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Personal Identity Theories

Aug 28, 2025

Overview

This lecture explores the philosophical problem of personal identity: what makes a person the same over time, focusing on the Body Theory and Memory Theory.

The Problem of Personal Identity

  • Personal identity questions whether a person remains the same "self" throughout life despite physical and psychological changes.
  • Popular culture, like Doctor Who, illustrates how identity is challenged by changing bodies and personalities.

Body Theory of Personal Identity

  • Body Theory claims you are the same person as long as you have the same physical body.
  • The body's physical matter changes constantly through processes like cell replacement, questioning if physical continuity is enough for identity.
  • Thought experiments highlight issues: how much physical change can occur before you're a new person?

Memory Theory of Personal Identity

  • John Locke's Memory Theory states identity persists through connected memories and consciousness rather than bodily continuity.
  • Memories link different stages of your life, creating a chain of personal identity.
  • Problems arise: people do not remember being born, and dementia can break memory continuity.
  • False or inaccurate memories further complicate if they count toward personal identity.

Importance of Personal Identity

  • Personal identity underpins social obligations, moral responsibility, and expectations (e.g., promises, paychecks).
  • If identity does not persist, moral and social commitments lose their foundation.

Key Terms & Definitions

  • Personal Identity — The philosophical problem of what makes someone the same person over time.
  • Body Theory — The view that you remain the same as long as you have the same physical body.
  • Memory Theory — Locke’s idea that identity persists through a connected chain of memories.
  • Consciousness — Awareness of oneself, often linked to memory and identity.

Action Items / Next Steps

  • Consider which theory of personal identity (body or memory) you find more convincing and why.
  • Prepare for the next lecture on whether a persistent personal identity is necessary.