Imagine you’re hiking on a rocky backwoods trail in Yosemite National Park, and you accidentally drop a glass bottle that shatters everywhere. If you knew with certainty that a hiker on the same trail the next day would cut herself on the broken glass, you would surely clean up after yourself, as you would if you knew that the hiker was going to hit the trail the following week.

But what if you knew that the hiker wouldn’t arrive for another year? Or 10 years? Or a thousand years? Would you still feel obliged to clear away the shards? At what point would your moral responsibility to prevent injury to a future hiker begin to wane?

If you ask William MacAskill, the answer is, essentially, never.

McAskill is an Oxford philosopher, a founder of the so-called effective-altruism movement, and the author of the thought-provoking, meticulously researched, but theoretically and practically flawed new book What We Owe the Future. He labels his governing framework “longtermism,” which he defines as “the idea that positively influencing the longterm future is a key moral priority of our time,” the notion of “taking seriously just how big the future could be and how high the stakes are in shaping it.”

Effective altruism emerged in the mid-2000s as something like the philanthropic expression of the extreme utilitarianism of Princeton philosopher Peter Singer. Effective altruists generally eschew “feel good” work in the nonprofit sector in favor of employment in the world of finance coupled with massive charitable contributions. It is far better, they reckon, to save dozens of lives in the developing world with surplus income from a lucrative hedge-fund position than to marginally improve an NGO supplying laptops to the Global South. Like MacAskill himself, many effective altruists practice what they preach, living frugally in large groups in cramped quarters and abjuring even the most basic luxuries in order to give away what they earn.

The movement, criticized by some as overly cold and calculating, has exploded in recent years. According to the New Yorker, EA “controls philanthropic resources on the order of thirty billion dollars,” including, most prominently, the support of Sam Bankman-Fried, the 30-year-old crypto pioneer and wunderkind billionaire. Generously endowed EA-affiliated entities with names like Open Philanthropy, GiveWell, Rethink Priorities, and the Forethought Foundation have sprouted on both sides of the Atlantic. And this year, for the first time, an EA-oriented candidate ran for Congress, placing second in an Oregon Democratic primary.

Lately, EAs have trained their fire on enhancing the distant future. In his book, MacAskill focuses his analysis on four key claims: “that, impartially considered, future people should count for no less, morally, than the present generation; there may be a huge number of future people; that life, for them, could be extraordinarily good or inordinately bad; and that we really can make a difference to the world they inhabit.”

If you assume that humanity will last at least as long as the typical mammalian species, McAskill argues, we’ve still got another 700,000 years remaining before we go the way of the dodo. In that case, we can expect another 80 trillion future people to exist—10,000 times the current global population.

Humanity could, of course, kill itself off within centuries, decades, or even years. MacAskill estimates a 1 percent probability that civilizational collapse—whether as a result of a calamitous nuclear war, a global pandemic caused by engineered pathogens, or catastrophic climate change—could occur within this century. That’s 100 times the risk of an individual dying in a car crash in any given year. And the likelihood of global breakdown increases significantly as we move beyond this century. “If humanity is like a teenager,” he suggests, “then she is one who speeds round blind corners, drunk, without wearing a seat belt.”

But we could also figure out ways to survive much longer. He asserts that Earth will remain habitable for 500 million years, the sun will keep burning for another 5 billion years, and other stars will shine for trillions of years. Thus, whether we’re staving off irreversible disaster or improving conditions for our future selves, the stakes are sky-high.

In the most fascinating and tightly argued section, MacAskill explains why we should welcome population growth as a positive good, vigorously advocating increased fertility. He begins by claiming that “having one extra person in the world is good in and of itself, if that person is sufficiently happy”—a notion that’s superficially self-evident but hotly debated in the field of population ethics, where a prominent scholar once quipped that “we are in favor of making people happy, but neutral about making happy people.”

MacAskill contends that “if your children have lives that are sufficiently good, then your decision to have them is good for them. With a sufficiently good upbringing, having a chance to experience this world is a benefit. And, by the same token, if you have grandchildren, you benefit them, too.” From this conclusion comes another: “If future civilization will be good enough, then we should not merely try to avoid near-term extinction. We should also hope that future civilization will be big.” He means that we should expand the human population as much as possible, including into space. Surveying mountains of survey data, he claims that only some 10 percent of people worldwide are genuinely unhappy, that happiness is correlated with wealth, and that global wealth will only continue to swell in the long run—meaning we can reasonably expect happier people in the future.

