Longtermism

Longtermists have recently argued that it is overwhelmingly important to do what we can to mitigate existential risks to humanity. I consider three mistakes that are often made in calculating the value of existential risk mitigation: focusing on cumulative risk rather than period risk; ignoring background risk; and neglecting population dynamics. I show how correcting these mistakes pushes the value of existential risk mitigation substantially below leading estimates, potentially low enough to threaten the normative case for existential risk mitigation. I (...) use this discussion to draw four positive lessons for the study of existential risk: the importance of treating existential risk as an intergenerational coordination problem; a surprising dialectical flip in the relevance of background risk levels to the case for existential risk mitigation; renewed importance of population dynamics, including the dynamics of digital minds; and a novel form of the cluelessness challenge to longtermism. -/- . (shrink)

What socially beneficial causes should philanthropists prioritize if they give equal ethical weight to the welfare of current and future generations? Many have argued that, because human extinction would result in a permanent loss of all future generations, extinction risk mitigation should be the top priority given this impartial stance. Using standard models of population dynamics, we challenge this conclusion. We first introduce a theoretical framework for quantifying undiscounted cost-effectiveness over the long term. We then show that standard population models (...) imply that there are interventions other than extinction risk mitigation that can produce persistent social benefits. In fact, these social benefits are large enough to render the associated interventions at least as cost-effective as extinction risk mitigation. (shrink)

Political short-termism costs the global economy hundreds of billions to trillions of dollars annually, and leads to many millions of deaths from disasters and suboptimal spending. In this paper, I propose a futures assembly explicitly incentivised to promote the interests of future generations as a promising strategy to ameliorate short-termism. The assembly I propose is governed by citizens randomly selected from among the populace, who are rewarded in the future to the extent that they successfully promote the welfare of future (...) generations. The most initially promising such retrospective accountability mechanism is an iterated mechanism, in which each generation of policymakers rewards the previous generation for their policy choices and for their own evaluation of the previous generation. Such an assembly, supplemented with the duties, powers, and tools that I describe, and with appropriate support from archivists and experts, may manage to represent generations many years into the future. (shrink)

A social planner who evaluates risky public policies in light of the other risks with which their society will be faced should judge favourably some such policies even though they would deem them too risky when considered in isolation. I suggest that a longtermist would—or at least should—evaluate risky polices in light of their prediction about future risks; hence, longtermism supports social risk-taking. I consider two formal versions of this argument, discuss the conditions needed for the argument to be valid, (...) and briefly compare these conditions to some risky policy options with which actual public decision-makers are faced. (shrink)

Many philosophers defend two claims: the astronomical value thesis that it is astronomically important to mitigate existential risks to humanity, and existential risk pessimism, the claim that humanity faces high levels of existential risk. It is natural to think that existential risk pessimism supports the astronomical value thesis. In this paper, I argue that precisely the opposite is true. Across a range of assumptions, existential risk pessimism significantly reduces the value of existential risk mitigation, so much so that pessimism threatens (...) to falsify the astronomical value thesis. I argue that the best way to reconcile existential risk pessimism with the astronomical value thesis relies on a questionable empirical assumption. I conclude by drawing out philosophical implications of this discussion, including a transformed understanding of the demandingness objection to consequentialism, reduced prospects for ethical longtermism, and a diminished moral importance of existential risk mitigation. (shrink)

Longtermists claim that what we ought to do is mainly determined by how our actions might affect the very long-run future. A natural objection to longtermism is that these effects may be nearly impossible to predict — perhaps so close to impossible that, despite the astronomical importance of the far future, the expected value of our present actions is mainly determined by near-term considerations. This paper aims to precisify and evaluate one version of this epistemic objection to longtermism. To that (...) end, I develop two simple models for comparing ‘longtermist’ and ‘neartermist’ interventions, incorporating the idea that it is harder to make a predictable difference to the further future. These models yield mixed conclusions: if we simply aim to maximize expected value, and don’t mind premising our choices on minuscule probabilities of astronomical payoffs, the case for longtermism looks robust. But on some prima facie plausible empirical worldviews, the expectational superiority of longtermist interventions depends heavily on these ‘Pascalian’ probabilities. So the case for longtermism may depend either on plausible but non-obvious empirical claims or on a tolerance for Pascalian fanaticism. (shrink)

The topic of this thesis is how we should treat tiny probabilities of vast value. This thesis consists of six independent papers. Chapter 1 discusses the idea that utilities are bounded. It shows that bounded decision theories prescribe prospects that are better for no one and worse for some if combined with an additive axiology. Chapter 2, in turn, points out that standard axiomatizations of Expected Utility Theory violate dominance in cases that involve possible states of zero probability. Chapters 3–6 (...) discuss the idea that we should ignore tiny probabilities in practical decision-making. Chapter 3 argues that discounting small probabilities solves the ‘Intrapersonal Addition Paradox’ and thus helps avoid the Repugnant Conclusion. Chapter 4 explores what the most plausible version of this view might look like and what problems the different versions have. Chapter 5 focuses on one type of problem, namely, money pumps. The Independence Money Pump, in particular, presents a difficult challenge for those who wish to discount small probabilities. Finally, Chapter 6 discusses the implications of discounting small probabilities for the value of the far future. (shrink)

Like asteroids, hundred-year floods and pandemic disease, thermonuclear war is a low-frequency, high-impact threat. In the long run, catastrophe is inevitable if nothing is done − yet each successive government and generation may fail to address it. Drawing on risk perception research, this paper argues that psychological biases cause the threat of nuclear war to receive less attention than it deserves. Nuclear deterrence is, moreover, a ‘front-loaded good’: its benefits accrue disproportionately to proximate generations, whereas much of the expected cost (...) will be borne in the distant future. Recent surveys indicate that the US and Russian publics assign a surprisingly high likelihood to nuclear war. Nevertheless, earlier research suggests that it is probably not believed to be just around the corner. This, along with the absence of easy solutions, encourages governments and publics to give priority to more pressing concerns. The danger is that the pattern will continue clear up to the point that nuclear war arrives. (shrink)

Discounting future costs and benefits is often defended on the ground that our descendants will be richer. Simply to treat the future as better off, however, is to commit an ecological fallacy. Even if our descendants are better off when we average across climate change scenarios, this cannot justify discounting costs and benefits in possible states of the world in which they are not. Giving due weight to catastrophe scenarios requires energetic action against climate change.

The asymmetry is the view in population ethics that, while we ought to avoid creating additional bad lives, there is no requirement to create additional good ones. The question is how to embed this intuitively compelling view in a more complete normative theory, and in particular one that treats uncertainty in a plausible way. While arguing against existing approaches, I present new and general principles for thinking about welfarist choice under uncertainty. Together, these reduce arbitrary choices to uncertainty-free ones, regardless (...) of how the latter should be made. I illustrate these principles by developing two theories of the asymmetry, reflecting different views about the non-identity problem. In doing so, I clarify some other major choice-points, presenting new arguments that creating additional good lives can justify (but not require) doing harm. Finally, I consider what the developed theories have to say about the importance of extinction risk and the long-run future. (shrink)