1. Personal Identity

2. Homework
• Bring in a baby photo of yourself to next
Wednesday’s lesson (you’ll find out why
later…)

3. • Are you the same person you were 5 seconds
ago?
• How do you know?

4. • Are you the same person you were last night?
• How do you know?

5. • Are you the same person you were last year?
• How do you know?

6. • Are you the same person you were when you
were 11?
• How do you know?

7. • Are you the same person you were when you
were 3?
• How do you know?

8. • Are you the same person you were when you
were a baby?
• How do you know?

9. What secures our personal identity
through time?
• What makes you the same person throughout
your life?
• How do you know the answer to this
question?
• How do other people know that you are the
same person on a daily basis?

10. What is the problem of personal identity?
• Why is identity important: personal identity is
an important issue in philosophy of mind
because philosophers want to establish what
it is that makes a person the ‘same’ person
over a period of time. They are not interested
in identity in the sense of how we see
ourselves – that might be a psychological
issue.

11. What secures our personal identity
through time?
When philosophers talk about Identity they
usually mean strict identity – an all-or-nothing
relationship. Either identity holds, or it doesn’t.
Identity to the philosopher doesn’t just mean
similarity of qualities, or even identity of
qualities. In fact, though, the philosophical
understanding of identity is even more precise
than this.

12. Qualitative versus Numerical Identity
1. In your groups, you need to sort the cards
(sorry, you’ll have to cut them out first!) into
two categories – things which are
qualitatively identical and things which are
numerically identical.
2. Next, you need to define, as a group, the two
terms and the distinction between them.

13. Approaches to Identity
• Philosophers are interested in two types
of identity: qualitative identity concerns
things that are identical in type – such as
identical things.
• Numerical identity concerns things that
are single entities, but have qualities that
make us refer to them in distinct ways.
• Superman and Clark Kent are numerically
identical but are regarded as two
separate beings.
• Philosophers are most concerned with
the metaphysical issues of personal
identity, not the epistemological issues.
• It’s not how we know that people are
identical to themselves, but what the
nature of that identity is.

14. Qualitative versus Numerical Identity
Qualitative Identity – holds in the case e.g. of identical toothbrushes, or
other manufactured goods. These things exactly resemble each other – you
can’t tell them apart. But they are separate entities – they can exist
independently of each other.
Numerical identity is different to qualitative identity. It’s the sort of identity
that holds where there is only one of a thing that is that thing. Numerically
identical things are always the same thing even if we sometimes think of
them as being different (e.g. the morning star and the evening star are both
Venus.) The total number of entities is 1, and so they can’t exist
independently of each other – even if they look different over time.
Philosophers are usually interested in numerical identity when considering
personal identity. How can someone be the same at both t=0 and t=1 even if
lots about them is different? What are the necessary and sufficient
conditions for people to be the same at t=0 and t=1? The key question for
Personal Identity is: How can a present person be the same as a past
person?

15. Two Reductionist Approaches
• Philosophers usually reduce personal identity to one of two basic
elements, although most accounts of what we are would have to
take account of both.
• The two elements are, of course, the mind and the body.
• Physical continuity argues that we identify individuals by the fact
that they are physically the same being as they were on previous
occasions.
• Psychological continuity is the view that it is the continuation of our
mental life by memory we identifies us as the same person.
• A number of questions arise from these two approaches. For
example: How do we judge physical continuity? How can we argue
that someone’s mental life continues if they suffer severe brain
damage?

16. 3rd person versus 1st person perspectives –
physical versus psychological approaches
There are usually thought to be two ways of approaching the
question of personal identity – the first-person approach, and
the third-person approach.
• The third-person approach uses the idea that physical
continuity over time is the right criterion to use for
personal identity. So: is physical continuity through
observation (in practice or in principle) a criterion for
personal identity? Is the 3rd-person perspective sufficient
to prove identity?
• There is also a first-person perspective which is non-
observational. You know – or think you know – that you
are the same person that you were last week. You feel you
have psychological continuity because you have a strong
sense of the continuity of your mental life.

17. Physical Continuity
In the physical continuity theory a person
is judged to be the same person only if
they have the same body that they did
yesterday.
That is, we are ‘identical’ to ourselves on
the basis of our physical characteristics.
This would be a fairly commonsensical
approach: we know that our friends and
family are indeed the people we think they
are because they resemble them physically.
What problems might arise if we did not
recognise a person as the same physical
being that we knew before?

