COWLES FOUNDATION FOR RESEARCH IN
ECONOMICS Box 208281
COWLES FOUNDATION DISCUSSION PAPER NO. 1123R Two Brief Proofs of Arrow's Impossibility Theorem John Geanakoplos April 1996 The first proof shows that Arrow's axioms guarantee neutrality: every social choice must be made in exactly the same way, which quickly leads to dictatorship. The second proof clarifies the last step, and also confirms the intimate connection between Arrow's Impossibility Theorem and the Condorcet triple. The second proof shows that a doubly pivotal agent must be a dictator; the Condorcet triple guarantees the existence of a doubly pivotal agent. Neutrality guarantees the existence of a (symmetrically) doubly pivotal agent. |
