Martin Luther King at the Lincoln Memorial

Two hundred and fifty thousand people stand before the Lincoln Memorial on August 28, 1963, and the march that has brought them here is, at its core, a church meeting.

The civil rights movement is soaked in the Black church — its songs, its rhetoric, its organizing structure, its theology. The leaders who stand at the podium are almost all ordained ministers. The marchers who have walked from Selma and Birmingham and Montgomery have been sustained by congregations that prayed and sang and fed them. The movement's idiom is the idiom of scripture — Exodus, Isaiah, the Sermon on the Mount — applied with precision to the specific injustice of American segregation.

Martin Luther King Jr. comes to the podium last. He has a prepared speech. He delivers most of it. And then Mahalia Jackson, standing nearby, calls out: Tell them about the dream, Martin.

He puts the papers down.

I have a dream that one day this nation will rise up and live out the true meaning of its creed: We hold these truths to be self-evident, that all men are created equal.

I have a dream that my four little children will one day live in a nation where they will not be judged by the color of their skin but by the content of their character.

The speech lasts seventeen minutes. It draws on Amos and Isaiah and the spirituals and the Declaration of Independence and the Constitution and the Gettysburg Address. It is the most consequential sermon in American history.

King's dream is Isaiah's dream — the vision of the prophet who saw valleys lifted and mountains made low and the glory of God revealed to all flesh simultaneously.

He applied an eight-century-old vision to a specific American injustice with such precision that two hundred and fifty thousand people recognized it as true. Not as poetry — as description. As the way things are supposed to be and are not yet.

The prophetic tradition has always done this: taken the ancient vision and aimed it at the present failure. Not as comfort but as indictment. Not as reassurance but as demand.

The dream is still unrealized. The vision is still ahead. The church that carries it is still called to aim it at the specific gap between what is and what should be.

What is the specific valley in your world that needs lifting? And who is the Isaiah you are waiting for — or are you it?