Personal Identity, What Is It? (Notes from An Old Lecture I Once Gave)-Slightly Edited

I used to give this lecture in one of my classes.

The question of personal identity, what is it? Think about the self in association with the so-called "afterlife." Let's assume that the body theory is true: it asserts that I am numerically identical with my body. There is no numerical difference between me and my physical body. Furthermore, assuming materialistic premises (i.e., that only matter exists), let us assume that I have no soul or immaterial aspect which characterizes my existence. If I temporarily cease to exist, but then God later causes me to exist again whereby I have the same molecular structure as before, then could it be said that God has resurrected the same person who existed previously?

What if my personality is not the same as it was in this life. I am nicer, more joyful, I no longer spend my days thinking about theoretical puzzles, nor do I remember the trauma experienced when I was fifteen years old. With all these differences, is it still me existing in the world to come? 

Next, what are acceptable criteria for personal identity? A) As stated above, one criterion could be bodily identity. For instance, using DNA testing to identify someone. Also we could use fingerprints to mark someone's identity or conclude that a person is the same individual if he/she is resurrected with the same cerebral properties that were possessed antemortem. But suppose that brain transplants become possible, which would result in a person having the same body, but a different brain? Would someone who experienced a brain transplant still be the same person? Why or why not?

B) What about the same memories being the criterion for securing personal identity. Let's say that I had my first ice cream cone in 1970, and remember that first experience later in 1999. Also assume that my memory of the event is genuine: it is truly my memory. But Thomas Reid raises the problem of intransitive relations whereby an elderly person might remember what happened when they were forty or fifty, but forget what occurred at age five. See page 201 of Bruce Waller, Consider Philosophy, 2011 Edition.

Another potential conundrum is the problem of two hemispheres being split between two distinct bodies (Waller, page 202). Yet another difficulty is that the memory theory seems circular. See https://www3.nd.edu/~jspeaks/courses/mcgill/201/winter2005/memory-theory.html

C) Soul theory. This theory claims that if someone has the same soul over different times (T1, T2, T3 . . . Tn), then he/she is the same person. Yet how does one go about stipulating the criteria for this theory? See p. 204 of Waller. Moreover, will appealing to a mysterious entity like the soul help when it comes to securing identity?

D) Narrative self-p. 204-205 of Waller. Is the "self" an entity that we construct? If so, what events in your life have contributed to your personal narrative? What are some potential difficulties with the narrative account of personal identity? See Waller, page 205. Note the modular brain and narrative model on Waller, p. 206-208. 

Lastly, consider the problem known as Theseus' ship. What do you think about this challenge to personal identity through time?

[Personally, I like the way that Nancey Murphy addresses questions of identity.]