John Paul II presents the pursuit of Christian unity, urged by the Second Vatican Council and the approach of the Jubilee of 2000, as essential to the Church’s witness to Christ. Because division contradicts Christ’s prayer and the unity given in Baptism, ecumenism seeks to develop imperfect communion into full, visible communion, acknowledging the truth and holiness present in other Christian communities while affirming the fullness of Christ’s Church in Catholic communion. The path requires conversion, repentance, prayer, holiness, purification of historical memories, and dialogue understood as an exchange of gifts governed by truth rather than false irenicism. The Pope gives particular attention to the Eastern Churches: the lifting of the 1054 excommunications, the first millennium’s model of “Sister Churches,” the “two lungs” of East and West, and continuing theological dialogue point toward restored communion. Sacramental sharing with Orthodox Christians may be permitted in particular circumstances because of their close sacramental bond with the Catholic Church. Relations with communities born of the Reformation build on shared baptism, Scripture, prayer, holiness, and service while confronting differences over authority, ministry, Orders, sacraments, and the Eucharist. The document identifies the Bishop of Rome’s Petrine ministry as a humble service of love and invites discussion of a form of primacy acceptable to other Christians. Unity is indispensable to credible evangelization, and all the baptized are called to pursue it through prayer, reconciliation, gratitude, and hope.