 To counter the contention that, at the outset, practical rationality calls for the minimization of net costs (or the maximization of net benefits), Rawls and Nozick need to hold that what makes it practically rational for a given individual to incur some cost to herself (or forego some benefit for herself) is the avoidance of some greater cost to herself (or the attainment of some greater benefit for herself). They need to hold that (at least absent further argument) the rational balancing of costs incurred (or benefits foregone) and costs avoided (or benefits attained) must take place within lives and not across lives. And this does seem to be part of the intended force of Rawls’ invocation of a “plurality of distinct persons with separate systems of  ends”[6]  and of Nozick’s insistence that there are “only individual people, different individual people, with their own individual lives” (33). In Nozick this stance is most explicit when he parses “the fact of our separate existences” as,