A coldly rationalist individualist can deny that he has any obligation to make sacrifices for the future.

Hardin is pointing to a moral and political vulnerability in strict rational-choice individualism: if a person recognizes only immediate self-interest and rejects any binding duties to others or to posterity, then appeals to conserve resources, accept limits, or bear costs for long-term collective benefit can be dismissed as irrational. The line fits Hardin’s broader preoccupation with population, commons dilemmas, and the need for social constraints to prevent short-term incentives from degrading shared resources. It implies that sustaining a livable future requires norms, institutions, or ethics that extend obligation beyond the present self—because purely “cold” rationalism can rationalize free-riding on the sacrifices of others.