On Identity:
1. Qualitative vs. Numerical.
Qualitative identity holds between two things, when
they share all their (relevant) properties.
Numerical identity is a thing’s self-identity— it’s not
a relation between two things at all. Instead, it turns
on the distinctness of that thing from other things.
2. The same X:
Some things persist through time—most ordinary
objects are like this: The sun, earth and moon, trees
and streams, cars, dogs, keys, statues and buildings,
and, of course, human beings.
But persisting things can go through many changes
through time:
From acorn to oak; from infant to child to adult to…;
from a ship fresh from the shipyard to the old,
extensively repaired vessel 50 years later; from
mainstream yellow star to red-giant to white dwarf to
stellar cinder; etc.
3. Same Person—Various proposals:
1. Same body, same person:
2. Same soul, same person:
3. Same brain, same person:
4. Same memories/character/etc., same person:
5. Psychological continuity, same person: