Philip Jones Griffiths/Magnum Photos

PEACE, said W. B. Yeats, comes dropping slow.

After 15 years, the Good Friday peace agreement in Northern Ireland still occasionally quivers, sometimes abruptly, and yet it holds. It is one of the great stories of the second half of the 20th century, and by the nature of its refusal to topple, it is one of the continuing marvels of the 21st as well. While rockets fizzle across the Israeli border, and funeral chants sound along the streets of Aleppo in Syria, and drones cut coordinates in the blue over Kandahar, Afghanistan, the Irish peace process reaffirms the possibility that — despite the weight of evidence against human nature — we are all still capable of small moments of resurrection, no matter where we happen to be.

This is the Easter narrative: that the stone can be rolled away from the cave.

Hundred of years of arterial bitterness, in Ireland and elsewhere, are never easy to ignore. They cannot be whisked away with a series of signatures. It takes time and struggle to maintain even the remotest sense of calm. Peace is indeed harder than war, and its constant fragility is part of its beauty. A bullet need happen only once, but for peace to work we need to be reminded of its existence again and again and again.

On Easter Saturday 15 years ago, George Mitchell, the United States envoy for Northern Ireland and former senator from Maine, descended the steps of the Stormont Hotel and slid into the back seat of a waiting car to drive to Belfast airport. He was going home, leaving behind the prospect of peace for a people who had only ever known the maelstrom of its undoing.

The agreement had taken two years of negotiations. It had come close to collapse on several occasions. There had been scores of trans-Atlantic trips. Endless hotel room stays. All sorts of semantical shuffling. But now the documents were signed. The peace belonged to a people who would affirm it, or not. Mr. Mitchell, and his team of negotiators, were well aware that the verdict would belong to history. Indeed, there would come more bombings. Shootings. Further rancor. But there were also, on the horizon, referendums and handshakes and the astonishment of the impossible.

It’s a universal story: every culture has known it at one time or another. The desire for peace asserts itself as the most basic human right. In Havana, Colombian diplomats have spent the last several months in hopes of an agreement with the Marxist rebel movement FARC. In Mali, the government has made overtures to Tuareg rebels following the French intervention. President Obama’s recent visit to Israel not only created new hope for talks with Palestinians but also helped end a spat between Turkey and Israel.

The true art of peace, negotiators know, lies in our ability to deal with the mighty weapon of language.

Mr. Mitchell’s great skill was that he learned to embrace silence. He sat at his table, listening to speech after speech. He soon found out that perhaps no other culture in the world has as many skilled and loquacious loudmouths as Ireland, north and south. (The old joke goes that Irish people with Alzheimer’s forget everything except the grudge.) He pitched himself against the tenacity of the fanatics.

He was unpaid and initially unheralded, but he fell in love with the people and allowed them to talk through their vitriol. He tried never to take sides — he split a feather down the middle and encouraged both halves to take flight.

Then he struck. With language again. Early in 1998, he and his committee insisted that an agreement be reached by Good Friday. Mr. Mitchell and the negotiators had chosen Easter for its symbolic content. But there was another reason as well — Mr. Mitchell, 64 at the time, wanted to get home to his wife and infant son. Sixty-one children were born in Northern Ireland on the day six months earlier that his son, Andrew, was born in New York: now there were 62 reasons to secure a peace.

The date was set. Mr. Mitchell and his team bore down on it. He convened meetings. He consulted world leaders — after all, the process had been kick-started by President Clinton. He spent time with Prime Ministers Tony Blair of Britain and Bertie Ahern of Ireland and a group of British and Northern Irish leaders that included John Hume, David Trimble, Mo Mowlam, Gerry Adams and Martin McGuinness. He kept listening. He tolerated death threats. He pleaded. He cajoled. And even after the agreement was signed, he understood that only history would bring it home.

By COLUM McCANN