DebateLabKIT/deepa2-corpus · Datasets at Hugging Face

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of some other entity ” (ibid., 228).
P12. We do not have good evidence for the belief in reincarnation (ibid.).
Neither do we have evidence for the existence of Cartesian egos (i.e.,
thinking nonmaterial substances); it seems like they are neither “ publicly
observable ” nor “ privately introspectible facts ” (ibid.).
A Reductionist Account of Personal Identity 85
P13. There are no other reasons than the ones in P10, P11, and P12 to
believe in the existence of a separately existing subject of experiences.
C5. We have no evidence for the claim that we are separately existing
entities (P10, P11, P12, P13).
C6. We should reject the belief that persons exist as separately existing
entities ( modus ponens , P9, C5).
C7. The reductionist view is true ( modus ponens , P4, C1, C6).
21
Split - Case Arguments about
Personal Identity
Ludger Jansen
Parfi t , Derek . Reasons and Persons . Oxford : Oxford University Press , 1984 .
Shoemaker , Sydney , and Richard Swinburne . Personal Identity (Great
Debates in Philosophy) . Oxford : Blackwell 1984 .
In the empiricist tradition, it is a common move to account for the diachronic
identity of a person in terms of shared mental properties or continuity
of memories (e.g., Locke) or in terms of shared matter, especially of
the brain. But all these criteria allow for “ split cases, ” that is, for two or
more candidates fulfi lling the requirements, which cause trouble with the
formal properties of the identity relation (i.e., refl exivity, symmetry, and
transitivity). For example, a brain can be divided and both halves implanted
in different bodies: which of these, if any, is the same person as the original
one? Two individuals could even share most of their memories – but this
does not make them the same person. Thus, none of these criteria can be
the decisive factor for personal identity. Some philosophers, such as Richard
Swinburne (#24), argue for dualism and conclude that there must be some
immaterial factor, the soul, that accounts for personal identity. Others, such
as Derek Parfi t, conclude that we should discard the concept of personal
identity altogether and rather replace it with a nonsymmetric successor
relation that allows for such split cases.
Just the Arguments: 100 of the Most Important Arguments in Western Philosophy,
First Edition. Edited by Michael Bruce and Steven Barbone.
© 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.
Split-Case Arguments about Personal Identity 87
There are no logical diffi culties in supposing that we could transplant one
of [a person] P 1 ’ s [brain] hemispheres into the skull from which a brain had
been removed, and the other hemisphere into another such skull, and that
both transplants should take, and it may well be practically possible to do
so. [ … ] If these transplants took, clearly each of the resulting persons would
behave to some extent like P 1 , and indeed both would probably have some
of the apparent memories of P 1 . Each of the resulting persons would then be
good candidates for being P 1 . After all, if one of P 1 ’ s hemispheres had been
destroyed and the other remained intact and untransplanted, and the resulting
person continued to behave and make memory claims somewhat like those
of P 1 , we would have had little hesitation in declaring that person to be P 1 .
The same applies, whichever hemisphere was preserved [ … ]. But if it is, that
other person will be just as good a candidate for being P 1 . [ … ] But [ … ] that
cannot be – since the two persons are not identical with each other. (Shoemaker
and Swinburne, 15)
P1. A 1 and A 2 are two distinct persons.
P2. At t 2 > t 1 , A 1 and A 2 are such that each of A 1 and A 2 share exactly the
same amount of the X that A had at t 1 .
P3. X is the decisive factor for personal identity (e.g., body mass, brain
mass, memories, character traces), that is, for any persons A 1 and A 2 and
any times t 1 and t 2 , if A 2 has at t 2 most of the X that A 1 had at t 1 , then
A 1 and A 2 are the same person (assumption for reductio ).
C1. A 1 is the same person as A ( modus ponens , P3, P2).
C2. A 2 is the same person as A ( modus ponens , P3, P2).
P4. If X is the same person as Y, then Y is the same person as X (symmetry
of identity).
C3. A is the same person as A 2 ( modus ponens , P4, C2).
P5. If A 1 is the same person as A and A is the same person as A 2 , then A
is the same person as A 2 (transitivity, C1, C3).
C4. A 1 is the same person as A 2 ( modus ponens , conjunction, P5, C1,
C3).
C5. No such X can be the decisive factor for personal identity ( reductio ,
P1 – C4).
22
The Ship of Theseus
Ludger Jansen
Hobbes , Thomas . “ De corpore , ” in The English Works of Thomas Hobbes ,
Vol. 1 , edited by Sir William Molesworth . London : John Bohn , 1839 .
Plato . Phaedo , in Five Dialogues , 2nd edn. , translated by G. M. A. Grube,
revised by J. M. Cooper, 93 – 154 . Indianapolis : Hackett , 2002 .
Plutarch . “ Life of Theseus , ” in Lives , translated by Bernadotte Perrin, vol.
I , 1 – 87 . Cambridge, MA : Harvard University Press , 1967 .
The “ Ship of Theseus ” is an intriguing puzzle about identity through time.
It is based on the custom of the Athenians to send Theseus ’ ship each year
on a sacred voyage to Delos, because it was believed that Apollo once saved
the lives of Theseus and his fourteen fellow - travellers. The ritual was annually
repeated for a long time, and hence the ship needed continual repair,
new planks being substituted for the old ones. Plutarch relates to us that
already the Athenian philosophers had discussed whether the ship is still
the same ship although it consists, after a while, entirely of new planks
(Plutarch, “ Life of Theseus ” § 22 – 3; cf., Plato, Phaedo 58a – c). Hobbes put
a sophisticated twist to the story: Suppose, he said, that someone collected
the old planks and put them together again in the end, thus restoring the
old ship. The same ship, then, seems to exist twice, which is absurd. Hobbes
used this argument to support his version of relative identity: the original
ship T1 and the restored ship T2 share the same matter, whereas the original
ship and the repaired ship T3 share the same form.
Just the Arguments: 100 of the Most Important Arguments in Western Philosophy,
First Edition. Edited by Michael Bruce and Steven Barbone.
© 2011 Blackwell Publishing Ltd. Published 2011 by Blackwell Publishing Ltd.

