The Roman Catholic Archbishop of Dublin, Dr Diarmuid Martin, has urged the main Christian churches to cooperate in facing the challenges posed by secularisation.
Meanwhile, his Church of Ireland counterpart Dr Michael Jackson said Christians need to garner the good news that has come out of the Peace Process in the North.
They were speaking on the second day of the 50th International Eucharistic Congress in Dublin.
History was made during today’s proceedings, as the entire day of work and prayers will focus on the challenge of restoring Christian unity.
This is the first time in the Congress Movement's 131-year history that the search for Christian unity will preoccupy the pilgrims for an entire day.
This afternoon’s Liturgy of the Word and Water in the main RDS Arena celebrated the common baptism of all Christians and their shared debt to the Bible.
It was presided over by Dr Jackson, who was joined on the altar by the President of the Methodist Church in Ireland, the Rev Kenneth Lindsay, and Roman Catholic Bishop of Dallas Dr Brian Farrell.
It was only the second time ever, and the first time in a generation, that an ecumenical liturgy will have been celebrated at such a congress.
The initiative comes 50 years after the Second Vatican Council admitted that both sides were to blame for tearing the Church apart during the Reformation almost 500 years ago.
It is 40 years since Ireland removed the special position of the Catholic Church from the Constitution.