But swelling populations mean escalating risks. As global values converge, and as we see the emergence of an artificial general intelligence (AGI), which would be capable of learning and performing tasks at least as well as human beings, we must be wary of oligarchs or other malign actors promulgating, reproducing, and enshrining ideologies that could devastate societies worldwide. So we therefore must carefully monitor the technical progress of AGI and establish international governing bodies to ensure it does not fall into the wrong hands.

More broadly, though, what can we do to ensure a prosperous future? MacAskill urges us to “take robustly good actions, build up options, [and] learn more.” He proposes reducing fossil-fuel usage and developing renewable technology, fostering a diversity of political systems and cultures, and objectively researching the scientific and philosophical issues entailed by extending and enhancing the future of humanity. He also reiterates the injunctions he provided in his 2015 book Doing Good Better, urging his readers to donate their income to effective charities instead of obsessing about personal consumption habits.


MacAskill deserves praise for presenting these issues in a provocative and systematic way that neatly balances realism and optimism. He jars us out of complacency and challenges those who share his ideological inclinations to entertain alternative viewpoints. Still, What We Owe the Future remains an incomplete account that overstates the simplicity of his proposed solutions, neglects much of the good that humanity provides, and underestimates our natural inclination to remain in the here and now.

Take, for instance, the notion of “moral progress.” MacAskill prominently cites the abolition of slavery as the prime illustration of the arc of history bending toward justice because of the contingency of human action, and more specifically, the stirring of a strong moral sense among humanity. But not every moral problem is as cut-and-dried as slavery. MacAskill seeks to enlist “morally motivated heretics who are able to endure ridicule from those who wish to preserve the status quo,” and he hopes that, one day, humanity will regard burning fossil fuels and eating animals as equally barbaric as owning human beings. He can hope away, but it’s worth remembering that  in the 1920s, history seemed to be bending inevitably toward the enlightened view that alcohol so perniciously destroyed society that it merited prohibition.

But perhaps the most striking weakness in What We Owe the Future comes from his inability to explain why we should want to en-sure the future of humanity. As a devotee of Singer and John Stuart Mill, MacAskill characteristically limits his reasoning to net utility, which he mostly defines as human happiness or well-being. Surely all human societies can and do care deeply about ensuring happiness among their populations. But, especially to people of faith or subscribers to traditional ethical philosophies, life entails far more than individual pleasure.

Existence furnishes humanity not merely with the capacity for happiness but with the opportunity to cultivate virtue, to improve ourselves ethically and philosophically—in short, to become better people. We naturally want this for ourselves, for our children, and our grandchildren, and we’d like to think that future humans will be even more virtuous than our own best selves. This notion is largely absent from MacAskill’s thinking. He does identify certain “non well-being goods,” including art, liberal democracy, equality, and the development and dissemination of knowledge, but he devotes a mere two pages to these concepts. Surely scientific discovery and creative expression on their own terms warrant the future proliferation of human beings at least as much as their happiness does.

And in truth, MacAskill’s plea to act now for the sake of the distant future is a tough ask. Most people would struggle to envision how failing to clear the hiking trail of broken glass would affect others hundreds, let alone thousands, of years from now. They would, however, recognize the moral importance of cleaning up after themselves in the here and now because we feel our obligations to the current generation and the world we share. That is why adherents to faith traditions or old-fashioned ethical dictates focus their good deeds on those most directly affected by them today—not necessarily at the expense of our future selves but as a priority over them. This is the temporal equivalent of the “charity begins at home” mandate supplied by the ancient Jewish sages.

In the end, MacAskill offers a bracing and incontrovertible reminder that our decisions today entail long-term consequences for the future of humanity. “Few people who ever live,” he writes, “will have as much power to positively influence the future as we do.” But while there may be more efficient ways of ensuring the survival and thriving of life centuries hence than our current modes of thinking, it will likely be more effective in the long run to cultivate virtue, fellow feeling, and public-spiritedness among today’s human beings as a bridge to future us. Perhaps, for most people, the best way to save the future is to improve the present.

Photo: Graham Hale

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