18. Problems with Physical Continuity
• However, physical continuity can be seriously
problematised when someone’s body changes
over time.
• Think about the aging process or plastic surgery.
Are we the ‘same’ physically as we were when
we were five? Would we be the ‘same’ if we had
a drastic nose job?
• In some cases physical changes are so large that
we can’t identify the person as the ‘same’ on the
basis of physical appearance.
• More serious problems occur with issues such as
cloning. If a clone is exactly identical to its
original in a physical way, is it the ‘same’? We
would have to argue both yes and no.
• A clone is the same in the sense of being an
exact copy but not in being numerically the
same.

19. The Prince and the Cobbler
• John Locke raised an important problem for
physical continuity theory by distinguishing
the man and the person.
• A man for Locke is a physical human being.
However, a person is the same social and
psychological being.
• Locke developed this distinction by using
the example of the prince and the cobbler.
• Locke imagines a prince and a cobbler who
have had a complete exchange of
personalities or ‘ a transfer of souls’.
• Would the prince continue to be the same
person if he suddenly had the mind of
someone else?
• Most people would say that the answer to
this question would be no. For this reason,
Locke completely rejects physical continuity
as an argument for personal identity.

20. Sydney Shoemaker
Sydney Shoemaker updated Locke’s
example by considering the possibility
of brain transplants.
Imagine a brain transplant between
two people.
If one patient died during the
transplant, who would the survivor be?
Would he be the person whose body he
had or the person whose mind he had?
Shoemaker rejects the idea that the
body would form the simple basis of
our identity because the behaviour and
habits of that person would be
governed by the mind of someone else.

21. Psychological Continuity
• John Locke argued that real identity
is found in psychological continuity,
not the physical continuity of the
body.
• Personal identity for Locke is a
matter of the continuity of
consciousness from one moment to
another.
• As such, identity is not a matter of
the physical substance of the person,
but rather the consciousness that
unites the person’s different actions.
• The mind of a person is the thing that
really ‘underpins’ who they are for
Locke, and it is this mind that makes
the different connections between
their different and varied
experiences.

22. Locke and Memory
• The key to Locke’s account of
psychological continuity is
memory.
• For Locke, a person is the ‘same’
person over time if they have the
same ‘reservoir’ of memories.
• A person may change physical
from childhood onwards, but if
they have the same basic memory
structure then they are the ‘same’
person.
• What problems can arise if
memory is the criteria for
psychological continuity?

23. Problems with Psychological Continuity
John Locke’s argument also seems to be
commonsensical, but is open to a number
of serious problems.
The most obvious is that the mind can
change as drastically as the body. As we
age our minds can fail as well as our bodies
and memory loss would not obviously
mean that we are not the ‘same’ person.
If we suffered traumatic memory loss as
the result of an accident would we become
someone else?
These problems mean that Locke’s account
of psychological continuity is not as
plausible as it may at first seem.

24. Thomas Reid
Thomas Reid developed an objection to Locke using the
example of the ‘brave ensign’.
Reid imagines an ensign (a young soldier) who stole
apples as a young boy and was flogged for it.
The boy grew up to become a brave soldier who won
many medals, but still remembered stealing the apples
and his violent punishment.
Many years later the ensign was an old general with a
distinguished military career.
The old general had clear memories of his youth and the
battles in which he won his medals.
However, the old general has absolutely no memory of
being the boy who stole apples, and even his flogging
has vanished from his mind.
For Reid, this example clearly shows that on Locke’s
account of personal identity the general is not the same
person as the boy.
However, this seems to be absurd since most people
would argue that the two clearly are the same person.

25. Joseph Butler
Joseph Butler added the further criticism
that Locke’s account of identity is circular.
Butler’s argument is that remembering an
event does not constitute identity, since
consciousness is the very thing that
constitutes identity in the first place.
This is circular because we are already
presupposing that identity exists for us to
have a memory of it.
For the ensign to remember his problem
with the apples means that there was
already some formation of his identity at
the earlier stage.
The fact of the memory does not add
anything to this and so a collection of
memories is not the same as a person’s
identity.

26. Examples of Identity Problems
• Plastic Surgery.
• Transformations.
• Loss of memory.
• Multiple Personality Disorder.
• Psychoses – schizophrenia.
• Fiction – e.g. Dr. Jeckyll and Mr. Hyde.

27. Plenary
What secures our personal identity through
time?
• Whether either physical or psychological
continuity through time are necessary or
sufficient conditions of identity.