Psychological Continuity and the Problem of Fission

Recap of Psychological Continuity Views

• The General Schema of Psychological Continuity: The broad framework for these views states that an individual $X$ at time $t_1$ is identical to an individual $Y$ at time $t_2$ exactly when $X$ and $Y$ are psychologically continuous.
• Defining "Psychology": Within this philosophical context, an agent's psychology is defined as a collection of their mental states, specifically their attitudes. These include:
  • Beliefs
  • Desires
  • Intentions
• The First-Run View (Exact Psychology): An early, overly strict interpretation of psychological continuity suggests that two agents are continuous if they possess exactly the same mental states across time.
• Critique of the First-Run View: This view is considered "hopeless" and akin to a strict physicalist view that requires identical atoms and molecules for identity. It fails because human mental states change constantly. For example, a student’s beliefs about where the lecturer is standing change from the beginning of a class to the end, yet the student remains the same person.

The Causal Continuity View

• The Causal Criterion: This view attempts to improve upon the first-run view by leaning on the notion of causation. It posits that individual $X$ is identical to individual $Y$ if $X$ played an important causal role in $Y$ having the specific psychology that they do. In essence, if $X$ is responsible for the formation of the beliefs, desires, and intentions of $Y$, identity is preserved.
• The "Right Way" Qualification: For identity to hold, the causation must occur in the "right way." Philosophers must bracket "deviant causal chains." For example, a lecturer's psychology plays a causal role in a student's psychology by inducing new beliefs, but this does not make the lecturer identical to the student. Only specific, internal causal relations are deemed relevant to identity, though the exact definition of the "right way" remains a point of philosophical debate (a known lacuna in the theory).
• Predictions of Causal Continuity:
  • Childhood to Adulthood: It predicts that a seven-year-old version of an individual is identical to their present adult self because the child’s psychology played an essential causal role in the adult's psychology.
  • Animalism Contrast: Unlike animalism, it does not necessarily predict that an adult is identical to the three-month-old fetus that grew into them, as a fetus may lack the prerequisite psychology (mental attitudes) required for personhood.
  • Survival of Biological Death: This view is compatible with surviving biological death (e.g., body destruction via a "mincer" or "shredder"). Identity can persist as long as a previous version of an individual plays the correct causal role in the formation of a future individual's psychology, regardless of the physical medium.

Hypothetical and Sci-Fi Case Studies for Causal Continuity

• Hemispherectomy: This is a real medical procedure where half of the brain is removed. Neuroscience shows that functions from the removed hemisphere often migrate to the remaining one, allowing the person to lead a similar life. The causal continuity view predicts identity is preserved because there is a causal psychological relation between the pre-operation and post-operation entity, unhindered by the loss of physical brain matter.
• Brain Scanning and Replacement: If a diseased brain is scanned and a healthy one is grown and implanted, the view predicts identity is preserved. The pre-operation psychology caused the post-operation psychology via the intermediary scan.
• Silicon Uploading: If brain information is uploaded to a silicon neural net and the physical brain is replaced by this net, the view suggests identity is preserved. The physical substratum (biological vs. silicon) is irrelevant; only the persistence of beliefs and desires matters.
• Hard Drive Migration: Even if an entire persona is migrated to a hard drive, the view theoretically allows for identity to be preserved, provided the psychological states are causal descendants of the original organism.

Derek Parfit and the Teletransporter Thought Experiment

• Origins: The scenario comes from Derek Parfit’s famous book, Reasons in Persons. Parfit is noted for his work in personal identity, free will, and population ethics.
• The Scenario:
  • An agent enters a teletransporter on Earth to go to Mars.
  • The scanner on Earth records the exact state of all the agent’s cells (creating a blueprint) and then destroys the original brain and body.
  • This information is transmitted via radio at the speed of light to Mars (taking three minutes).
  • A replicator on Mars creates a new brain and body out of new matter based on the transmitted blueprint.
  • The agent wakes up on Mars with the same psychology, memories, and even minor physical details (like a shaving cut).
• Judgment: Intuitively, it seems the person survives and is identical to the one who entered the booth. The causal continuity view supports this because the pre-teleportation entity caused the post-teleportation entity.

