PHI 001: Introduction to Philosophy
Introduction to Philosophy
PHI 001: Introduction to
Philosophy
The Self and Identity Through Time
A Personal Identity Game
Staying Alive
Identity: Numerical v. Qualitative
Qualitative Identity = Exact Similarity
Numerical Identity = Being One and the
Same Thing As
Identity: Numerical v. Qualitative
A B
Are A and B exactly similar?
Are A and B one and the same thing?
Identity: Numerical v. Qualitative
A B
Are A and B exactly similar?
Are A and B one and the same thing?
The Indiscernibility of Identicals
(Uncontroversial)
For any thing x and any thing y, if x is numerically
identical to y, then any property that x has y also
has, and any property that y has x also has –
i.e., then x and y have exactly the same
properties.
Contrapositive (Equivalent): If there is a property
that x has but y lacks, or a property that y has
but x lacks, then x is not numerically identical to
y.
Indiscernibility of Identicals
As a slogan: “Having exactly the same
properties is necessary for numerical
identity.”
Indiscernibility of Identicals
Obama has the property being over six feet
tall.
Gilmore does not have that property.
So Obama and Gilmore are not numerically
identical.
Identity of Indiscernibles
(Controversial)
For any thing x and any thing y, if x and y
have exactly the same properties, then x
and y are numerically identical.
Slogan: “Having exactly the same properties
is sufficient for numerical identity.”
Personal Identity
What is the question?
(Q1) How can we tell whether a person x,
existing at one time, is numerically the
same as some person y, existing at a
different time?
Personal Identity
What is the question?
(Q1) How can we tell whether a person x,
existing at one time, is numerically the
same as some person y, existing at a
different time?
No. This is epistemology.
Personal Identity
What is the question?
(Q2) What makes it the case that a person x
existing at one time is numerically identical with
a person y existing at a different time.
When doing metaphysics, we want a theory to
specify the grounds of personal identity over
time, not merely to give us a reliable to guide
that lets us find out when it holds.
Personal Identity
What do we want from a theory of personal identity over
time? In other words, what is the question that a theory
of personal identity over time is supposed to answer?
Necessarily, for any x and y, and times t and t*, if x is a
person and exists at t, and y exists at t*, then x = y if and
only if ___________________________.
We want a theory of personal identity to fill in the blank in a
way that makes the resulting statement both true and
informative. (To avoid circularity, what fills in the blank
must not presuppose an understanding of the concept of
personal identity over time.)
Personal Identity
The Matter Theory
• Necessarily, if x is a person existing at t
and y exists at t*, x=y if and only if the
matter that x is made of at t is the same
matter as the matter that y is made of at
t*.
Is being made of the same matter really
sufficient for personal identity? Is it
really necessary?
The Matter Theory
Case 1: The anti-matter gun. Let Person1 be the
person who exists at t1 and is composed at t1 of
parcel of matter M. A split second after t1, the
anti-matter gun annihilates the matter that
composed the tip of Person1’s left pinky
fingernail. Let Person2 be the person who exists
(in roughly the same place as Person1 was
located at t1) shortly after the anti-matter gun is
applied. Person2 is composed at t2 of parcel of
matter M*. Parcel of matter M is not the same as
parcel of matter M* (they merely overlap).
The Matter Theory
Argument A against the matter theory
1. If the matter theory is true, then Person1
is not numerically identical to Person2.
2. Person1 is numerically identical to
Person2.
--------------------
3. The matter theory is not true.
The Matter Theory
Argument A, if successful, shows that
sameness of constituent matter is not
necessary ???
sufficient ???
for personal identity over time.
The Matter Theory
Argument A, if successful, shows that
sameness of constituent matter is not
necessary
for personal identity over time.
The Matter Theory
Case 2. Oratorious, the famed Roman statesman,
is composed at t1 of matter M. He dies, his
corpse rots, and M is scattered all over Earth.
Two thousand years later, by wild coincidence,
M has once again taken the form a person,
George U. Bush: Bush is composed of M at t2.
Aside from the odd fact that he is made of M,
there does not appear to be anything unusual
about his history: records indicate that he
developed from a 7 pound infant born in 1943.
The Matter Theory
Argument B against the matter theory
1. If the matter theory is true, then Oratorius
is numerically identical with George U.
Bush.
2. Oratorious is not numerically identical
with George U. Bush.
---------------------------
3. The matter theory is not true.
The Matter Theory
Argument B, if successful, shows that
sameness of constituent matter is not
necessary ???
sufficient ???
for personal identity over time.
The Matter Theory
Argument B, if successful, shows that
sameness of constituent matter is not
sufficient
for personal identity over time.
Personal Identity
The Soul Theory
• Necessarily, if x is a person existing at t
and y exists at t*, x=y if and only if the soul
that x has at t is the same as the soul that
y has at t*.
Personal Identity
What is a soul? To count as a soul (as philosophers use the term), a
thing
• must be immaterial / non-physical / not made of matter,
• must be capable of causing things to happen, and be capable of
being causally affected by other things,
• must be conscious or play some essential role in giving rise to
consciousness, and
• must be a substance (a thing, like a rock or a ghost) rather than an
event (something that happens or occurs, like an explosion or a
basketball game) .