That has been discussed, but here, too, there has been a development of all that was said in the Church, beginning with St. Cyprian, one of the Fathers of the Church, in the third century. Again, the perspective is different between then and now. In the third century, some Christian groups wanted to be outside the Church, and what St. Cyprian said is that without the Church a Christian cannot be saved. The Second Vatican Council also said this: Lumen Gentium 14 says: “Whosoever, therefore, knowing that the Catholic Church was made necessary by Christ, would refuse to enter or to remain in it, could not be saved.” He who is aware of the presence of Revelation is obliged by his conscience to belong publicly — and not only in his conscience, in his heart — to this Catholic Church by remaining in communion with the Pope and those bishops in communion with him.
But we cannot say that those who are inculpably ignorant of this truth are necessarily condemned for that reason. We must hope that those who do not belong to the Church through no fault of their own, but who follow the dictates of their God-given conscience, will be saved by Jesus Christ whom they do not yet know. Every person has the right to act according to his or her own conscience.- Cardinal Gerhard Muller (10/02/2012 ). Archbishop Gerhard Müller: 'The Church Is Not a Fortress', National Catholic Register http://www.ncregister.com/daily-news/archbishop-mueller-the-church-is-not-a-fortress/#ixzz3pwkg3Mur