I found this discussed on another Catholic forum
"In relation to the issue of the 841-848 Section of the Catechism regarding non-Catholics being somehow involved in the plan of salvation I say that that statement is completely FALSE
One point we must all firstly understand and agree on is that the Catechism is not Dogmatic, it is Doctrine. What is in the Catechism is only based on Dogma.
I am a traditional Tridentine Catholic, and believe that the produce of Vatican II ‘watered down’ aspects of the Mass and Doctrine due to ambiguous text which was the work of Protestant and Freemason Bishops (which is a whole other story) in the hope to form ‘unity’ between Christians, weaken our faith, to modernize and to promote a sense of inclusiveness to peoples of other faiths.
This ‘watering down’ is evident in the 841-848 sections of the 1983 Catechism proceeding Vatican II.
To believe that Muslims, Jews schismatics, heretics or the pagans can enter the Kingdom of God is directly contradicting and challenging Ex Cathedra and Church Dogma which has been reinforced time and time again by numerous Popes. If you do not agree with Church Dogma or oppose Ex Cathedra then you are a Heretic. He is Papally Infalliable and if you do not believe that then you might aswell leave the church and go join some Eastern Orthodox rite.
“The most Holy Roman Catholic Church firmly believes, professes, and preaches that none of those existing outside the Catholic Church, not only pagans, but also Jews, 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 [the Catholic Church]. Pope Eugene IV, Council of Florence, Bull Cantate Domino, 1441
Pope Eugene IV spoke as Ex Cathedra which we all know falls under Papal Infallibility meaning that what he said was inspired directly by the Holy Spirit therefore being absolutely correct.
Other examples include;
“With our hearts we believe and with our lips we confess but one Church, not that of the heretics, but the Holy Roman Catholic and Apostolic Church, outside which we believe that no one is saved.” Pope Innocent III, Fourth Lateran Council, 1215.
“With Faith urging us we are forced to believe and to hold the one, holy, Catholic Church and that, apostolic, and we firmly believe and simply confess this (Church) outside which there is no salvation nor remission of sins” Pope Boniface VIII, Bull Unam Sanctum, 1302.
This point is further supported by ALL the Early Church Fathers including Ignatius of Antioch, Clement of Alexandria and Cyprien of Carthage. Apart from Church Fathers it is also adamantly reinforced by the great Church Doctors and Saints including St. Thomas Aquinas, St. Jerome, St. Augustine St. Peter Julian Eymard, St. John Vianney and St. Prosper of Aquitaine.