On April 11, 1963, Pope John XXIII released an encyclical that would change the face of Catholic social justice.

Pacem in Terris (Peace on Earth outlined the Roman Catholic Church's stance on peace and human rights.

Peace on Earth states that because all people are created in the image of God, all people are worthy of dignity, respect and basic human rights – including the right to worship and to organize.

And, John wrote, because these rights are divinely ordained, Catholics have a God-given duty to safeguard them.

On Tuesday, the Catholic Peacebuilding Network began a two-day conference celebrating the 50th anniversary of "Pacem in Terris" at the Catholic University of America in Washington, D.C.

"It is our hope that this event will advance peace building as a priority for the Catholic Church here in the United States," said Father William Headley, founding dean of the Joan B. Kroc School of Peace Studies at the University of San Diego, in the conference's opening statements.

"Also, our hope is that it will focus attention on ways in which the Catholic perspective on peace building can contribute to the wider opportunities and challenges for peace building in the U.S. foreign policy," he said.

The day began with Mass at the National Shrine of the Immaculate Conception, and the conference moved to the Pryzbyla Center.

Tuesday's topics included immigration, climate change and U.S foreign policy.

Speakers included representatives from the U.S. Conference of Catholic Bishops, the U.S. State Department along with Catholic social and academic institutions.

"We invite everyone to consider what we can each bring to the table," said Maryann Cusimano Love, professor of international relations at the Catholic University of America.

"Our meeting is not a retrospective 'Pacem in Terris' in the rearview mirror," she said, "but instead it is an inquiry into how we are living out the goals of 'Pacem in Terris,' of building sustainable peace by protecting human rights against the backdrop of challenges of 21st century conflicts."

Catholics from around the United States were in attendance, and Cardinal Peter Turkson of Ghana – who will speak at a plenary on Wednesday – made an appearance during the final sessions of the day.

Wednesday's topics will include the role of youth sports in peace building, diplomacy and reconciliation, peace praxis in Africa and discussion on the future of Catholic peacekeeping.