of some other entity ” (ibid., 228).

P12. We do not have good evidence for the belief in reincarnation (ibid.).

Neither do we have evidence for the existence of Cartesian egos (i.e.,

thinking nonmaterial substances); it seems like they are neither “ publicly

observable ” nor “ privately introspectible facts ” (ibid.).

A Reductionist Account of Personal Identity 85

P13. There are no other reasons than the ones in P10, P11, and P12 to

believe in the existence of a separately existing subject of experiences.

C5. We have no evidence for the claim that we are separately existing

entities (P10, P11, P12, P13).

C6. We should reject the belief that persons exist as separately existing

entities ( modus ponens , P9, C5).

C7. The reductionist view is true ( modus ponens , P4, C1, C6).

21

Split - Case Arguments about

Personal Identity

Ludger Jansen

Parfi t , Derek . Reasons and Persons . Oxford : Oxford University Press , 1984 .

Shoemaker , Sydney , and Richard Swinburne . Personal Identity (Great

Debates in Philosophy) . Oxford : Blackwell 1984 .

In the empiricist tradition, it is a common move to account for the diachronic

identity of a person in terms of shared mental properties or continuity

of memories (e.g., Locke) or in terms of shared matter, especially of

the brain. But all these criteria allow for “ split cases, ” that is, for two or

more candidates fulfi lling the requirements, which cause trouble with the

formal properties of the identity relation (i.e., refl exivity, symmetry, and

transitivity). For example, a brain can be divided and both halves implanted

in different bodies: which of these, if any, is the same person as the original

one? Two individuals could even share most of their memories – but this

does not make them the same person. Thus, none of these criteria can be

the decisive factor for personal identity. Some philosophers, such as Richard

Swinburne (#24), argue for dualism and conclude that there must be some

immaterial factor, the soul, that accounts for personal identity. Others, such

as Derek Parfi t, conclude that we should discard the concept of personal

identity altogether and rather replace it with a nonsymmetric successor

relation that allows for such split cases.

