Informal Proof
Based on the proof by John Geanakoplos of Cowles Foundation, Yale University published by Economic Theory (journal) in 2005. (An attempt to improve upon it appeared on the same journal in 2012.)
We wish to prove that any social choice system respecting unrestricted domain, unanimity, and independence of irrelevant alternatives (IIA) is a dictatorship.
Read more about this topic: Arrow's Impossibility Theorem
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