AGAINST PERSONAL IDENTITY
Parfit: the question: “will I be the same
person tomorrow” has no meaningful
answer.
The argument summarized:
1. Either dualism (“Ego Theory”) or else
psychological continuity (“Bundle
Theory”) are the correct theories of
identity.
2. Dualism is false.
3. The Bundle Theory is incompatible with
survival.
4. Therefore, personal survival is a myth.
1
Against dualism: Split brain cases
Hemispheres of S’s brain have been
severed:
 S observes a two-coloured screen.
 Left eye sees red; right eye blue.
S is asked: (1) how many colours do you
see? (2) What colour do you see?
 Right hand writes: (1) “One”. (2) Red.
 Left hand writes: (1) “One”. (2) Blue.
Parfit: This shows that there are two
streams of consciousness in one body.
 If dualism were true, the soul would
unite the streams into one
consciousness.
Dualism must be false.
2
Objection
There is only one stream of consciousness:
the subdominant hemisphere is not
conscious but is subordinated to the
dominant one.
Parfit: People have had their dominant
hemispheres destroyed.
 They are changed but can still talk,
move, respond and generally interact.
So, subdominant hemisphere is conscious.
So, there can be disunified streams of
consciousness.
 This contradicts the idea of a unified
soul.
 Bundle theory is the only way to go.
3
Implications of the bundle theory
Teleportation:
 You are scanned at T1 in S1.
 You are destroyed.
 A replica is created at T2 in S1.
Bundle theory: You survive because
psychological continuity is preserved (in the
right, causal way).
Parfit: What if two copies are made?
 They can’t both be identical to you (2 ≠
1).
Conclusion: since each duplicate is
psychologically continuous with you,
psychological continuity is not sufficient for
preserving identity
4
Against the No-Branching Clause
Suppose that you are beamed somewhere.
 You open your eyes, look around, recall
the teleportation and your childhood,
and then get on with your mission.
 According to the Bundle Theory, you
survive.
If, however, 10 duplicates were to be
teleported to the same room, none would be
you.
 How can such an extrinsic fact be what
determines whether you survive?
5
Summary
On the Bundle Theory, there are only the
following kinds of fact:
 Experiences exist.
 Some are psychologically continuous.
But psychological continuity relates sets of
experience that are not strictly identical.
So this is possible:
B
C
D
E
A
Neither B, C, D nor E is identical to A.
But if we remove B, D, and E, that can’t
suddenly make C identical to A.
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Operations
Teleportation is like an operation where
each of your cells is replaced by a duplicate.
 The above reasoning shows that
100% replacement destroys identity.
But do you believe that, for example, 0.1%
replacement does not destroy identity?
If so, then you believe that:
 There is some critical percentage
between 0.1% and 100% that marks
the boundary between survival and
death.
Parfit: It is absurd to suppose there is a line
at which removing one cell would destroy
your identity, but not removing that cell
would preserve it.
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Impossible to find
Parfit: What’s more, we could never detect
where such a line would be.
 Say the crucial percentage is 49%.
 If 50% is replaced, you die.
 But the 50% replacement is
psychologically continuous with you.
 So, we could never determine that
s/he isn’t you.
Conclusion: We should give up belief in
such a line.
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We are only bundles
Parfit: If the bundle theory is true, then there
is no point trying to find this line.
 There is no “you”, no Ego/substance
that underlies your experiences.
 There are only the experiences.
Here is a complete description:
1. John has 50% of his cells replaced.
2. Psychological continuity is preserved.
3. The continuity has an unusual cause.
If we feel the need to ask: “But is the result
really identical to John?”
 Then we have ignored the lessons of
the bundle theory:
 There is no further fact of the matter
besides 1-3
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A short way of looking at it
B1: 100% replacement destroys identity.
B2: 0.1% replacement preserves identity.
B1 + B2 = critical percentage = absurd.
But B1 is proven by branching cases.
So, must give up B2.
10
Lessons of the Bundle Theory
Suppose Q (at T1) and P (at T2) are
psychologically continuous experiences.
Q: Are P and Q part of the same person?
Parfit: What are you asking?
1. Same soul? No: dualism is false.
2. Strict identity (P = Q)? No: Leibniz’s
Law.
3. Psych. Cont.? Yes.
But: #3 may apply to many distinct bundles
of experience: R (at T2), S (at T2), etc. may
all be psychologically continuous with Q.
Okay, but which one is really identical to Q?
Parfit: senseless question: no more facts
other than 1-3.
11
Surprising conclusion
1. You and your replica are psych. cont. but
not identical.
2. Your experiences today and tomorrow
are psych. cont.
Therefore:
3. Future, psychologically continuous
experiences are no more “you” than is
your replica.
In other words:
 There is no connection between “you”
today “you” tomorrow that is not shared
by you and possibly many distant
replicas.