Just the Arguments: 100 of the Most Important Arguments in Western Philosophy,

First Edition. Edited by Michael Bruce and Steven Barbone.

Split-Case Arguments about Personal Identity 87

There are no logical diffi culties in supposing that we could transplant one

of [a person] P 1 ’ s [brain] hemispheres into the skull from which a brain had

been removed, and the other hemisphere into another such skull, and that

both transplants should take, and it may well be practically possible to do

so. [ … ] If these transplants took, clearly each of the resulting persons would

behave to some extent like P 1 , and indeed both would probably have some

of the apparent memories of P 1 . Each of the resulting persons would then be

good candidates for being P 1 . After all, if one of P 1 ’ s hemispheres had been

destroyed and the other remained intact and untransplanted, and the resulting

person continued to behave and make memory claims somewhat like those

of P 1 , we would have had little hesitation in declaring that person to be P 1 .

The same applies, whichever hemisphere was preserved [ … ]. But if it is, that

other person will be just as good a candidate for being P 1 . [ … ] But [ … ] that

cannot be – since the two persons are not identical with each other. (Shoemaker

and Swinburne, 15)

P1. A 1 and A 2 are two distinct persons.

P2. At t 2 > t 1 , A 1 and A 2 are such that each of A 1 and A 2 share exactly the

same amount of the X that A had at t 1 .

P3. X is the decisive factor for personal identity (e.g., body mass, brain

mass, memories, character traces), that is, for any persons A 1 and A 2 and

any times t 1 and t 2 , if A 2 has at t 2 most of the X that A 1 had at t 1 , then

A 1 and A 2 are the same person (assumption for reductio ).

C1. A 1 is the same person as A ( modus ponens , P3, P2).

C2. A 2 is the same person as A ( modus ponens , P3, P2).

P4. If X is the same person as Y, then Y is the same person as X (symmetry

of identity).

C3. A is the same person as A 2 ( modus ponens , P4, C2).

P5. If A 1 is the same person as A and A is the same person as A 2 , then A

is the same person as A 2 (transitivity, C1, C3).

C4. A 1 is the same person as A 2 ( modus ponens , conjunction, P5, C1,

C3).

C5. No such X can be the decisive factor for personal identity ( reductio ,

P1 – C4).

22

The Ship of Theseus

Ludger Jansen

Hobbes , Thomas . “ De corpore , ” in The English Works of Thomas Hobbes ,

Vol. 1 , edited by Sir William Molesworth . London : John Bohn , 1839 .

Plato . Phaedo , in Five Dialogues , 2nd edn. , translated by G. M. A. Grube,

revised by J. M. Cooper, 93 – 154 . Indianapolis : Hackett , 2002 .

Plutarch . “ Life of Theseus , ” in Lives , translated by Bernadotte Perrin, vol.

I , 1 – 87 . Cambridge, MA : Harvard University Press , 1967 .

The “ Ship of Theseus ” is an intriguing puzzle about identity through time.

It is based on the custom of the Athenians to send Theseus ’ ship each year

on a sacred voyage to Delos, because it was believed that Apollo once saved

the lives of Theseus and his fourteen fellow - travellers. The ritual was annually

repeated for a long time, and hence the ship needed continual repair,

new planks being substituted for the old ones. Plutarch relates to us that

already the Athenian philosophers had discussed whether the ship is still

the same ship although it consists, after a while, entirely of new planks

(Plutarch, “ Life of Theseus ” § 22 – 3; cf., Plato, Phaedo 58a – c). Hobbes put

a sophisticated twist to the story: Suppose, he said, that someone collected

the old planks and put them together again in the end, thus restoring the

old ship. The same ship, then, seems to exist twice, which is absurd. Hobbes

used this argument to support his version of relative identity: the original

ship T1 and the restored ship T2 share the same matter, whereas the original

ship and the repaired ship T3 share the same form.

Just the Arguments: 100 of the Most Important Arguments in Western Philosophy,

First Edition. Edited by Michael Bruce and Steven Barbone.