@EoL Competition

Introduction

Longtermism—the philosophical view that shaping the far future is one of our greatest moral priorities—derives much of its appeal from the vast potential of humanity’s future. Even small actions today, such as reducing existential risk or shaping technological progress responsibly, can ripple forward to affect the existence and flourishing of trillions of lives. However, this reasoning typically assumes that the future, while immense, is finite. If the cosmos is infinite in time or space, the foundations of longtermism face a profound challenge: infinitarian paralysis. In such a context, finite contributions become negligible against infinite totals, threatening to render our choices morally inert. This essay explores the problem of infinitarian paralysis, its implications for decision theory and ethics, and the prospects for preserving longtermism as a practical and intellectually resilient framework.

The Problem of Infinitarian Paralysis

Infinitarian paralysis arises from a simple but devastating observation: in an infinite world, adding or subtracting finite amounts does not alter the total value. Whether we save a million lives, prevent extinction, or enable interstellar flourishing, the outcome still amounts to infinity. Under standard moral theories such as utilitarianism, this creates a deadlock—our actions cannot make the world better or worse if both outcomes contain infinite value.

This challenge undermines the motivational force of longtermism. Its central argument—that reducing risks today secures vast future value—loses traction if that value is already infinite. The paralysis is significant for three reasons. First, it threatens the practical relevance of longtermism in an infinite cosmos. Second, it exposes weaknesses in moral theories that rely on aggregating totals. Third, it highlights a tension between theoretical coherence and practical guidance: ethics must not only describe value but also help us act.

Responses typically take two forms. Some suggest revising moral theories to accommodate infinity, using tools like regularization (evaluating outcomes through cutoffs or trends) or comparative dominance (assessing whether one option is always at least as good as another in every finite segment). Others argue we should resist the assumption of actual infinities in ethical reasoning. Neither solution is straightforward, but ignoring the problem risks leaving longtermism philosophically fragile.

Unstable Decision Theories in Infinite Contexts

The challenge of infinity is not confined to ethics; it destabilizes decision theory itself. Decision theory underpins rational choice, yet when outcomes involve infinite well-being or suffering, finite contributions vanish into irrelevance. Classic paradoxes such as the Infinite Utility Problem, the extended St. Petersburg Paradox, and Comparison Failure illustrate how standard theories collapse in infinite domains.

Philosophers have proposed two main responses. One is to reform decision theories with new mathematical tools—regularization or comparative dominance—to restore action-guidance. The other is to deny that actual infinities should enter ethical or rational reasoning, thereby sidestepping the instability. However, since cosmology leaves open the possibility of infinite futures, dismissing them may appear intellectually evasive. For longtermism, the consequence is clear: if infinite futures make choices incomparable, its action-guiding force weakens. Developing decision theories that function under both finite and infinite assumptions is therefore crucial to its survival.

Normative Uncertainty as a Path Forward

Even if some moral theories collapse under infinity, others may still provide guidance. Tarsney and Wilkinson argue that we should embrace normative uncertainty—the recognition that multiple ethical frameworks, including deontological, virtue-based, or reformed consequentialist approaches, may retain relevance in infinite contexts.

Two strategies have received particular attention. The first approach is regularization, which introduces cutoffs or weighting schemes to render infinite outcomes comparable. The second is comparative dominance, which assesses outcomes segment by segment, allowing us to identify superior actions without appealing to infinite totals. While critics object that these solutions complicate moral reasoning and risk appearing arbitrary, they may be necessary to sustain action-guidance. Normative uncertainty, far from being a weakness, can serve as a strength—encouraging pluralism and resilience in moral reasoning.

The Practical Stakes for Longtermism

The practical stakes of this debate are immense. Longtermism is not an abstract exercise; it actively shapes priorities in philanthropy, global governance, and policy on issues such as AI safety, climate change, and biosecurity. If its intellectual foundation collapses under infinity, its influence on these crucial areas could weaken. Policymakers and citizens may doubt whether existential risk reduction or intergenerational justice has any real significance if infinite futures render all contributions negligible.

Yet the challenge also presents an opportunity. If longtermism succeeds in adapting its ethical tools, it will become more resilient and robust, no longer dependent on fragile assumptions about cosmology. By confronting infinity directly, longtermism could evolve into a framework capable of guiding humanity regardless of whether the future is finite or infinite.

Conclusion

Infinity destabilizes both ethical and decision-theoretic reasoning, generating the problem of infinitarian paralysis and threatening to strip longtermism of its action-guiding force. The options are stark: revise and complicate our moral theories to remain coherent under infinity, or risk irrelevance in a universe that may well be infinite. Though the path forward is contested—through regularization, comparative dominance, or normative pluralism—ignoring the problem is not tenable. The stakes are not merely theoretical but deeply practical, for longtermism aspires to guide humanity’s most consequential choices. By facing the challenge of infinity head-on, longtermism can emerge stronger, more coherent, and more enduring as a philosophy for humanity’s future.