Electing a Pope

After the Athenians, Catholic scholars were among the first to analyze problems of voting (what is today called social choice theory).  The potential for chaotic elections was certainly familar to the Cardinals who after many disputes over who should be Pope settled on the current two-thirds rule for election in 1179.  And while I wouldn't go so far as  Pope Pius II  who in 1458 said (after his own election (of course!) "What is done by two thirds of the sacred college, that is surely of the Holy Ghost, which may not be resisted," it is interesting to note that 2/3rds does have a number of special stability properties (see the difficult paper of Saari here and the earlier link).

For more on the history and practice of Papal elections you can listen to two free historical lectures from The Teaching Company.