PHILOSOPHY 100
(Ted Stolze)
Notes on James Rachels,
Problems Philosophy
Chapter Five: The Problem of
Personal Identity
What is a Thought Experiment?
“A thought experiment is an imaginary scenario that’s used to
help concentrate the mind on certain key factors in . . .
reasoning. The basic principles of thought experiments are
the same as those for actual scientific experiments: isolate
the variables to be tested; see how individually altering these
factors effects the result; the draw general conclusions about
the significance of these variables. In contrast with scientific
experiments, of course, the significance of thought
experiments in . . . philosophy will be [philosophical] . . . rather
than physical.”
(From Julian Baggini and Peter S. Fosl, The Ethics Toolkit: A
Compendium of Ethical Concepts and Methods [Malden, MA:
Blackwell, 2007], p. 199.)
The Duplicator Thought Experiment
Two Aspects of Personhood
• At a Moment
• Over Time
Two Theories of
Personhood at a Moment
• The Soul Theory
• The Bundle Theory
The Soul Theory
“Within each person is a kernel that may be
called the soul or the ego or the self. It is the
subject of all the person’s experiences. It is
simple and indivisible. And it is present
throughout the person’s life” (p. 57).
The Bundle Theory
“[T]he parade of mental items is all that exists, as
far as the ‘mind’ is concerned” (p. 57).
A New Version of the Bundle Theory:
The Connectome
Professor Sebastian Seung’s TED Talk on
“I am My Connectome”:
http://www.ted.com/talks/sebastian_seung.html
What is a Connectome?
In his book Connectome: How the Brain’s Wiring Makes Us Who We Are
(New York: Mariner Books, 2013 [2012]) Sebastian Seung (professor of
computational neuroscience at MIT) has defined a connectome as “the totality
of connections between the neurons in a nervous system” (p. xiii). Seung
argues that each of us has a unique connectome and that “minds differ
because connectomes differ” (p. xiv). Finally, he distinguishes two senses of
the self: the connectome from neural activity: “Since the connectome defines
the pathways along which neural activity can flow, we might regard it as the
streambed of consciousness. The metaphor is a powerful one. Over a long
period of time, in the same way that the water of the stream slowly shapes the
bed, neural activity changes the connectome. The two notions of self—as
both the fast-moving, ever-changing stream and the more stable but slowly
transformed streambed—are thus inextricably linked” (p. xix).
Two Senses of
Personhood over Time
• Qualitative
• Numerical
Two Theories of
Personal Identity over Time
•
Same-Body (Same-Brain)
•
Same-Memory (Memory-Links)
The Same-Body Theory
“X, who exists at an earlier time, and Y, who exists
at a later time, are the same person (numerically) if
and only if they have the same body” (p. 61).
Objections to
the Same-Body Theory
•
The Ship of Theseus thought experiment
•
The Prince and the Cobbler thought
experiment
•
Variations involving gender, age, species, etc.
The Same-Brain Theory
“X, who exists at an earlier time, and Y, who
exists at a later time, are the same person
(numerically) if and only if they have the same
brain” (p. 63).
The Memory Theory
“X, who lived at an earlier time, is the same person
(numerically) as Y, who lives at a later time, if and
only if Y can remember doing what X did, feeling
what X felt, thinking what X thought, and so on” (p.
60).
An Objection to the Memory Theory
•
Forgetting and amnesia
•
A Case Study: Clive Wearing
(http://www.liveleak.com/view?i=5a9_1261557
924)
The Memory-Links Theory
“X, who lived at an earlier time, is the same
person (numerically) as Y, who lives at a later
time, if and only if a chain of memories links X
and Y” (p. 60)
Another Objection to
the Memory (and Memory-Links)
Theory
• Apparent vs. real memories