2Memory TheoryAccording to the memory theory, identical persons are those who share at least one experience memory.Consequences:Persons can switch bodies as long as they retain their memories.Two persons can inhabit the same body as long as they have different memories.
3The Inconsistency Objection Most people forget a good deal of what has happened to them.If you lose all memory of some part of your life, does that mean that you are no longer identical to the person who was in your body at that time?Locke would seem to think so.
4Thought Experiment: Reid’s Tale of the Brave Officer and the Senile General Suppose a brave officer who stole a flag from an enemy also stole an apple from an orchard when he was a boy.A senile general remembers stealing the flag but not stealing the apple.According to Locke, the senile general is identical to the brave officer but not the boy.
5The Transitivity of Identity If A is identical to B, and if B is identical to C, then A is identical to C.For example, if Mark Twain is identical to Samuel Clemens and Samuel Clemens is identical to the author of Huckleberry Finn, the Mark Twain is identical to the author of Huckleberry Finn.
6The Inconsistency Objection Locke’s theory is inconsistent because it violates the transitivity of identity.The senile general is identical to the brave officer and the brave officer is identical to the boy but the senile general is not identical to the boy.
7Direct Memory vs. Indirect Memories A direct memory is a memory that a person can consciously recall.An indirect memory is a memory that an earlier stage of a person can recall.
8Real Memories vs. Apparent Memories A real memory is a memory of an event that was experienced by the person remembering it and was caused by the event it records.An apparent memory is a memory of an event that either didn’t happen or wasn’t caused by the event it records.
9The Circularity Objection Only real memories can serve as the basis of personal identity.But real memories can’t be used to explain personal identity because the explanation would be circular.Real memories are defined in terms of personal identity so they can’t be used to define personal identity.
10Quasi-MemoriesSomeone quasi-remembers an experience if and only if they have an apparent memory that was caused in the right way by an actual experience.To quasi remember something, you don’t have to be identical to the person who had the experience.
11Quasi-Memories and Personal Identity Quasi-memories are not defined in terms of personal identity.Thus they can be used to provide a non-circular definition of personal identity.
12The Insufficiency Objection Who we are seems to be determined not only by our memories, but also by our desires and intentions.If our desires and intentions changed radically enough, there would be reason to think that we had ceased to exist.
13Quasi-DesiresA person quasi-desires something if and only if they have a desire that is caused in the right way by an actual desire.To quasi desire something you don’t have to be identical to the person who originally had the desire.
14Psychological Connectedness vs. Psychological Continuity Two people are psychologically connected if they can consciously quasi-remember and quasi-desire the same things.Two people are psychologically continuous if they form part of an overlapping series of persons who are psychologically connected with one another.
15Psychological Continuity Theory According to the psychological continuity theory, identical persons are those who are psychologically continuous with one another.To survive the death of your body, you only have to be psychologically continuous with someone who lived before.
16The Reduplication Problem Those who believe in reincarnation believe that people born at different times can be psychologically continuous with one another.The question is whether psychological continuity is enough to make people living at different times identical.
17Thought Experiment—Williams’ Reincarnation of Guy Fawkes Suppose Charles undergoes a sudden and violent change of character.Suppose further that he now has Guy Fawkes memory and character.So Charles is psychologically continuous with Guy Fawkes.
18Thought Experiment: Williams’s Reduplication Argument If it’s possible for Charles to undergo those sorts of psychological changes, it’s possible for his brother Robert to undergo them as well.But it’s not possible for two different people to be numerically identical.So psychological continuity is not sufficient for identity.
19Thought Experiment: Parfit’s Transporter Tale Suppose it was possible to teletransport people from one location to another.Suppose further that a replica of oneself was transported while the original was kept intact.Would the replica be you?
20Thought Probe: Transporter Travel Suppose that it became technically possible to teletransport a human from one place to another.Would you use the teletransporter? Why or why not?What theory of personal identity lies behind your decision?
21Thought Experiment: Bodily Torture Suppose someone tells you that the person in your body is going to be tortured tomorrow.That person, however, will have none of your memories and you will have no memory of being tortured.Should you fear being tortured? Will you ever be conscious of being tortured?