While the religious experts focused on clarifying boundaries, Jesus focused on what lies at the center.

Why do Christians, who are called to be holy, settle for being weird?

In his commentary on Romans, British scholar James D. G. Dunn noted that in the apostle Paul's day, an inordinate amount of rabbinic writing focused on three aspects of the law: circumcision, Sabbath keeping, and dietary regulations. That is odd. No devout first-century rabbi would have said that these areas were the heart of the law. The heart of the law was clear: "Hear, O Israel: The Lord our God is one Lord; and you shall love the Lord your God with all your heart, and with all your soul, and with all your might" (Deut. 6:4-5). So why the remarkable emphasis on circumcision, Sabbath keeping, and eating habits?

To explain this, Dunn refers to what sociologists might call boundary markers. Boundary markers are highly visible, relatively superficial practices that serve to distinguish people inside a group from those outside. So if you pull up next to a 1960s VW van plastered with peace signs and bumper stickers that read "Make love, not war," navigated by a driver with long hair, granny glasses, and love beads, you know with whom you are dealing.

If on the other side is a BMW piloted by a hair-moussing, Rolex-wearing, Brie-tasting, chardonnay-sipping 30-year-old, you know his group as well.

Religious groups, perhaps even more than other kinds, tend to want to distinguish themselves from outsiders. So the religious experts of Paul's day spent a great deal of time focusing on boundaries. These practices received the lion's share of attention—not because they were so important in themselves, but because they became litmus tests for determining who was ...