Multiple selves is a conventional assumption in behavioural welfare economics for modelling intrapersonal well-being. Yet an important question is which self has normative authority over the other. In this paper, we tackle this ethical question from the ontological question of personal persistence: what does it take for an individual to persist from one time to another? We review the main theories of personal persistence offered in analytic philosophy and discuss the philosophical problems related to the alternative unified assumptions of the self offered in the critical literature of behavioural welfare economics. We discuss two main issues. First, most of the authors defending a unified account of the self in normative economics tend to consider the question of identity over time from an ethical viewpoint but not from an ontological viewpoint. We argue that the ethical viewpoint is misleading because it reduces the question of personal persistence to the question of personhood. Second, we discuss the fact that the alternative assumptions of the unified self endorsed in the critical literature of behavioural welfare economics assume the narrative view of personal persistence. Because of its many philosophical objections, we however argue that the narrative view cannot provide a satisfying account of identity.