Review Materials for Chapter 4 – The Problem of Personal Identitiy
Section 4.1 - We are such Stuff as Dreams are Made On: Self as Substance
1. The problem of personal identity is a version of the problem of change: How can something change and yet
remain the same thing?
2. Something at one time is numerically identical to something at another time if and only if they are one and
the same thing. Two things are qualitatively identical if and only if they share the same properties.
3. 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.
4. 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.
5. 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.
6. Living things like plants or animals retain their identity as long as they retain their functional organization.
7. Persons are generally considered to be rational, self-conscious beings that have free will.
They have full moral standing, including the right to life.
8. Our judgments of personal identity are based on physical features. This has led some to embrace animalism,
the doctrine that identical persons are identical living human animals.
9. 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.
10. The vegetable case thought experiment.
Imagine that you lapse into a persistent vegetative state and that as a result your higher cognitive functions
are destroyed and that the loss is permanent.
Is the human animal that results when the cerebrum is destroyed strictly and literally you, or is it no more
you than a statue erected after your death would be you?
11. 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.
12. Locke's tale of the prince and the cobbler shows that body switches are possible. So having the same body is
not a necessary condition for being the same person.
13. The Brain 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?
14. The avoidance of future great pain case.
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.
15. 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.
16. 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?
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17. 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.
18. Leibniz’s King of China thought experiment:
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.
19. Locke’s Nester and Thersites thought experiment.
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.
20. 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.
Section 4.2 - Golden Memories: Self as Psyche
1. Our memories seem essential to us because if we lost them, there is reason to believe that we would cease to
exist.
2. According 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.
3. The 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.
4. 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.
5. The 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.
6. 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.
7. The inconsistency in Locke's memory theory can be eliminated by accepting indirect as well as direct
memories.
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8. 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.
9. 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.
10. The Circularity Objection.
Butler argues that Locke's memory theory is circular because the only way to distinguish real from apparent
memories is to appeal to the notion of personal identity.
11. 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.
a. The circularity of Locke's memory theory can be eliminated by adopting Shoemaker's notion of quasimemory.
12. Quasi-memories.
Someone 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.
13. The 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.
14. A person quasi-desires something if and only if they have a desire that is caused in the right way by an actual
desire.
15. Quasi-desires.
To quasi desire something you don’t have to be identical to the person who originally had the desire.
16. Two people are psychologically connected if they can consciously quasi-remember and quasi-desire the same
things.
17. Two people are psychologically continuous if they form part of an overlapping series of persons who are
psychologically connected with one another.
18. 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.
19. The 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.
20. Williams’s’ Guy Fawkes thought experiment.
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.
21. 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.
22. 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?
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23. Williams reduplication argument and Parfit's transporter tale show that there must be more to personal
identity than psychological continuity because more than one person can be psychologically continuous to
another.
Section 4.3 - You Can't Step Into the Same River Twice: Self as Process
1. Perhaps the reduplication problem can be avoided by requiring that one’s psychology be caused by and
realized in the same brain.
2. Shoemaker’s Brain Transplant.
Suppose that it’s possible to perform brain transplants.
Suppose further that the brains of Brown and Robinson are switched so that Brown’s brain is in Robinson’s
body and vice versa.
Wouldn’t the body with Brown’s brain be Brown?
3. According to the brain theory, identical persons are those who are psychologically continuous with one
another and whose psychology is caused by and realized in the same brain.
4. Trying to avoid the reduplication problem by requiring one's psychology to be caused by and realized in the
same brain won't work either because, as Parfit shows, you could survive a split brain operation. It's possible
for more than one person to be both psychologically and physically continuous with another.
5. In patients who have undergone “split-brain surgery,” there seems to be two centers of consciousness; “two
wills in one cranial vault.”
So perhaps just as our entire body in not essential to us, neither is our entire brain.
6. Parfit’s Division thought experiment. Suppose that Parfit’s brain hemispheres have the same psychology and
that Parfit is one of three identical triplets.
Now suppose that his body is injured as well as the brains of his two identical brothers and that each half of
his brain is transplanted into the body of one of his brothers.
Which of the brothers is Parfit?
7. Personal identity cannot consist in psychological or physical continuity because identity is a relation that can
hold only between a thing and itself.
8. To avoid the reduplication problem, it seems that a theory of personal identity must either rule out any sort
of splitting, or it must have some means of determining which branch is identical to the original.
9. According to the non-branching theory, identical persons are those who are psychologically continuous with
one another and whose causal connection has not branched.
In this view, neither of the surviving triplets would be Parfit.
10. According to the closest continuer theory, identical persons are those who are closest continuers of one
another.
In this view, neither of the surviving triplets would be identical to Parfit because they are both equally close
continuers.
11. According to the only x and y principle, whether one thing, x, is identical to another thing, y, can depend
only on facts about x and y.
Both the non-branching theory and the closest continuer theory reject this principle.
12. It’s commonly assumed that we can survive the death of our bodies only if we’re numerically identical to
someone who exists after our body dies.
Perhaps all that is needed for survival is psychological continuity.
13. It’s commonly assumed that we can be held responsible for an action only if we are numerically identical to
the person who performed it.
Perhaps all that is needed for responsibility is psychological continuity.
14. Although psychological continuity is not sufficient for identity, it seems sufficient for praise and blame.
Parfit’s Reformed Nobelist.
“Suppose that a man aged ninety, one of the few rightful holders of the Nobel Peace Prize, confesses that it
was he who, at the age of twenty, injured a policeman in a drunken brawl.”
Should we now punish him for that crime?
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15. We have been unable to find a set of necessary and sufficient conditions for personal identity. Why is that?
Perhaps the best explanation is that the self is not a thing but a process.
16. Only those persons who have the concepts of rights and wrong and can act on those concepts are held
accountable for what they do.
These people are known as “moral agents.”
For example, the very young, the mentally incapacitated, and the insane may not be moral agents.
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