"One indeed is the universal Church of the faithful, outside which no one at all is saved, in which the priest himself is the sacrifice, Jesus Christ, whose body and blood are truly contained in the sacrament of the altar under the species of bread and wine; the bread (changed) into His body by the divine power of transubstantiation, and the wine into the blood, so that to accomplish the mystery of unity we ourselves receive from His (nature) what He Himself received from ours."
--Pope Innocent III and Lateran Council IV (A.D. 1215)
"We are compelled in virtue of our faith to believe and maintain that there is only one holy Catholic Church, and that one is apostolic. This we firmly believe and profess without qualification. Outside this Church there is no salvation and no remission of sins, the Spouse in the Canticle proclaiming: 'One is my dove, my perfect one. One is she of her mother, the chosen of her that bore her' (Canticle of Canticles 6:8); which represents the one mystical body whose head is Christ, of Christ indeed, as God. And in this, 'one Lord, one faith, one baptism' (Ephesians 4:5). Certainly Noah had one ark at the time of the flood, prefiguring one Church which perfect to one cubit having one ruler and guide, namely Noah, outside of which we read all living things were destroyed… 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, Bull Unam sanctam (A.D. 1302)
The 1992 Catechism of the Catholic Church explained this as "all salvation comes from Christ the Head through the Church which is His Body."[3]
This expression comes from the writings of Saint Cyprian of Carthage, a bishop of the third century. The axiom is often used as shorthand for the doctrine that the Church is necessary for salvation. It is a dogma in the Catholic Church and the Eastern Orthodox churches in reference to their own communions. It is also held by many historic Protestant churches. However, Protestants, Catholics and the Orthodox each have a unique ecclesiological understanding of what constitutes the Church. For some the church is defined as "all those who will be saved", with no emphasis on the visible church.[1] For others the theological basis for this doctrine is founded on the beliefs that (1) Jesus Christ personally established the one Church; and (2) the Church serves as the means by which the graces won by Christ are communicated to believers.