Reasons and Persons
Reasons and Persons (1984) by Derek Parfit examines personal identity, rationality, and morality — and argues that standard self-interested rational-choice assumptions break down under scrutiny.
Core Idea
Parfit contends that personal identity is not what matters in survival (psychological continuity is), which reshapes how we weigh our future selves and our obligations to future people. He exposes paradoxes in self-interest theory and population ethics — most famously the “Repugnant Conclusion” — and pushes toward more impersonal reasons.
Why It Matters for Critical Thinking
A model of rigorous thought-experiment reasoning: Parfit shows how carefully constructed cases can overturn intuitions we assumed were bedrock, including the assumption that rational choice means maximizing self-interest.