In What We Owe the Future, philosopher William MacAskill attempts a moral reorientation of historic proportions. His thesis is disarmingly simple but ethically radical: future people matter, there may be an extraordinary number of them, and we can significantly affect the quality of their lives. From this, he argues, flows a powerful imperative—longtermism—the idea that influencing the long-term future should be among our highest priorities.
Longtermism, unpacked
MacAskill builds his case through a blend of thought experiments, historical analogies, and quantitative forecasting. He begins by asking us to imagine living every human life in chronological order—a jarring reminder of just how brief the modern era is relative to human history, and how vast the future could be. If humanity survives even a modest portion of the time Earth remains habitable (let alone if we become an interstellar species), almost all human lives will be lived in the future. The stakes of our decisions today, then, are potentially astronomical.
What follows is a tour through the moral, empirical, and practical scaffolding of longtermist thought. MacAskill addresses obvious challenges: Can we really predict long-term consequences? How can we prioritize distant lives when current suffering remains urgent? His answer is cautious optimism. History offers precedents—slavery abolition, the U.S. Constitution, even Shakespearean poetry—that have had millennia-spanning impacts. Today’s choices, especially around AI, biotechnology, and global governance, may have similarly durable effects.
Trajectory shifts and existential risks
The book distinguishes two primary ways of influencing the future: safeguarding civilization’s survival and steering its trajectory. The former involves minimizing existential risks—events that would cause human extinction or irrevocable collapse, such as engineered pandemics or AI misalignment. The latter, more subtle but perhaps equally consequential, concerns shaping the moral direction of society. If our values become “locked in” by powerful technologies or authoritarian regimes, they may guide billions of lives across millennia.
Here MacAskill is at his most philosophically ambitious, using a "Significance-Persistence-Contingency" framework to assess how our actions might echo across time. He urges a careful, probabilistic mindset—a willingness to act under uncertainty when the stakes are high.
Critical lens and review
While the book is admirably clear and earnest, its framing is not without controversy. Some readers may find the utilitarian undercurrent alienating, especially its speculative arithmetic of lives unborn. Others may argue that the urgency of climate justice, inequality, and political instability today risks being eclipsed by abstract futurism. MacAskill does attempt to address this tension, emphasizing that longtermist goals can (and often do) align with short-term improvements—such as decarbonization, which benefits both current and future generations.
More troubling is the question of epistemic humility. Predicting the values, desires, and dangers of the next million years may be a project as hubristic as it is noble. Yet, MacAskill’s tone is refreshingly open and self-critical. He acknowledges the book as an early attempt to map a vast and uncertain moral terrain.
Final take
Ultimately, What We Owe the Future is less a definitive guide than an invitation to think at planetary and civilizational scale. It challenges readers to stretch their moral imaginations—and their timelines. Whether or not one fully embraces longtermism, MacAskill offers a vital prompt: to see ourselves not just as heirs of history, but as ancestors.
