 Unless, that is, one allows that the relations that matter  in identity can hold interpersonally, in which case a number of  interesting possibilities arise. For instance, Brink argues that the  possibility of interpersonal continuity supports a kind of  consequentialism via rational egoism. If one is a rational egoist,  one will aim to promote one's own good. What counts as one's  own, though – what counts as contained within the  prudentially significant metaphysical unit – given  reductionism, is defined by psychological continuity (Brink argues  against the coherence or practical feasibility of both atoms and  selves as the basic units). But if continuity also holds  interpersonally, then the rational egoist must, if truly rational,  promote the good of all those with whom he is continuous, which,  given the thought that each of us bears only six degrees of  separation from every other person, generates an important kind of  impartial, universalist consequentialism: “the egoist  can recognize derivative but non-instrumental reason to be concerned  about others” (Brink 1997b, 127). Of course, if the utter  impartiality of a universalist consequentialism is implausible for  the way it overlooks the importance to us of the special concern we  have for friends and loved ones, perhaps one can introduce the idea  of degrees of continuity, in which case the concern the  egoist must have for others “is proportional to the amount of  psychological continuity that exists between the agent and  others” (Ibid., 128; see also McMahan 2002, 59–66).