Parfit's Hitchhiker
Updated 2026-08-01
INTRODUCTION
English translation pending.
CORE DEFINITION
Parfit's Hitchhiker is a thought experiment by the philosopher Derek Parfit. Stranded in a desert, you ask a passing driver for a lift and promise to pay him once you reach town. Both of you are rational, and the driver knows that after arriving you will have no reason to pay. Anticipating this, he refuses and you die. The example shows that a commitment made before the payoff can be defeated by rational defection after it, so a credible commitment device, or a reputation for stubborn honesty, can itself be the rational move.
SCAFFOLDING EFFECT
Reduce cognitive load
- Post-hoc check: ask what you will want to do once the other side has already delivered. - Commit early: bind yourself with escrow, contract, or reputation before the payoff arrives. - Redesign payoffs: arrange incentives so that honoring the deal stays optimal afterwards.
Anchor fast decisions
Cooperation requires the other side to believe you will pay when paying no longer benefits you. Because your future self will optimize its own position, a bare promise carries no force. A visible constraint, a deposit, a hostage, or a costly reputation converts an empty promise into a credible one, which is what allows the trade to happen at all.
MINIMUM ACTION
In progress 0/1Practice this model in one real situation:
account_treeGenealogyexpand_more
menu_bookReferencesexpand_more
Source support: Explicit
- lesserwrong.comhttp://lesserwrong.com/w/parfits_hitchhikerverified
PRIVATE NOTES · Only visible to you
SAVED Q&A
ENTRY Q&A · Private saving available
Ask with a clear boundary
thinkingmodels answers from published entry context only.
Your question is sent to thinkingmodels. The answer uses public entry context only.
RELATED MODELS