While dialogue among Christians is important, St. John Paul II believed that prayer played a vital role in achieving the ultimate goal of establishing Christian unity.
He explained his thoughts in his encyclical, Ut unum sint.
Love is given to God as the perfect source of communion—the unity of Father, Son and Holy Spirit—that we may draw from that source the strength to build communion between individuals and Communities, or to re-establish it between Christians still divided. Love is the great undercurrent which gives life and adds vigour to the movement towards unity.
This love finds its most complete expression in common prayer. When brothers and sisters who are not in perfect communion with one another come together to pray, the Second Vatican Council defines their prayer as the soul of the whole ecumenical movement. This prayer is “a very effective means of petitioning for the grace of unity,” “a genuine expression of the ties which even now bind Catholics to their separated brethren.”
This is one of the reasons why St. John Paul II would always pray with non-Catholic Christians wherever he went.
My visits have almost always included an ecumenical meeting and common prayer with our brothers and sisters who seek unity in Christ and in his Church. With profound emotion I remember praying together with the Primate of the Anglican Communion at Canterbury Cathedral (29 May 1982); in that magnificent edifice, I saw “an eloquent witness both to our long years of common inheritance and to the sad years of division that followed.” Nor can I forget the meetings held in the Scandinavian and Nordic Countries (1-10 June 1989), in North and South America and in Africa, and at the headquarters of the World Council of Churches.
If we ever want to establish true and lasting unity among Christians on earth, we need to pray together for that unity, asking God to heal the wounds of division.