We are bound by divine and Catholic faith to believe all those things which are contained in the word of God, whether it be Scripture or Tradition, and are proposed by the Church to be believed as divinely revealed, not only through solemn judgment but also through the ordinary and universal teaching office.
Now, among those things which the Church has always preached and will never cease to preach is contained also that infallible statement by which we are taught that there is no salvation outside the Church.
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.
Now, in the first place, the Church teaches that in this matter there is question of a most strict command of Jesus Christ. For He explicitly enjoined on his apostles to teach all nations to observe all things whatsoever He Himself had commanded.
Now, among the commandments of Christ, that one holds not the least place, by which we are commanded to be incorporated by Baptism into the Mystical Body of Christ, which is the Church, and to remain united to Christ and to his Vicar, through whom He Himself in a visible manner governs the Church on earth.
Therefore, no one will be saved who, knowing the Church to have been divinely established by Christ, nevertheless refuses to submit to the Church or withholds obedience from the Roman pontiff, the Vicar of Christ on earth.
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. This we see clearly stated in the Sacred Council of Trent, both in reference to the Sacrament of Baptism and in reference to the Sacrament of Penance.
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, 1948, "On the Mystical Body of Jesus Christ". For in this letter the Sovereign Pontiff clearly distinguishes between those who are actually incorporated into the Church as members, and those who are united to the Church only by desire.
Discussing the members of which the Mystical Body is composed here on earth, the same August Pontiff says: "Actually only those are to be included as members of the Church who have been baptized and profess the true faith, and who have not been so unfortunate as to separate themselves from the unity of the Body, or been excluded by legitimate authority for grave faults committed".
Toward the end of this same Encyclical Letter, when most affectionately inviting to unity those who do not belong to the body of the Catholic Church, he mentions those who "are related to the Mystical Body of the Redeemer by a certain unconscious yearning and desire", and these he by no means excludes from eternal salvation, but on the other hand states that they are in a condition "in which they cannot be sure of their salvation" since "they still remain deprived of those many heavenly gifts and helps which can only be enjoyed in the Catholic Church".
With these wise words he reproves both those who exclude from eternal salvation all united to the Church only by implicit desire, and those who falsely assert that men can be saved equally well in every religion.
But it must not be thought that any kind of desire of entering the Church suffices that one may be saved. It is necessary that the desire by which one is related to the Church be animated by perfect charity. Nor can an implicit desire produce its effect, unless a person has supernatural faith: "For he who comes to God must believe that God exists and is a rewarder of those who seek Him". The Council of Trent declares: "Faith is the beginning of man's salvation, the foundation and root of all justification, without which it is impossible to please God and attain to the fellowship of his children".
Therefore, let them who in grave peril are ranged against the Church seriously bear in mind that after "Rome has spoken" they cannot be excused even by reasons of good faith. Certainly, their bond, and duty of obedience toward the Church is much graver than that of those who as yet are related to the Church `'only by an unconscious desire". Let them realize that they are children of the Church, lovingly nourished by her with the milk of doctrine and the sacraments, and hence, having heard the clear voice of their Mother, they cannot be excused from culpable ignorance, and therefore to them apply without any restriction that principle: submission to the Catholic Church and to the Sovereign Pontiff is required as necessary for salvation.