Salvation is found only within the Catholic Church and though that has been the central truth of our Church since founded by Christ, it is a message always needing reaffirmation.
The central point of this magnificent document from the Congregation for the Doctrine of the Faith, is in three statements:
1) “Therefore, in connection with the unicity and universality of the salvific mediation of Jesus Christ, the unicity of the Church founded by him must be firmly believed as a truth of Catholic faith. Just as there is one Christ, so there exists a single body of Christ, a single Bride of Christ: “a single Catholic and apostolic Church”. Furthermore, the promises of the Lord that he would not abandon his Church (cf. Mt 16:18; 28:20) and that he would guide her by his Spirit (cf. Jn 16:13) mean, according to Catholic faith, that the unicity and the unity of the Church — like everything that belongs to the Church's integrity — will never be lacking.” (#16)
2) “Therefore, there exists a single Church of Christ, which subsists in the Catholic Church, governed by the Successor of Peter and by the Bishops in communion with him. The Churches which, while not existing in perfect communion with the Catholic Church, remain united to her by means of the closest bonds, that is, by apostolic succession and a valid Eucharist, are true particular Churches. Therefore, the Church of Christ is present and operative also in these Churches, even though they lack full communion with the Catholic Church, since they do not accept the Catholic doctrine of the Primacy, which, according to the will of God, the Bishop of Rome objectively has and exercises over the entire Church.” (#17)
3) “Above all else, it must be firmly believed that “the Church, a pilgrim now on earth, is necessary for salvation: the one Christ is the mediator and the way of salvation; he is present to us in his body which is the Church. He himself explicitly asserted the necessity of faith and baptism (cf. Mk 16:16; Jn 3:5), and thereby affirmed at the same time the necessity of the Church which men enter through baptism as through a door”. This doctrine must not be set against the universal salvific will of God (cf. 1 Tim 2:4); “it is necessary to keep these two truths together, namely, the real possibility of salvation in Christ for all mankind and the necessity of the Church for this salvation”. (#20)
There is an excellent article about Dominus Iesus, by Peter Kreeft, in the National Catholic Register.
“Dominus Iesus, published Aug. 6, 2000, by the Congregation for the Doctrine of the Faith, is one of the most important Church documents of modern times because it concerns what is absolutely central and primary in Christianity, Christ himself, because it defends the most unpopular aspect of the Church’s claim today — its “absolutism” — and because it overcomes the dualism of “liberal” vs. “conservative” by which the media classify and evaluate everything….
“When Dominus Iesus was issued, both groups gagged. The Fundamentalists found it too liberal and universalistic, and the Liberals found it too conservative and exclusivist. It’s not surprising that it happened to Dominus Iesus because the same thing happened to Jesus himself: Sadducees and Pharisees, Herodians and Zealots, suddenly found one thing to agree about. They had found their common enemy.
“Throughout Christian history the pattern has repeated itself. There have always been the “faith alone” fundamentalists (Tatian, Tertullian, Bernard, Luther) and the “reason trumps faith” liberals (Origen, Abelard, Spinoza, Bultmann), but also the “both-and” defenders of mainline orthodoxy (Justin Martyr, Augustine, Aquinas, Newman, Chesterton). …
“Dominus Iesus not only overcomes the “liberal”/“conservative” divide but it also unites the positive in both while rejecting the negative. It is not a compromise but a “higher synthesis.” …
“The three main points of this document concern (1) Christ, (2) the Catholic Church, and (3) the Kingdom of God. The first is the longest and most important. Its central passage says that:
“God, who desires to call all people to himself in Christ … does not fail to make himself present in many ways, not only to individuals, but also to entire peoples through their spiritual riches, of which their religions are the main and essential expression even when they contain ‘gaps, insufficiencies and errors.’ Therefore the sacred books of other religions, which in actual fact direct and nourish the existence of their followers, receive from the mystery of Christ the elements of goodness and grace which they contain.
“The salvific action of Jesus Christ, with and through his Spirit, extends beyond the visible boundaries of the Church to all humanity … for all men of good will in whose hearts grace is active invisibly. For since Christ died for all, and since all men are in fact called to one and the same destiny, which is divine, we must hold that the Holy Spirit offers to all the possibility of being made partners, in a way known to God, in the paschal mystery.” But “they acquire meaning and value only from Christ’s own mediation, and they cannot be understood as parallel or complementary to his.”