Quote Originally Posted by wm View Post
Recognition of someone as a fellow Prussian engenders trust. How? Is it merely artifactual or is it necessary? If it is necessary, what is the causal nexus?
I would say it is largely artefactual, a remnant of of a brain that was only designed to be a member of a small group (less than 100 members). In modern society where there are thousands of people you can interact with you need a shorthand to know who to trust.

Check out "less than human: Why we Demean, Enslave, and Exterminate Others".

Also, along the same lines: "Extreme mass Homicide: From military massacre to genocide." A good read along the us-versus-them line of thought.