Personal Identity - Derek Parfit Summary
Chapter 1: What is Personal Identity?
Conceptual Scenario
Consider a hypothetical situation:
Serena and Venus are having lunch together, each in her own chair for an hour.
However, they switch places, bodies, and memories every five minutes.
Questioning the nature of this scenario:
Is this scenario plausible in terms of personal identity according to Swinburne?
Is there anything inconsistent or absurd in this story?
Despite not addressing this specific epistemological question, Swinburne may have insights on this scenario.
Context of the Discussion
The excerpt from Personal Identity (1984) by Swinburne introduces the debate surrounding personal identity, engaging in a discussion with Sydney Shoemaker, who shares a similar theory with Derek Parfit (1942–2017).
Parfit, a Fellow Emeritus in Philosophy at All Souls College, University of Oxford, authored notable works including Reasons and Persons (1984) and On What Matters (2011).
Derek Parfit: Personal Identity
Introduction to Teletransportation
Parfit enters a Teletransporter to travel to Mars:
Previous journeys took weeks; this machine operates at light speed.
Pressing the green button means losing consciousness and waking up moments later, with about an hour of unconsciousness.
Mechanism of Teletransportation described:
TheScanner destroys the brain and body while recording detailed cellular states.
Information transmitted to the Replicator on Mars, which constructs a new body similar to the original.
Emotional tension arises regarding the process:
Initially nervous about Teletransportation, reassured by his wife who has experienced it without consequence.
Narrative Development
Post-teleportation observations:
Parfit finds no change in the new body; physical injuries, like a cut, remain.
A new scenario with the New Scanner:
This scanner records without damaging the original brain or body but crucially, poses a health risk of cardiac failure on Earth.
Further elaboration compares perspectives on identity in Teletransportation:
Simplistic view: The Replica is seen as 'me.'
Alternative view: pressing the button equates to death, and the Replication merely creates a new person, despite similarity in experiences.
Teletransportation and Branch-Line Case
Parfit delineates between two types of identity:
Qualitative Identity: two people (e.g., him and his Replica) appearing similar.
Numerical Identity: the notion that they are one and the same individual.
Discussion of fading identity through the Branch-Line Case:
While they can interact, their experiences diverge fundamentally.
Considering outcomes: If one feels pain or dies, the other does not share this experience, asserting distinct identities.
Major philosophical argument:
Challenges the concept of surviving death through cloning or replication processes.
Question posed regarding the value of 'being me' in various forms of identity continuation.
Concept of Personal Identity
Parfit presents his arguments on personal identity over time:
Nature of a person.
Conditions for being the same person at different times.
Features necessary for continued existence through time.
The Physical Criterion
Definition:
The criteria determining personal identity:
Continued existence of sufficient parts of the brain to constitute a living person.
Rejection of Teletransportation as travel, asserting it represents death due to loss of original identity.
Example: Individuals on life support but not dependent on entirely intact bodies still possess identity as their psychological continuity remains intact despite physical changes.
The Psychological Criterion
Adopted views regarding psychological continuity:
Contrasts pure mental entity or soul approach with memory continuity.
Amnesia case study:
Distinguishes between experience memories and factual ones.
Suggestion of revising Locke's view to incorporate overlapping memory chains, allowing for significant connections over time.
Identity & Memory Connection
Psychological connectedness and continuity defined:
Connectedness relates to direct psychological connections, while continuity deals with prolonged networks of these connections.
Assuredness of identity over time despite low levels of strong connections from past experiences.
What Happens When I Divide?
Exploring hypothetical identity scenarios within teletransportation and bodily fission complexities.
Examining situations with identical twins and critical surgery:
Contrasting expected identity versus actuality with psychological continuity.
Resolution of personal identity issues during possible divisions, with definitions and implications outlined.
Conclusion & Philosophical Implications
Distinguishes between personal identity as a conclusion versus relations of continuity that sustain value.
Evaluates personal identity concerns of survival, especially in cases of duplications.
Acknowledges the potential tension between Reductionist and Non-Reductionist perspectives on personal identity throughout situational examples, suggesting clarity over complex identity entanglements.
Further Reflection & Doubts
Parfit expresses confusion over the implications of the Reductionist view at a personal level:
Emphasizes fears rooted in the perception of personal identity.
Suggests ongoing debate over beliefs concerning identity, existence, and continuity in human experience.
Testing Understanding
Multiple-choice scenarios to discern between forms of numerical and qualitative identity, tying back to philosophical inquiries on existence and continuity.
Promotes reflective consideration of identity constructs outlined in prior contexts.
Chapter 1: What is Personal Identity?
Conceptual Scenario: The Serena and Venus Thought Experiment
The Hypothetical Setup:
Serena and Venus are seated in separate chairs for one hour.
Every five minutes, they undergo a total swap of local bodies, physiological structures, and mental memories.
This scenario forces a distinction between the "container" (the body) and the "content" (the mind/memory).
Philosophical Inquiry:
Swinburne uses such scenarios to go beyond mere empirical observation. He asks if this scenario is logically consistent or if it contains nested absurdities.
The core question: Even if the physical and psychological traits are perfectly swapped, is there a "further fact" or a non-physical soul that keeps Serena being Serena and Venus being Venus?
Swinburne's perspective often leans toward the idea that since we can conceive of this swap without logical contradiction, identity must be something more than just physical or psychological continuity.
