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_1261557924)

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