Arrow's impossibility theorem

"To put it another way, if we assume everybody should count equally, then there is no method of voting which will avoid some possibility of violating the rules."

"Contrary to the rationalist followers of the American economist Kenneth Arrow, for whom the instability of majority rule was a problem, Dahl’s Madisonian insight was that instability is actually an advantage. It keeps majorities fluid in ways that stop politics from becoming winner-take-all contests in which losers might as well reach for their guns."

"Arrow’s Impossibility Theorem is quite surprising. It shows that three very plausible and desirable features of a social decision mechanism are inconsistent with democracy: there is no “perfect” way to make social decisions. There is no perfect way to “aggregate” individual preferences to make one social preference. If we want to find a way to aggregate individual preferences to form social preferences, we will have to give up one of the properties of a social decision mechanism described in Arrow’s theorem."