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Chapter 4The Problem of Personal Identity
The Problem of Change
• How can something change and yet remain the same thing?
• If something changes, it’s different. And if it’s different, it’s no longer the same.
Qualitative vs. Numerical Identity
• Two objects are qualitatively identical if and only if they share the same properties (qualities); two cue balls from the same manufacturer, for example.
• Two objects are numerically identical if and only if they are one and the same; Mark Twain and Samuel Clemens, for example.
Accidental vs. Essential Properties
• An accidental property is one that something can lose without ceasing to exist. Your hair being a certain length, for example, is an accidental property of you.
• An essential property is one that something cannot lose without ceasing to exist. Your being a person, for example, is an essential property of you.
Thought Probe:A Different Person
• Kathleen Soliah certainly seems to be a qualitatively very different person than she was in the 1970s.
• Is she numerically different?• Is she different enough that she should get a
reduced sentence?
Section 4.1We Are Such Stuff asDreams are Made On
Self as Substance
Locke on Identity Conditions
• Masses of matter like rocks or lumps of clay retain their identity as long as they retain the atoms out of which they are made.
• Living things like plants or animals retain their identity as long as they retain their functional organization.
Thought Probe: Hobbes’s Ship of Theseus
• Suppose that the planks in Theseus’s ship have been replaced one by one over the years until none of the original planks remained.
• Suppose further that the original planks were saved and put back into their original order.
• Which ship is identical to the original?
Persons
• Persons are generally considered to be rational, self-conscious beings that have free will.
• They have full moral standing, including the right to life.
Non-human persons
• According to animalism, there can be no non-human persons.
• But rational, self-conscious computers, aliens, and animals seem possible.
• So being a human may not be a necessary condition for being a person.
Animalism
• Animalism is the doctrine that identical persons are identical human animals.
• According to animalism, once our bodies die, we cease to exist.
• So our only hope for eternal life is some form of resurrection.
Humans Who are Not Persons
• Those who have fallen into a permanent vegetative state are no longer capable of being rational or self-conscious.
• Even though they have a living, human body there is reason to think that they are no longer persons.
• So being a human may not be a sufficient condition for being a person.
Body Switches
• According to animalism, it’s impossible for one person to inhabit two different bodies.
• But body switches as portrayed in the movies Big, Heaven Can Wait, All of Me, Freaky Friday, etc., seem possible.
• So having the same body may not be a necessary condition for being the same person.
Thought Experiment: Locke’s Tale of the Prince and the Cobbler
• “For should the Soul of a Prince, carrying with it the consciousness of the Prince’s past life, enter and inform the Body of a Cobbler…every one sees, he would be the same Person with the Prince.”
• If such body switches are possible, animalism is false.
Thought Experiment: The Transplant Case
• Imagine that an ingenious surgeon removes your cerebrum and implants it into another head.
• Are you the biologically living but empty-headed human being that has inherited your vegetative functions?
• Or are you the person who ends up with your cerebrum and your memories?
• Or are you dead?
Thought Experiment: Unger’s Great Pain
• Imagine you’re about to undergo a brain transplant.
• Unger asks whether you would choose to have yourself suffer considerable pain before the transplant to prevent the person with your brain from suffering even greater pain afterwards.
• If so, animalism is false.
Siamese Twins
• Some Siamese twins have two heads but one body.
• Is this a counterexample to animalism?• Can animalism be modified to account for this
counterexample?
Multiple Persons, One Body
• According to animalism, it’s impossible for one body to contain two persons.
• But in the case of multiple personality disorder, split-brain patients, and Siamese twins, it seems as if there are two persons in one body.
• So having the same body may not be sufficient for being the same person.
Soul Theory
• According the soul theory, identical persons are those with identical souls.
• As long as your soul exists, you exist.• But what are the identity conditions for souls?
What is it for one soul to be identical to another soul?
Souls and Thoughts
• Souls are thinking substances. They are not thoughts; they are things that think.
• The relation between a soul and its thoughts can be likened to the relation between a pincushion and its pins.
• Just as a pincushion can have different pins in it at different times, the same soul can have different thoughts in it at different times.
Thought Experiment: The King of China
• Suppose someone offered to make you the King of China on the condition that you lose all of your memories.
• In such a case, it’s doubtful that you would be around to enjoy the wealth even though, presumably, your soul would be.
• So having the same soul may not be a necessary condition for being the same person.
Thought Experiment: Nestor and Thersites
• Suppose that all of your thoughts and memories were transferred to a soul that once housed those of Nestor or Thersites.
• That would not make you identical to Nestor or Thersites.
• So having the same soul may not be a necessary condition for being the same person.
Kant’s Soul Switch
• “If…we postulate substances such that the one communicates to the other representations together with the consciousness of them, we can conceive a whole series of substances….The last substance would then be conscious of all the states of the previously changed substances as being its own states.”
• So identity goes—not where your soul goes—but where your consciousness goes.