  A different issue about maximizing rationality concerns the set of desires or aims that is taken as fixed for purposes of applying the requirement of maximization. We may distinguish two basic approaches. The first and perhaps most common of these takes the subjective utility of alternative actions to be determined by the agent’s preferences at the time of deliberation. According to this interpretation of the maximization model, we are rational to the extent we do that which best promotes the totality of our present aims. A second and quite different interpretation results if we expand the set of desires that determine the subjective utilities of outcomes to include the totality of the agent’s preferences over time. According to this model, rational agents aim to maximize the satisfaction of all of their anticipated desires, accepting frustration of present preferences for the sake of greater satisfaction at later times. This interpretation of the maximizing model gives expression to the common idea that a certain prudential regard for one’s own future well-being is a requirement of practical reason (Nagel 1978, chaps 5–8). But if we take it to be a comprehensive account of rationality in action, the prudential interpretation can also appear to be an unstable compromise: if practical reason demands of us impartiality as between our present and future desires, should it not equally demand impartial consideration of the desires of other agents who may be affected by what we do? Why should we take the distinction between persons to be significant for the theory of practical reason, once we have denied such significance to the distinction between different times in the life of a single agent (Parfit 1984; compare section 5 below)?