The American philosopher John Rawls describes a fair system of social cooperation as one that is both rational and reasonable. Is it rational and reasonable for societies that (1) are vulnerable to diverse risks of morbidity (e.g., cancer, heart disease) and mortality and (2) are constrained by limited medical resources, to prioritize aging research? In this paper I make the case for answering "yes" on both accounts. Focusing on a plausible example of an applied gerontological intervention (i.e., an antiaging pharmaceutical), I argue that the goal of decelerating the rate of human aging would be a more effective strategy for extending the human health span than the current strategy of just tackling each specific disease of aging. Furthermore, the aspiration to retard human aging is also a reasonable aspiration, for the principle that underlies it (i.e., the duty to prevent harm) is one that no one could reasonably reject.