A quick study of the viral-like growth of Protestantism after the Reformation makes one things agonizingly obvious: nothing divides Christians more quickly or fiercely than familiarity. Small differences in practices, subtle translation preferences, and genuine theological disagreements severed similar Christians into antagonistic opponents. And it’s not just Christians who are doing this. In the past decade we have become acutely aware of the deep, often deadly divides between Shiite and Sunni Muslims. But in the first century the deep divide between Jews and Gentiles was not nearly as rancorous as were the animosities that simmered between the Jews and their “kissing cousins,” the Samaritans.

That long-established lack of love between Jews and Samaritans is the underlying landscape of t…