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.