Arrow's theorem

Etymology
Named after economist Kenneth Arrow, who demonstrated the theorem in his doctoral thesis and popularized it in his 1951 book Social Choice and Individual Values.

Proper noun

 * 1)  A theorem stating that no voting system can be perfectly fair in all circumstances. Specifically, when voters have three or more distinct alternatives, no ranked voting electoral system can convert the ranked preferences of individuals into a community-wide (complete and transitive) ranking while also meeting the specified set of criteria: unrestricted domain, non-dictatorship, Pareto efficiency, and independence of irrelevant alternatives.