Psychological studies suggest that the mere fact of division, even when there is no substantive content to it, can be corrosive: in a series of experiments in the 1950s and ’60s, groups of similar people arbitrarily divided into subgroups quickly exploded into conflicts of “Lord of the Flies”-like intensity. Other studies have shown that when relatively like-minded people are grouped together, they don’t settle around the average point of view of the individuals in the group but rather become more extreme in the direction toward which they’re already inclined.