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Harsanyi's Purification Theorem

Game Theory

Harsanyi's Purification Theorem shows that a mixed-strategy Nash equilibrium of a game of complete information can be understood as the limit of pure-strategy equilibria of nearby games in which each player has private information about slightly perturbed payoffs. Named for John Harsanyi, it addresses the interpretive puzzle of how players could deliberately randomize by showing mixed strategies can instead arise from small amounts of unmodeled private information.

Facts
Statement
A mixed strategy Nash equilibrium can emerge even though each player plays a pure strategy, so long as players have incomplete information about the payoffs of their opponents. 1
Proof Year
1973 1
Classification
Statement Form
Existence Theorem 1
Connections

Has Statement Form

Entity-backed identity for the statement-form enum value this theorem already carries, resolved to a mathematics concept by an explicit value-to-entity map (phase 3 bucket conversion, docs\design_entity_backed_browse_buckets_20260928.md). The statement-form fact itself stays on the theorem unchanged.

In Branch

Source Purification theorem - Wikipedia
Sources
1. Purification theorem - Wikipedia
  • Lead section
    The purification theorem shows how such mixed strategy equilibria can emerge even if each player plays a pure strategy, so long as players have incomplete information about the payoffs of their opponents.
  • Lead section, first sentence
    In game theory, the purification theorem was contributed by Nobel laureate John Harsanyi in 1973.
  • In Branch: Game Theory, Lead sentence
    In game theory, the purification theorem was contributed by Nobel laureate John Harsanyi in 1973.
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