Derek Parfit’s thesis that identity doesn’t matter in survival has been extensively discussed except for its metaphysical robustness. How can we justify the abandonment of identity in the way Parfit suggests? My argument is the following. Those who want to endorse the thesis that identity doesn’t matter (and, therefore, abandon identity across time) should adopt exdurantism, i.e. a metaphysics according to which the world is composed by temporal parts each existing at a time and according to which there is nothing (...) as a numerically same entity which exists at different times. I show that the metaphysics behind Parfit’s theory is neither compatible with endurantism, according to which object persists by being wholly present at different times, nor with perdurantism, according to which entities are aggregates of temporal and spatial parts. (shrink)

Traditionally, this puzzle has been solved in various ways. Aristotle, for example, distinguished between “accidental” and “essential” changes. Accidental changes are ones that don't result in a change in an objects' identity after the change, such as when a house is painted, or one's hair turns gray, etc. Aristotle thought of these as changes in the accidental properties of a thing. Essential changes, by contrast, are those which don't preserve the identity of the object when it changes, such as when (...) a house burns to the ground and becomes ashes, or when someone dies. Armed with these distinctions, Aristotle would then say that, in the case of accidental changes, (1) and (2) are both false—a changing thing can really change one of its “accidental properties” and yet literally remain one and the same thing before and after the change. (shrink)

An introduction to the theories of endurantism and perdurantism, and persistence more broadly.