Since there is no survival in the latter case,
there is none in the former.
12
Final view: Dualism
There are two questions to ask:
1. Conceptual: What is it for P2 at T2 to be
identical to P1 at T1?
2. Evidential: On what grounds do we
conclude P2 = P1?
Swinburne: Most writers assume that the
answer to #2 gives us the answer to #1.
 These are “empiricist theories” of
personal identity.
 They are not satisfactory.
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The story of empiricism
1. BODILY THEORY
 Problem: Body gains/loses parts.
2. PSYCHOLOGICAL CONTINUITY
 Problem: Teleportation/Duplication.
3. BRAIN THEORY
 Problem: Brains can be duplicated as
well.
4. PARFIT: There is no (total) survival.
 Problem: How does Parfit know this?
 It could be that one part of the brain is
the centre of experience (Chisholm).
 Parfit’s view needs empirical support
that he doesn’t provide.
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Response
Swinburne:
 Bodily continuity
 Brain continuity
 Psychological continuity
Are all (fallible) evidence of personal
identity.
 However, what they are evidence of is
distinct from these criteria.
 Personal identity  the criteria we use to
ascribe personal identity.
Okay, but then what is personal identity?
15
The story of dualism
Swinburne: Logic alone can’t tell us which
set of future experiences I will have.
 That’s why the empiricist theories have
so many counterexamples.
Perhaps as a matter of fact I will have one
and only one set of future experiences
(even in teleportation cases).
 There may be empirical doubt as to
which of a future duplicate is in fact me.
 But it doesn’t follow that there is no fact
of the matter.
16
The mind-body relation
For a body to be my body means:
1. I can move this body directly.
 I don’t need to do something else first in
order to get my arm to move.
2. Empirical knowledge is gained through
the body.
 What I know about the world is the
result of the world’s effects on this body.
In short: this body is my vehicle of agency in
the world and knowledge of the world.
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Minds are not bodies
But then, it is entirely possible that I find
myself:
1. Able to move another body directly.
2. Gaining information via another body.
It is also coherent to suppose a person
becomes disembodied:
 Able to move objects in a room directly
(not through a body).
 Able to know where objects in a room
are without seeing them.
Disembodied survival is logically coherent:
Minds are not necessarily bodies.
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Against verificationism
Swinburne: Body/brain continuity is our
main evidence of personal identity.
 So: I can’t describe an actual case
where memory and bodily continuity are
lost but identity remains.
But: only verificationists conclude that lack
of evidence = lack of possibility.
So, it remains logically possible that I
survive without my body and without my
memories.
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The argument for dualism
1. Let:
 P = I am conscious and exist in 2003.
 Q = my body is destroyed in 2003 (end)
 R = I have a soul in 2003
 S = I exist in 2004
2. Whatever else is true today, it is logically
possible that P & Q & S.
 (I.e. (x)(P&Q&S&x), where x ranges
over states consistent with P&Q)
3. but if ~R, then (P & Q & S) is not
possible.
 (I.e. ~(P&Q&S&~R))
Therefore:
4. R
 (I.e., ~R is not within the range of x)
20
The essence of persons
So, the form (essential properties) of a
person is:
 The ability to have conscious
experiences and perform intentional
actions.
But what is it for such an essence at T2 to
be identical to one at T1?
Swinburne:
 If S2 at T2 has the same form (thought,
intention) as that as S1 at T1.
 And S2 is made out of the same stuff as
S1.
 Then S2 = S1.
(Generalized Aristotelian criteria).
21
Mind-body dualism
It follows that we are made up of two kinds
of stuff. A person is:
 A thinking thing (soul) combined with
 A physical body.
What matters for survival is the continuation
of the soul.
Souls are not divisible:
 All matter takes up space so all matter
can be divided (logically) into smaller
volumes.
 Souls take up no space so there is no
sense in which they can divide.
So, strict identity is preserved.
22
Problems with Dualism
According to dualism one’s body, beliefs
even personality may change. However:
One survives because the soul continues.
But:
 If the soul is not my beliefs, personality
or body, what exactly is it? What’s left
to be “me”?
 Is there room in a scientific worldview
for an immaterial soul?
 How can an immaterial substance
interact with a material one?
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Problems with the argument
Assume (P & Q & S) is possible.
 It doesn’t follow that this is only possible
if I in fact have a soul.
 What follows is that this is only possible
if it is possible that I have a soul.
All Swinburne has shown is that I might
have a soul, not that I do.
2. Swinburne assumes that whatever else is
true of me, it is possible that I continue to
exist without my body.
 Why assume this?
 If ~R is true of me right now, then it may
not be possible that I continue w/o my
body.
 So the possibility of (P & Q & S)
assumes I have a soul, it doesn’t prove
it.