The Problem of Fission Cases

• Definition of Fission: Fission is a process where one entity splits into two or more. It poses a fundamental challenge to identity views based on psychological continuity.
• Example Scenarios:
  • Dividing two brain hemispheres and placing each into a separate person ($B$ and $C$).
  • Scanning a brain once but using the data to create two identical replicates in different bodies.
• The Logic of the Problem: All fission cases share a structure where individual $A$ at time $t_1$ splits into individuals $B$ and $C$ at time $t_2$.
• Logical Principles:
  • Transitivity: If $X$ is identical to $Y$ and $Y$ is identical to $Z$, then $X$ is identical to $Z$.
  • Symmetry: If $X$ is identical to $Y$, then $Y$ is identical to $X$.
• The Derivation of Contradiction:
  1. Assume $A \text{ (at } t_1) = B \text{ (at } t_2)$ based on causal continuity.
  2. Assume $A \text{ (at } t_1) = C \text{ (at } t_2)$ based on causal continuity.
  3. Assume $B \text{ (at } t_2) \neq C \text{ (at } t_2)$ because they are two distinct people in different locations.
  4. By Symmetry, if $A = B$, then $B = A$.
  5. By Transitivity, if $B = A$ and $A = C$, then $B = C$.
  6. Result: We have derived both $B = C$ and $B \neq C$, which is a logical contradiction.

The No Competitors View

• Revised Identity Condition: To resolve the fission problem, some philosophers (like Cohen) argue that causal continuity is a necessary but not sufficient condition. They add a second condition: excluding competitors.
• Definition: Individual $X$ at time $t_1$ is identical to individual $Y$ at time $t_2$ if:
  1. $X$'s psychology caused $Y$'s psychology in the right way.
  2. $Y$ is the only individual at $t_2$ that satisfies condition 1.
• Prediction in Fission: In a case where $A$ splits into $B$ and $C$, neither $B$ nor $C$ is identical to $A$ because they "compete" with each other. Identity is destroyed by the presence of another candidate.
• Counterintuitive Consequences: This view implies that identity depends on external factors. For example:
  • If half of your brain is put in a donor body and the other half destroyed, you survive.
  • If half of your brain is put in a donor body and the other half is also put in a donor body, you cease to exist.
  • The existence of a "competitor" thousands of miles away determines whether you are currently identical to a future self.

Parfit’s Conclusion: Identity vs. Psychological Continuity

• The Exhaustion of Logical Space: In fission, there are only three options: (1) $A$ is both $B$ and $C$ (incoherent), (2) $A$ is neither (weird/external dependency), or (3) $A$ is exactly one (arbitrary).
• Identity Doesn't Matter: Derek Parfit concludes that since our concept of identity fails in these hard cases, identity itself is not what truly matters.
• What Matters is Psychological Continuity: Even if you are not strictly identical to your fission children, you should care about them because they are psychologically continuous with you. This informs ethical and practical behavior (e.g., you should still save money for your fission children even if you aren't "them").

Questions & Discussion

• Question about Vagueness: A student asked about how big a causal role is required for identity and if mixing psychologies (e.g., part of person $A$ and part of person $B$ merged) results in identity.
  • Response: The lecturer noted that the view might be inherently vague. The requirement for a "robust" causal role isn't fully defined, and it might be indeterminate whether one survives in such mixed cases.
• Question about Animalism and Fetuses: A student asked what an animalist would say about a fetus that splits early in development (twins).
  • Response: Animalism handles fission more easily because it relies on biological organismic identity. However, it requires a clear criterion for when an organism begins. If one organism becomes two, the animalist would likely say the original organism persists as one, or that identity only starts after the split. The lecturer conceded that defining a "neo-organism" vs. a full organism is a complex biological hurdle for the animalist.
• Question on the Lecturer's Personal Opinion: A student asked the lecturer what they believe the "self" is, given that all theories presented have significant loopholes.
  • Response: The lecturer stated they are a "vessel for information" and avoid personal opinions, emphasizing that the goal of philosophy is to highlight how difficult it is to reconcile our robust intuitions with consistent theories. The lecturer admitted they might find the loss of identity in fission cases "upsetting" personally.