“A watershed moment.” If you’ve ever heard that phrase, you probably already know that it refers to a decisively important, history-changing event. But what is a “watershed”? Mignon Fogarty, better known on the Internet as “Grammar Girl,” helps clear the matter up.

It has nothing to do with sheds.

In American English, a watershed is a basin or area of land that, well, sheds water, as when the runoff from rain or snowmelt flows downhill into a stream or river. In British usage, however, the word has a slightly different meaning: it refers to a high point in the landscape, like a ridge, around which the water flows into different basins on opposite sides of the ridge. Metaphorically, then, a watershed is an event that divides history. Before the event, things are one way, and after, things are quite different.

Thank you, Grammar Girl.

Why mention this? Because Acts 15 and the council in Jerusalem is a watershed moment in the book of Acts.

From the very beginning of Luke’s narrative, we have been watching the gospel spread outward from Jerusalem to the “ends of the earth” (Acts 1:8, NRSV), just as Jesus predicted. But with that evangelistic movement, the young church has experienced growing pains.

Paul’s missionary activity, in particular, confronted the church with a core identity issue. As the number of Gentile converts grew, the original believers in Jerusalem, all Jewish, were forced to face difficult questions. How can our former enemies — God’s enemies! — become our brothers and sisters? Is it really possible, is it even permissible, to form one family out of all of us together?

To be honest, as a modern-day middle-class American, it’s difficult for me to identify with the urgency of the first-century Jew vs. Gentile distinction. But similar divides have always plagued the church. There is an “us,” and there is a “them,” an in-group and an out-group, defined by ethnic, racial, social, or political lines. And the question created by the radical movement of God’s grace in the book of Acts and beyond is, What does it mean to accept “them” as part of “us”?

As we’ve seen, even with the life-altering experience of watching the Holy Spirit come upon a Roman centurion named Cornelius and all those in his household, Peter hadn’t quite made the transition from “us vs. them” to just “us” (again, see Gal 2:11-21). He was wishy-washy toward the Gentile believers in Antioch, earning him a public rebuke from Paul. To his credit, however, Peter was willing to be corrected; testifying before the Jerusalem council, he reminded everyone of the story of Cornelius and argued strongly that circumcision should not be forced on Gentile converts.

Acts 15 is a watershed in Luke’s story because it represents an official proclamation from Jerusalem, given in the Spirit by the apostles and the elders of the church: Gentile believers are to be accepted as part of the family, without circumcision. After this point in the story, Peter, having given his full support to the Gentile mission, vanishes from the pages of Acts. The narrative follows Paul, and Jerusalem is no longer the geographical center of the action.

We will take a more careful look at the council’s decision in upcoming posts. But for now, I want us to not miss the significance of the moment. For those of us who are “Gentiles” — if Romans 11 is any indication — it’s far too easy to take for granted our place in the story of salvation, just as previously, the Jews had taken their place for granted. Something like this is always going to be a temptation when we engage in us vs. them thinking.

So here’s the question: who is your “them”?