IN THE first century BC, the Roman historian Sallust wrote that the republic had descended into internal strife because of the destruction of its enemy, Carthage, in the Third Punic War. Fear of the enemy, or metus hostilis, produced domestic cohesion. Without an adversary, Romans turned their knives inward: “when the minds of the people were relieved of that dread [of Carthage], wantonness and arrogance naturally arose.”
Something similar may be happening today. There are numerous explanations for the current discord in the United States, ranging from globalization to the splintering of American communities. But one big factor is being largely ignored: the lack of a foreign threat. External threats can unify diverse populations. Psychologists have shown that people quickly form “in-groups” and “out-groups” (us versus them), whether it’s two sports teams going head-to-head or two nations at war. The desire for mutual protection, and sometimes for vengeance, can reduce enmity between in-group members and create a “one-for-all” mind-set.
A threatening rival can also reinforce a sense of national identity. The Harvard political theorist Karl Deutsch described a nation as “a group of people united by a mistaken view about the past and a hatred of their neighbors.” According to the political scientist Clinton Rossiter, “There is nothing like an enemy, or simply a neighbor seen as unpleasantly different in political values and social arrangements, to speed a nation along the course of self-identification or put it back on course whenever it strays.”
The role of foreign peril in cultivating a sense of national identity may be especially important in the United States. American self-identity is not based on an ancient shared heritage, but rather on a set of political ideals: the creed of individual rights and democracy. This is a fragile basis for unity in a continent-sized country populated by huddled masses from all over the world. The existence of the other may be essential to shore up American identity and reinforce a sense of political exceptionalism.