It was a quick line in a mobile-game commercial, visible for less than a second before the advert moved to touting how much fun the game was. It showed pixel peasants crying for the player’s help. “Help! Outsiders,” they said. I do not think there is anything that sums up everything that is wrong in the world better than this line.

The player was tasked with protecting ancient Rome from the evil barbarian outsiders. The reason the outsiders were evil is baked into their name, barbarians. These people were different than the Romans, and that was reason enough to fight them.

To be clear, this is not limited to Romans. The word barbarian is actually Greek for anyone who does not speak Greek, which oddly makes the Romans barbarians by definition. The Arabs call non-Arabs, especially Persians, “Ajam”; the Jews called non-Jews “Gentiles or Goys”; and Slavic people called non-Slavs, especially Germans, “Nemets” for mutes. I can go on but you get the picture. Everyone has their own special way of saying “these people are not like us;” and therein lies the problem.

Let us start with the obvious problems this line of thinking creates. Donald Trump made his now (in)famous line about building a wall to keep Mexicans out [because they are not like us]. Europe had mixed reactions to Syrian refugees but the negative ones can be summed up as “[Country] for [Country’s people]”, like Marine Le Pen’s “France for the French” or Viktor Orbán’s “Hungary for the Hungarians” [because the refugees are not like us].

Nothing helps establish who “We” are better than “Not them.” The ancient Greeks started to think of themselves as a unit only after they fought the Persians. The people of the Italian peninsula became true Romans only after they fought the Carthaginians. The Spanish kingdoms united mainly to banish the Muslim Emirate of Granada. The US added the clause “One nation under God” to the pledge of allegiance only when faced with the Atheist Communists. You can expect Europe to become “more European” and the US to become “more American” in the face of immigration. This “more” will be defined more as the opposite of whatever the immigrants are seen to be than a continuation of the current state of affairs.

Of course, this “Us vs. Them” way of thinking goes even deeper into the fabric of the same nation. The mess that is Iraq/Syria is caused in no small part by “These Sunnis/Shiites/Kurds/etc are not like us,” (though the main cause is still the economy). These factions will find more things that are different about each other the longer the conflict goes on because, again, nothing establishes an identity better than “Not them.”

The first step towards global peace (because the term “World Peace” sounds too cliché) is to recognize that “They” have as much right to live in peace and prosperity as “Us.” Only then will we realize we are not all that different afterall.