a metric of progress, and identifying technological development as the key factor driving growth. Stagnation is inherently bad, insofar as it represents lost potential, though in the cosmic scheme of things this may be little more than a blip on the path to interstellar civilisation. However, there are graver risks associated with it. A given technological level is not always sustainable in the long run (e.g., fossil fuel-based industry), and so stagnation eventually risks regression, which might then lead to collapse and even extinction. MacAskill notes that technological progress has been slowing since the 1970s, with few major innovations outside of IT and telecommunications. His hypothesis for explaining this downturn is that we are gradually exhausting the low-hanging fruit of available technological discovery, and that, even given ways of making that process more efficient, it is in the end a numbers game: specifically, population size, as this determines how many people can be dedicated to research and development.[1] The upshot of this analysis is that the greatest potential driver of stagnation is population decline, which is another trend we can forecast given the drop in rates of reproduction across the board in developed countries. This means that there are also instrumental reasons to encourage procreation on a large scale (at least until discovery can be automated). A final, less obvious danger of stagnation is that in the name of reversing it, society may change its values for the worse (e.g., normalising exploitation or slavery).

The risks and rewards of value change is another key topic for MacAskill. As already suggested, he’s broadly in favour of the liberal values dominant in most Western democracies, by which I mean some mix of deontic and axiological principles that favour a balance between social egalitarianism and individual liberty putatively compatible with a market economy under capitalism. He thinks there’s room for improvement here (e.g., on animal rights) and is willing to countenance uncertainty about where improvements must be made, but he believes that the last two centuries have seen definite moral progress (e.g., abolitionism and feminism). Although he insists that this progress wasn’t guaranteed by any means, he does suggest that it wasn’t entirely accidental: technological progress tends to enable moral progress, as the ensuing economic growth encourages egalitarian attitudes, and the critical mindset required by science spills over into ethics. The pressing problem is how to ensure such moral progress continues, and to prevent premature lock-in to a poor set of values. Here his prescriptions are recognisably liberal: to encourage open political experimentation by structuring relationships between diverse communities in ways that sustain competitive evolution (e.g., charter cities), while emphasising the importance of free speech and free migration. The main problem for this is equally recognisable: a variant of the paradox of tolerance regarding which values must be locked-in now to prevent premature lock-in of others.

Beyond climate change, MacAskill considers three concrete dangers that come with significant risk of collapse or extinction. From least to most severe, these are: world wars, engineered pandemics, and the emergence of artificial general intelligence (AGI). His reasons for ranking engineered pandemics more highly than world wars are persuasive and thoroughly researched. While I can’t really do justice to them here, it’s worth pointing out that MacAskill has form on this issue: he’s been campaigning for increased pandemic preparedness since before the outbreak of COVID-19. However, his reasons for ranking the threat posed by AGI above war, plague, and climate change are less squarely empirical and at least as controversial as his claims about population ethics. Those who have read Superintelligence, a 2014 book by MacAskill’s Oxford colleague and long-standing longtermist Nick Bostrom, will be familiar with the basic idea: the potential for AGI to recursively improve itself will create a truly epochal break, as it quickly becomes powerful enough to obviate human agency entirely. According to MacAskill, the issue is not just the power of AGIs but their constancy: they are effectively immortal and unchanging, so that whichever priorities they begin with – be they our own values, some disastrous approximation thereof, or a spontaneous drive to dominate or destroy us – these are likely to be locked-in forever, our molten destiny flash-freezing into crystalline fate. Figuring out how to ensure AGI is aligned with the correct values is thus not only avoiding a possible extinction risk (the likelihood of which varies wildly with expert opinion), but actively steering the future towards desirable outcomes. This also makes it even more important to cultivate and propagate good values before AGI arrives.

AGIs are effectively immortal and unchanging, so that whichever priorities they begin with, these are likely to be locked-in forever, our molten destiny flash-freezing into crystalline fate.

MacAskill acknowledges that these risk assessments are provisional. In the face of uncertainty about the future, he advocates three rules of thumb: 1) take actions we’re confident are good, 2) maximise our available options, and 3) learn more. The first rule recommends immediate action on climate change, fossil fuel depletion, and pandemic preparedness. The other two recommend a more circumspect approach to AGI and world war. The book closes by considering how we should go about implementing these priorities. At the individual level, MacAskill counsels against focusing exclusively on improving our own behaviour (e.g., engaging in more ethical patterns of consumption). Instead, he recommends three specific things: political activism, ideological evangelism, and having children. At the collective level, he calls for people to work together in groups, establishing an effective division of labour, and ultimately building a wider movement. In many ways this is a natural extension or evolution of the effective altruism movement that he’s been cultivating for the past decade. Nevertheless, there is another compromise here. MacAskill stipulates that the book only makes a case for what he calls weak as opposed to strong longtermism, in which optimising the goodness of the far-flung future is merely one among our most pressing priorities, rather than the most pressing one. This weaker position is perhaps more conducive to the task of movement-building, as it is less likely to alienate potential allies and recruits, but it’s worth noting that he explicitly defends the stronger position elsewhere (see his 2021 working paper, “The Case for Strong Longtermism”, co-written with Hilary Greaves). It’s the seeming inevitably of this slide from weak to strong longtermism, and the ensuing abandonment of his other moral compromises, which most alarms MacAskill’s critics.

The Flaws of Longtermism

One metric by which we might judge the success of What We Owe the Future is the amount of critical engagement it has drawn, and it has drawn quite a lot. The main worry shared by most critics is that MacAskill’s moral accountancy might be used – counter to his stated intent – to rationalise taking questionable risks in the present for intangible rewards in the very far future, e.g., redirecting funding from climate change mitigation to speculative AI safety research, or abandoning attempts to save lives in the third-world because on average lives in the first-world contribute