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Appendix: survival and the A-/B-series
debate
Two views on identity:
Endurance: A person is wholly present at
each moment s/he exists. The person
endures by remaining unchanged from
moment to moment (like dualism).
Perdurance: A person is extended in time,
composed of temporal parts or stages.
These parts are related so as to be
united into a single whole. There is no
one part that is wholly present at all
times in a person’s life.
Does one’s stance on the A-/B-series
dispute constrain one’s position here?
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Temporal parts and the A-series
Argument 1: perdurance is inconsistent with
A-time.
1. If X is composed of temporal parts,
then there is no time at which all of X’s
parts are present.
2. I.e., X can’t be wholly present at
different times.
3. So, X can’t “move” in time for this
requires all of X to be at T1, then all of
X to be at T2, etc.
Therefore:
4. If the perdurance view is right, a
person can’t “move” through time and
the A-series must be false.
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Objections
Objection 1: The perduring whole is present
so long as any temporal part is present.
 I.e., when part P1 is present, the person
is (wholly) P1; when P2 is present, the
person is (wholly) P2.
Reply: Then there is not one thing
persisting in time, but two things: P1 and
P2.
Objection 2: perhaps each part successively
becomes present.
Reply: then the person is never wholly
present at any time, only a part is.
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Objection 3: Why not say that I am wholly
present so long as part of me is.
 E.g. W.W.II. is present if one of it’s
battles is; John is present if one of his
parts is.
 Then, as different parts become
present, I (wholly) move in time
Reply: If part of me is in room A and part in
room B, I am not wholly in either.
 So, why say that John (or the war) is?
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Rejoinder: Because time differs from space.
If one temporal part is present, we have to
say the whole is present—the alternative is
absurd:
 If the whole is past, then no parts are
present. If it is future, then no parts are
present.
 So, if a part is present, the whole is
neither past nor future.
 So, it is present if one part is.
Reply: This proves too much, i.e. it proves
that a whole is past if one part is past:
 If W is future, no parts are past.
 If W is present, no parts are past.
 So, if part is past, then whole is past.
Upshot:
 If perdurance view is right, must adopt
the B-series view.
 To hold to the A-series, one must adopt
the endurance view.
But …
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Can the B-theorist be an endurantist?
Argument 2: No, she can’t.
1. Assume B-series
2. S is (tenselessly) P
3. S is (tenselessly) not-P
4. So S is P and not-P, which is absurd.
Therefore,
5. B-series requires temporal parts to
exhibit the different properties.
Reply: S is (tenselessly) P at T1 and not-P
at T2.
 I.e. properties are relations if the
substance view is right.
 This is consistent with B-series.
So, the B-series is consistent with both
endurance and perdurance. The A-series
can only have endurance.
Is this an advantage for the B-series view
(i.e., it rules out less)?
30
Relational vs. substantive time
Relational time: time is sets of events
standing in temporal relations to each other.
Substantive time: time is a substance that
contains events.
Argument: substance view + B-series view
= substantive time.
 Assume B-time.
 Assume S is an enduring substance.
 For all time, S first thinks of Plato (event
P) then Descartes (event D).
 Assume nothing else exists.
 I.e. all history contains is P followed by
D.
Every occurrence of P (or D) has exactly the
same temporal relations to everything else.
So, there is no way to differentiate them.
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Reply 1: Each is present at a different time.
Problems:
 Abandons B-series for A-series
 Assumes A-properties occur at different
times, and this time might be
substantive (i.e. how differentiate
them?).
Reply 2: Each subsequent P-type event is
part of a different stage of S.
 I.e. we individuate P’s by reference to
parts of S.
Problem: we have abandoned the
endurance view for perdurance.
Conclusion: we need substantive time to
differentiate the different P (D) events.
 In other words, different P’s (D’s) are at
different substantive points in time.
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But there is an objection to this:
Maybe the story, as told, is incorrect:
 In fact, there are only two events, P then
D (and one substance, S).
 Since we can’t distinguish them, it
follows that we weren’t describing a
universe of recurring P’s and D’s.
 Rather, we were actually describing a
universe in which S thinks of P then D,
and that’s it.
 There is no need for substantive time for
there are no P’s (D’s) to distinguish.
So, relationalism is saved: it is consistent
with B-time and endurance (we just need to
carefully interpret our stories).
But this isn’t the end of the story …
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Eternal recurrence
It may be false, but eternal recurrence
seems possible.
 I.e., there could be a world in which P
and D repeat infinitely.
So, if we assume S is a substance, and time
is tenseless, we must assume:
 Time is substantive.
That is the only way to make sense of
different P’s preceding different D’s.
I.e., so long as eternal recurrence is
possible:
 The substance view of persons + B-time
Entail:
 Time is a substance.
Is this a weakness of the B-series view?
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