** Outside the church there is no salvation is a doctrine of the Catholic faith that was taught by Jesus Christ to his Apostles, preached by the fathers, defined by popes and councils, and piously believed by the faithful in every age of the church.
A doctrine, or dogma, of the church, is a truth which has been revealed by God and must be believed by all Catholics. When the pope teaches “Ex Cathedra” ( From the chair of Peter), he invokes his highest teaching authority, thus assuring the faithful that such a declaration is dogma.
Here is how three popes solemnly defined “Outside the Church there is no salvation”.
Ex Cathedra: There is but one Universal church of the faithful, outside which no one at all is saved. (Pope Innocent III, Fourth LAteran Council, 1215).
Ex Cathedra: We declare, say, define and pronounce that it is absolutely necessary for the salvation of every human creature to be subject to the Roman Pontiff. (Pope Boniface VIII, the Bull Unam Sanctam, 1302).
Ex Cathedra: The most Holy Roman Church firmly believes, professes and preaches that none of those existing outside the Catholic church, not only pagans, but also Jews and heretics and schismatics, can have a share in life eternal; but that they will go into the eternal fire which was prepared for the devil and his angels, unless before death they are joined with Her. No one, let his almsgiving be as great as it may, no one, even if he pour out his blood for the name of Christ, can be saved, unless he remain within the bosom and the unity of the Catholic church. (Pope Eugene IV, the Bull Cantate Domino, 1441)
All Catholics must believe this teaching. To reject it—or even to doubt it deliberately—is to sin mortally against the virtue of faith. Failure to hold and teach this doctrine has led to the present state of affairs in the church of God.