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.
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.
Identical. How can associations like the SSPX, Resistance, SSPV, and CMRI pretend to oppose Vatican II when they support the 1949 Holy Office Letter which teaches the same heresy?
These associations pretend to oppose the Novus Ordo, but they teach that heretics who go to Presbyterian, Anglican, or Lutheran services can be saved as long as they don't know that the Catholic Church is the true Church. Will those in the Novus Ordo be saved as long as they don't know that the Traditional Latin Mass is the true worship? If the blind followers of the blind will not fall into the pit after all, provided that they don't know any better, then what justification do these "traditional" associations have for existing?
The letter the Saint Benedict Center wrote to the SSPX many years ago is still very relevant:
You [the SSPX] very admirably defend the traditional Mass. But at the same time it seems evident to many that you uphold the heresy that was behind the implantation of the New Mass. What difference, may I ask, does it make what Mass one goes to, if his sincerity is what determines his state of soul? Some people are very sincere about Jehovah’s Witness services! Are they, according to your theology, to be blamed? If not, why do you insist Catholics stop going to the Novus Ordo? What right do you have to disturb their conscience, if salvation depends upon sincerity? You yourself admit that the dogma “No Salvation Outside the Church” really means that there is no salvation without the Church — as if the defining Church of the past had no idea what it really meant by choosing the Latin word “extra” rather than “sine.” You prefer to accent the general truth, which is more of a truism, and suppress the more specific truth, which is a challenge. Yet you find this same tactic abhorrent in the liturgical demolitionists who replaced the pro multis with “for all men.” http://catholicism.org/feeney-doctrine.html
Pope Saint Gregory the Great (A.D. 590 – 604): “Now the holy Church universal proclaims that God cannot be truly worshipped
saving within herself, asserting that all they that are without her shall never be saved.” (Moralia)
Pope Gregory XVI (A.D. 1831 – 1846): “It is not possible to worship
except in Her; all who are outside Her will not be saved.” (Encyclical, Summo Jugiter)
Pope Pius XI (A.D. 1922 – 1939): “The Catholic Church alone is keeping the true worship
. This is the font of truth, this is the house of faith, this is the temple of God; if any man enter not here, or if any man go forth from it, he is a stranger to the hope of life and salvation.” (Encyclical, Mortalium Animos)
As Fr. Wathen wrote, the dogma "outside the church there is no salvation" is the basis for the labors of all who seek to maintain and restore traditional Catholicity.