10 In the present situation of the lack of unity among Christians and of the confident quest for full communion, the Catholic faithful are conscious of being deeply challenged by the Lord of the Church. The Second Vatican Council strengthened their commitment with a clear ecclesiological vision, open to all the ecclesial values present among other Christians. The Catholic faithful face the ecumenical question in a spirit of faith. The Council states that the Church of Christ "subsists in the Catholic Church, which is governed by the Successor of Peter and by the Bishops in communion with him", and at the same time acknowledges that "many elements of sanctification and of truth can be found outside her visible structure. These elements, however, as gifts properly belonging to the Church of Christ, possess an inner dynamism towards Catholic unity". "It follows that these separated Churches and Communities, though we believe that they suffer from defects, have by no means been deprived of significance and value in the mystery of salvation. For the Spirit of Christ has not refrained from using them as means of salvation which derive their efficacy from the very fullness of grace and truth entrusted to the Catholic Church".
Source: Ut Unum Sint (Vatican.va)