“People who live by the same code are rendered mutually predictable to one another. They act in keeping with each other’s expectations and desires. They can cooperate. They can even compete peacefully, because everyone knows what to expect from everyone else. A shared belief system, partly psychological, partly acted out, simplifies everyone—in their own eyes, and in the eyes of others. Shared beliefs simplify the world, as well, because people who know what to expect from one another can act together to tame the world.”