VATICAN CITY, JAN. 16, 2009 ( Sunday begins the Week of Prayer for Christian Unity, which will end with a celebration of vespers led by Benedict XVI.

The Vatican announced that the Holy Father will preside at this prayer service at 5:30 p.m. on Jan. 25, the Feast of the Conversion of St. Paul, in the Basilica of St. Paul Outside the Walls.

The Week of Prayer for Christian Unity is traditionally celebrated Jan. 18-25 in the northern hemisphere, though in the south there is some variation on the dates. This year's theme is "That they may become one in your hand (Ezek 37, 17)."

The Pontifical Council for Promoting Christian Unity stated that this theme, as well as those chosen for each day of prayer, is "rooted in the experience of the Churches in Korea."

The council explained that "in their context of national division the Churches have turned for inspiration to the prophet Ezekiel, who also lived in a tragically divided nation and longed for the unity of his people."

The council worked with the Commission on Faith and Order of the World Council of Churches for the preparation of materials for the week of prayer.

The themes for each day of the week are:

Jan. 18: Christian communities face to face with old and new divisions.

Jan. 19: Christians face to face with war and violence.
Jan. 20: Christians face to face with economic injustice and poverty.

Jan. 21: Christians face to face with ecological crisis.
Jan. 22: Christians face to face with discrimination and social prejudice.
Jan. 23: Christians face to face with disease and suffering.

Jan. 24: Christians face to face with a plurality of religions.
Jan. 25: Christian proclamation of hope in a world of separation.

Several bishops' conferences offer additional resources on their Web sites. On the Irish conference site, a video of Bishop Anthony Farquhar, chairman of the Episcopal Commission on Ecumenism, explains the meaning of the week.

He encourages listeners to follow Christ's commandment to "pray that all may be one," without forgetting the second part: "so that the world may believe that we are sent." He added, "As we try to come closer to Jesus, then I think we are in fact going to come closer to each other."

The prelate continued, "We all have the opportunity of helping by committing ourselves to ecumenism on all levels, all the way through the international level, the national one, the diocesan one, or the ordinary social one where people are breaking down prejudices, barriers or suspicions -- maybe just through a purely social context. Then it is for each one of us to say: 'There is a level where I can make a contribution.'"

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On the Net:

Vatican resources for the Week of Prayer for Christian Unity and throughout 2009:

Irish bishops' conference resources:

U.S. bishops' conference resources: