Ship of Theseus
Ship of Theseus
Also known as: Theseus's Paradox
Overview
The Ship of Theseus is an ancient philosophical thought experiment that explores the nature of identity over time. If every part of a ship is gradually replaced with identical materials, is it still the same ship? And if the original parts are reassembled elsewhere, which is the real Ship of Theseus?
Purpose
To question what it means for an object—or even a person—to remain the same over time despite change. It challenges our understanding of persistence, continuity, and essence.
Key Question
When all components of an object are replaced, does its identity remain? What defines the "real" object: continuity of function, structure, material, or something else?
Example
Your body replaces its cells over years. Are you still the same person? If your memories and personality were uploaded to a machine, would that be you?
Interpretations
- Mereological Essentialism: An object is not the same if any part is replaced.
- Four-dimensionalism: Identity includes time as a dimension—objects are time-bound entities.
- Psychological continuity (for persons): Identity persists through memory and consciousness.
Source
First recorded by Plutarch in Life of Theseus; discussed by Hobbes and Locke in modern philosophy.