 A supposed advantage of this approach is its ability to explain the rationality of behaviors that seem intuitively sensible, but that are hard to fit into the consequentialist scheme (such as commitments deriving from one’s past involvement in an activity or project, which can look like an irrational weighting of ‘sunk costs’ to the consequentialist; compare Nozick 1993). But defenders of the consequentialist model contend that we can account in terms of it for rational actions that appear to resist treatment in consequentialist terms. For instance, if friends have special, ‘agent-relative’ reasons to attend to the interests of each other—and not merely reasons to promote the neutral value of friendship wherever it may be instantiated—this can be expressed in consequentialist terms by introducing person-indexed value functions, which rank possible states of affairs in terms of their desirability from the agent’s point of view (Sen 2000).