Context of the Discussion: Swinburne vs. Parfit
Theoretical Framework: The discussion stems from Swinburne's Personal Identity (1984), written as a rebuttal to the empiricist/reductionist views shared by Sydney Shoemaker and Derek Parfit.
Derek Parfit's Radical Reductionism: Parfit (1942–2017) challenges the "Common Sense" view that identity is a deep, determinate fact. His works Reasons and Persons (1984) and On What Matters (2011) argue that identity is simply a matter of degree and is not what fundamentally matters for survival.
Derek Parfit’s Analysis of Personal Identity
The Teletransporter: Standard Case
The Mechanism: Parfit uses the Teletransporter to test our intuitions about what it means to "survive" death.
The Scanner: Records the exact state of every cell and molecule in your brain and body, destroying the original in the process.
The Replicator: Beams this information to Mars, where it constructs a new body out of new matter that is atom-for-atom identical to the original.
The Paradox of Experience: From the perspective of the person on Mars, the process is seamless. They wake up with all your memories, hopes, and character traits. To an observer, the person is the same, but the original physical substance is gone.
The New Scanner: The Branch-Line Case
Narrative Development: Parfit introduces a "New Scanner" that records data without destroying the original body.
The Scenario: The scanner works, and the Replica is created on Mars. However, the original Parfit remains on Earth. A technician informs the original Parfit that while the scan was successful, it caused a malfunction that will lead to his cardiac failure in one hour.
Competing Identities: If the Replica is "me," then I survive the death of my body on Earth. However, if numerical identity requires a one-to-one relationship (A = B), how can two distinct entities (the one on Earth and the one on Mars) both be the "same" person? This violation of the transitivity of identity suggests that identity cannot be the thing that matters in survival.
Qualitative vs. Numerical Identity
Qualitative Identity: Refers to sharing the same properties. Two identical billiard balls are qualitatively identical. The Replica on Mars is qualitatively identical to the original Parfit.
Numerical Identity: Refers to being one and the same individual. For example, the morning star and the evening star are numerically identical (both are Venus). Parfit argues that while we have qualitative continuity during teleportation, we lose numerical identity.
The Physical Criterion of Identity
Core Definition: This view posits that a person is the same over time if and only if there is a continued existence of enough of the physical brain to constitute a person.
Objections:
This view renders Teletransportation as "death" because the original atoms are replaced.
It struggles with "Ship of Theseus" style problems: if parts of the brain are replaced by silicon chips bit-by-bit, at what point does the original identity cease to exist?
The Psychological Criterion of Identity
Lockean Roots & Revision: Inspired by John Locke, this view focuses on consciousness and memory.
Psychological Connectedness vs. Continuity:
Connectedness: Direct psychological links (e.g., remembering what you did yesterday, or carrying out a plan formed five minutes ago).
Continuity: Overlapping chains of strong connectedness. You may not remember being an infant, but your toddler self did, and your adult self remembers being a toddler. This creates a transitive chain (Person A \rightarrow Person B \rightarrow Person C).
Quasi-Memories (q-memories): Parfit suggests we can have memories of experiences that we didn't physically experience ourselves (e.g., if a memory was recorded from one brain and played in another), which preserves the psychological link without requiring the same physical vessel.
The Fission Case: When Identity Divides
Hypothetical Fission: A person’s brain is divided, and each half is transplanted into a separate body. Both resulting people are psychologically continuous with the original.
Logic of the Outcome:
I do not survive: This seems wrong because I would have survived if only one half was transplanted.
I survive as one of the two: This is arbitrary; there is no reason to pick one over the other.
I survive as both: This is impossible for numerical identity (A \neq B and C simultaneously).
Parfit's Resolution: Survival (Relation R) is what actually matters, and it is a matter of degree. Identity is a "one-one" relation that we artificially impose on the "one-many" reality of psychological survival.
Conclusion: The Reductionist Perspective
Reductionism Defined: The belief that a person's existence just consists of the existence of a brain and body and the occurrence of a series of mental and physical events. There is no "further fact" or Cartesian ego.
Philosophical Implications: Parfit claims that accepting reductionism makes the prospect of death less terrifying. It shifts focus from the survival of a specific "ego" to the continuation of valuable psychological traits and connections across the human experience.
The overall conclusion of the notes focuses on Derek Parfit's Reductionist Perspective on personal identity. Parfit concludes that there is no "further fact" or a persistent "ego" that makes someone the same person over time; instead, a person’s existence consists solely of physical and mental events (the brain, body, and psychological continuity).
Key takeaways include:
Survival vs. Identity: Parfit argues that numerical identity (being exactly one and the same person) is not what matters. What actually matters for survival is Relation R—the psychological connectedness and continuity of memories, character, and intentions.
The Fission and Teletransportation Paradoxes: These scenarios suggest that identity is a "one-one" relation we impose on reality, but survival can be "one-many." In cases like fission, even if numerical identity fails (since one person cannot be two), survival is still achieved through psychological continuity.
Philosophical Release: By accepting that there is no deep, unchanging self, Parfit suggests that the prospect of death becomes less terrifying, as the focus shifts from the survival of a specific "soul" to the continuation of valuable psychological traits within the human experience.
Swinburne's Counter-Point: While Parfit leans toward reductionism, the notes also highlight Richard Swinburne's view that since we can conceive of identity swaps (like the Serena and Venus experiment) without logical contradiction, identity might involve a non-physical component or "further fact" not captured by purely physical or psychological data.