Abstract: Prompted by Derek Parfit's early work on personal identity, Lewis advances the view that persons are best regarded as suitably related aggregates of person-stages. Parfit argues that what matters in survival is either identity or mental continuity and connectedness; that the two cannot both be what matters in survival (because the former is a one-one relation and does not admit of degree, whereas the latter can admit of degree and may be a one-many or many-one relation); and that what matters in survival is not identity. Contra Parfit, Lewis contends that the opposition is a false one, since it obscures the fact that mental continuity and connectedness is a relation between two person-stages (i.e., time-slices of continuant persons), whereas identity is a relation between temporally extended continuant persons with stages at different times. The postscript includes both Lewis’ rejoinder to Parfit's objections, as well as a further defense of person-stages.

Keywords: fission, fusion, identity, i-relation, Derek Parfit, John Perry, personal identity, person-stages, R-relation, survival, what matters in survival,