Some teachings, such as, "Love your neighbor" or, "Care for your community," are shared by almost every religious or ethical practice. From an evolutionary standpoint, that makes sense: In the long run, the group does better than the individual. But welcoming strangers, let alone caring for them, does not come naturally. I was reminded recently that our brains aren't wired for it. Strangers are, by definition, unknown. The unknown often generates fear. Strangers, in this context, are harmful.