If he was validly baptized and never committed a mortal sin, he will be saved; because, believing himself a member of the true Church, he was doing all he could to serve God according to his knowledge and the dictates of his conscience. But if ever he committed a mortal sin, his salvation would be very much more difficult. A mortal sin once committed remains on the soul till it is forgiven. Now, how could his mortal sin be forgiven? Not in the Sacrament of Penance, for the Protestant does not go to confession; and if he does, his minister—not being a true priest—has no power to forgive sins. Does he know that without confession it requires an act of perfect contrition to blot out mortal sin, and can he easily make such an act? What we call contrition is often only imperfect contrition—that is, sorrow for our sins because we fear their punishment in Hell or dread the loss of Heaven. If a Catholic—with all the instruction he has received about how to make an act of perfect contrition and all the practice he has had in making such acts—might find it difficult to make an act of perfect contrition after having committed a mortal sin, how much difficulty will not a Protestant have in making an act of perfect contrition, who does not know about this requirement and who has not been taught to make continued acts of perfect contrition all his life. It is to be feared either he would not know of this necessary means of regaining God’s friendship, or he would be unable to elicit the necessary act of perfect contrition, and thus the mortal sin would remain upon his soul and he would die an enemy of God.
If, then, we found a Protestant who never committed a mortal sin after Baptism, and who never had the slightest doubt about the truth of his religion, that person would be saved; because, being baptized, he is a member of the Church, and being free from mortal sin he is a friend of God and could not in justice be condemned to Hell. Such a person would attend Mass and receive the Sacraments if he knew the Catholic Church to be the only true Church.
I am giving you an example, however, that is rarely found, except in the case of infants or very small children baptized in Protestant sects. All infants rightly baptized by anyone are really children of the Church, no matter what religion their parents may profess. Indeed, all persons who are baptized are children of the Church; but those among them who deny its teaching, reject its Sacraments, and refuse to submit to its lawful pastors, are rebellious children known as heretics.
I said I gave you an example that can scarcely be found, namely, of a person not a Catholic, who really never doubted the truth of his religion, and who, moreover, never committed during his whole life a mortal sin. There are so few such persons that we can practically say for all those who are not visibly members of the Catholic Church, believing its doctrines, receiving its Sacraments, and being governed by its visible head, our Holy Father, the Pope, salvation is an extremely difficult matter.