The Holy Office sent a letter to the archbishop of Boston regarding the Feeney case, in which the following is stated: “After having examined all the documents that are necessary or useful
in this matter . . . the same Sacred Congregation is convinced that the unfortunate controversy arose from the fact that the axiom, "outside the Church there is no salvation," was not correctly understood and weighed . . . However, this dogma must be understood in that sense in which the Church herself understands it. For, it was not to private judgments that Our Savior gave for explanation those things that are contained in the deposit of faith, but to the teaching authority of the Church . . . Not only did the Savior command that all nations should enter the Church, but He also decreed the Church to be a means of salvation without which no one can enter the kingdom of eternal glory. In His infinite mercy God has willed that the effects, necessary for one to be saved, of those helps to salvation which are directed toward man's final end, not by intrinsic necessity, but only by divine institution, can also be obtained in certain circumstances when those helps are used only in desire and longing . . . The same in its own degree must be asserted of the Church, in as far as she is the general help to salvation. Therefore, that one may obtain eternal salvation, it is not always required that he be incorporated into the Church actually as a member, but it is necessary that at least he be united to her by desire and longing. However, this desire need not always be explicit, as it is in catechumens; but when a person is involved in invincible ignorance God accepts also an implicit desire, so called because it is included in that good disposition of soul whereby a person wishes his will to be conformed to the will of God . . . These things are clearly taught in that dogmatic letter which was issued by the Sovereign Pontiff, Pope Pius XII, on June 29, 1943,
It is abundantly clear here that the Holy Office is intending to interpret the dogma “outside the Church there is no salvation,” in the manner in which the Church understands it. So, what is stated here? Here are the main points in order:
1) The Saviour decreed that the Church be a means of salvation without which no one can enter the kingdom of eternal glory.
2) At the same time, God has willed that the effects of the helps to salvation, which are necessary to be saved, can be obtained in certain circumstances when those helps are used only in desire or longing.
3) Statement number 2 applies to the Church, inasmuch as she is the general help to salvation.
4) Therefore, that one may obtain eternal salvation, it is not always required that a person be incorporated into the Church actually, but it is necessary to be united at least by desire and longing.
5) This desire need not be explicit; when a person has invincible ignorance, God accepts also an implicit desire, which is included in the disposition of soul by which someone wants his will to be conformed to God's will.
6) This desire must be animated by perfect charity, and the person must have supernatural faith.
Thus, the Holy Office states explicitly that it is not necessary to be actually united to the Church as a member to be saved, but one can be united through desire and longing, and this desire does not have to be explicit, but can be implicit.
Furthermore, its teaching on “no salvation outside the church” is very helpful for understanding where many have gone wrong on the teaching. It says that the Church is necessary for salvation by divine institution, and therefore it is up to God to decide whether a desire, even an implicit one, for the church should suffice for salvation. This explains what is meant when people talk about something, say baptism, being a necessity of means for salvation. Necessity of means is opposed to the necessity of precept. There is a necessity of precept when God or the Church commands something to be done in a particular way, which might be done in some other way. For example, it is necessary to give honor to God. But this can be done in various ways. It is a necessity of precept that we attend Mass on Sundays. There is a necessity of means when there is no other way for a man to accomplish something. Thus, for example, the Church is necessary by a necessity of means. But this simply means that there is no other means available to man. It doesn't mean that no other means is available to God.
The point being, that necessity of means is said with respect to men. To make this clearer, let's look at number 1257 from the CCC: "The Lord himself affirms that BAPTISM IS NECESSARY FOR SALVATION. He also commands his disciples to proclaim the Gospel to all nations and to baptize them. Baptism is necessary for salvation for those to whom the Gospel has been proclaimed and who have had the possibility of asking for this sacrament. THE CHURCH DOES NOT KNOW OF ANY MEANS OTHER THAN BAPTISM that assures entry into eternal beatitude; this is why she takes care not to neglect the mission she has received from the Lord to see that all who can be baptized are "reborn of water and the Spirit." GOD HAS BOUND salvation to the sacrament of Baptism, but HE HIMSELF IS NOT BOUND BY HIS SACRAMENTS."
Thus, even if someone were to say that explicit faith in Christ is necessary for salvation by a necessity of means, that can be true while at the same time there existing the possibility of someone being saved by an implicit faith, which is what is asserted here in the letter.
This fact allows us to refute the claim that some people make: that it is still necessary to have an explicit faith in Christ. These people say that the letter does not make any claims about the precise nature of this supernatural faith; i.e., does it have to be an explicit faith in Christ, or would an implicit faith suffice. It merely says that the desire for the Church can be implicit. Against this, several things should be noted. First, as was stated in the paragraph above, even if explicit faith in Christ is a necessity of means, this is by divine institution, and was stated in the letter, God is not bound to the things he institutes in such a way that he cannot allow an implicit faith to suffice where normally an explicit faith is required.
Second, the letter itself references Pius XII's encyclical Mystici Corporis, and says that this same teaching is taught in it. If we look at the passages of the encyclical that are referred to in the letter, we can see what kind of people fall under this possibility of salvation:
“Likewise, We must earnestly desire that this united prayer may embrace in the same ardent charity both those who, not yet enlightened by the truth of the Gospel, are still outside the fold of the Church, and those who, on account of regrettable schism, are separated from Us, who though unworthy, represent the person of Jesus Christ on earth . . . we have committed to the protection and guidance of heaven those who do not belong to the visible Body of the Catholic Church, solemnly declaring that after the example of the Good Shepherd We desire nothing more ardently than that they may have life and have it more abundantly. ”
It is very clear that Pius XII is excluding nobody here, but is referring to all those who are outside the visible Church, including those who have not been enlightened by the truth of the Gospel. While it is true that the phrase “not yet enlightened by the truth of the Gospel,” includes also those who know of the Gospel but have not accepted it, nevertheless it also includes those who do not know of the Gospel and have not accepted it. Hence, since he goes on to commit all those who do not belong to the visible Church to the protection of heaven, it is clear that he is referring to everyone who does not belong to the Church, regardless of whether or not he knows of Christ.
Note: The full text of the letter of the Holy Office to the Archbishop of Boston can be found here: http://www.columbia.edu/cu/augustine/arch/cdffeeney.txt