From the Catechism of the Catholic Church Imprimi Potest. Joseph Cardinal Ratzinger (Pope Benedict)
vatican.va/archive/ccc_css/archive/catechism/p123a9p3.htm#I
816 "The sole Church of Christ [is that] which our Savior, after his Resurrection, entrusted to Peter’s pastoral care, commissioning him and the other apostles to extend and rule it. . . . This Church, constituted and organized as a society in the present world, subsists in (subsistit in) the Catholic Church, which is governed by the successor of Peter and by the bishops in communion with him."267
The Second Vatican Council’s Decree on Ecumenism explains: "For it is through Christ’s Catholic Church alone, which is the universal help toward salvation, that the fullness of the means of salvation can be obtained. It was to the apostolic college alone, of which Peter is the head, that we believe that our Lord entrusted all the blessings of the New Covenant, in order to establish on earth the one Body of Christ into which all those should be fully incorporated who belong in any way to the People of God."268
818 "However, one cannot charge with the sin of the separation those who at present are born into these communities [that resulted from such separation] and in them are brought up in the faith of Christ, and the Catholic Church accepts them with respect and affection as brothers . . . . All who have been justified by faith in Baptism are incorporated into Christ; they therefore have a right to be called Christians, and with good reason are accepted as brothers in the Lord by the children of the Catholic Church."272
819 "Furthermore, many elements of sanctification and of truth"273 are found outside the visible confines of the Catholic Church: "the written Word of God; the life of grace; faith, hope, and charity, with the other interior gifts of the Holy Spirit, as well as visible elements."274 Christ’s Spirit uses these Churches and ecclesial communities as means of salvation, whose power derives from the fullness of grace and truth that Christ has entrusted to the Catholic Church. All these blessings come from Christ and lead to him, 275 and are in themselves calls to "Catholic unity."276
Excerpt of Dogmatic Constitution of the Catholic, LUMEN GENTIUM, solemnly promulgated by his holiness Pope Paul v1 on November 21, 1964
vatican.va/archive/hist_councils/ii_vatican_council/documents/vat-ii_const_19641121_lumen-gentium_en.html
"15. The Church recognizes that in many ways she is linked with those who, being baptized, are honored with the name of Christian, though they do not profess the faith in its entirety or do not preserve unity of communion with the successor of Peter. (14*) For there are many who honor Sacred Scripture, taking it as a norm of belief and a pattern of life, and who show a sincere zeal. They lovingly believe in God the Father Almighty and in Christ, the Son of God and Saviour. (15*) They are consecrated by baptism, in which they are united with Christ. They also recognize and accept other sacraments within their own Churches or ecclesiastical communities. Many of them rejoice in the episcopate, celebrate the Holy Eucharist and cultivate devotion toward the Virgin Mother of God.(16*) They also share with us in prayer and other spiritual benefits.
Likewise we can say that in some real way they are joined with us in the Holy Spirit, for to them too He gives His gifts and graces whereby He is operative among them with His sanctifying power. Some indeed He has strengthened to the extent of the shedding of their blood. In all of Christ’s disciples the Spirit arouses the desire to be peacefully united, in the manner determined by Christ, as one flock under one shepherd, and He prompts them to pursue this end. (17*) Mother Church never ceases to pray, hope and work that this may come about. She exhorts her children to purification and renewal so that the sign of Christ may shine more brightly over the face of the earth."