A global human society that would be both peaceful and prosperous is not that hard imagine. We have real life instances of codes that many people in many lands can understand, and by and large follow, in many sectors of our lives already. Think of how universal the sign that forbids smoking is.  

Think of how universal the mores of automobile driving have become. Yes, there are cities in which I would be afraid to drive, but even then, there would only be some parts of those cities that would be too hectic for me and only at times of heavy traffic congestion. Yes, there are some major driving laws and mores followed in one group of cultures that are not followed in others. But the differences are only a few, and customs like, for example, driving on the left-hand side of the road are not that hard to get used to. A few hours to get accustomed to the change, and then the odd mistake that you quickly catch yourself making. I've experienced this exact adjustment when I went to New Zealand. 

And there are so many driving mores that coincide. Don't cut other people off when changing lanes. Follow at a safe distance. Don't pass over a solid center line. And so on. Even many road signs are universal. 

For the most part, people drive cars to get from one location to another more quickly than they could if they were walking. A few of the drivers on the road are simply driving around to fill up their idle time, but such a practice, in the first place, costs too much (gas is fairly expensive everywhere) and in the second place, puts pollutants into the atmosphere for no good reason whatsoever. But, in short, we're there because of practical, widely-shared reasons.  

My point is that when people all must share a resource, in the driving case, the highways system of that country, they can readily work out a set of regulations that everyone is expected to obey when using that shared resource because it is in the interest of all of them to do so. Sometimes, you're in a hurry. But you don't drive through crowded streets like a maniac because it is contrary to your own interests over the long haul to do so. You'll very like get a ticket or get in an accident, and then whatever you were rushing to will really have to wait. And you might even get killed. Definitely, not a desirable outcome. 

Emergency vehicles like fire trucks and ambulances can race through city streets when going to a fire or other emergency, but they must turn on their sirens when doing so. The system, most of the time, works, and even the exceptions to the normal driving customs can be accommodated. 

This metaphor is telling us in unequivocal terms that if we could come up with a basic set of values and mores on which the large majority of people on earth could agree, we really could live together in prosperity and peace, and even preserve the ecosystems of our planet while doing so. The earth is our most precious common resource. We can learn to live together on it. And the kids who grew up after the mores fell into place would occasionally wonder, "What was so hard about just simply making sense." Cultural codes, once they are in place, seem as automatic as breathing.  

One day, a teacher in a school somewhere in the world will be working on a history project with a class made up of all kinds of students. The students will be looking at old forms that students back in the twentieth century had to fill out at school. They will find a space on one form which reads: "Racial/Ethnic Origin". A child will say to the teacher, "What was this for?" and the teacher will say, "I don't know." 

We just have to believe.