Your question is a very good one, but is complex and has several different aspects that need to be addressed.
The ordinary method of salvation is through the Catholic Church. That is the intention of Christ when he commanded his Apostles to baptize the nations and teach them to observe His commandments. However, this does not exclude those who, through no fault of their own, have never been exposed to authentic Catholic teaching and don’t recognize the Catholic Church to be the one which Christ founded. This is called “invincible ignorance.” Many of the more liberal-minded Catholics today tend to use this as a legal loophole to advocate the heresy of universal salvation, but invincible ignorance is very specific: it is an ignorance which exists
through no fault of their own. Since it is a relatively easy matter in our time to research Catholicism and to contact one’s local parish priest for more information, there are very few cases in which ignorance can truly be invincible. Thus, the ordinary means of salvation, except in rare and extraordinary cases, is participation within the One, Holy. Catholic, and Apostolic Church.
It has been taught authoritatively that those who reject Christ and strive against his Church are excluded from salvation; for instance, Pope Pius IX said in his Quanto conficiamur moerore:
“But it is also a Catholic dogma, that no one outside the Catholic Church can be saved, and that those who are contumacious against the authority of the same Church [and] definitions and who are obstinately separated from the unity of this Church and from the Roman Pontiff, successor of Peter, to whom the custody of the vineyard was entrusted by the Savior, cannot obtain eternal salvation.”
Even those members in “invisible union” with the Catholic Church are at risk, since they do not have the infallible guidance of the Magisterium, nor the Sacraments to keep them living members:
“They who do not belong to the visible bond of the Catholic Church… [we ask them to] strive to take themselves from that state in which
they cannot be sure of their own eternal salvation; for even though they are ordered to the mystical body of the Redeemer by a certain desire and wish of which they are not aware [implicit in the general wish to do what God wills], yet they lack so many and so great heavenly gifts and helps which can be enjoyed only in the Catholic Church.” (Pope Pius XII, Mystici Corporis)
And, as the letter from the Holy Office regarding Fr. Feeney’s heresies states, one must not only have explicit/implicit desire, but true charity to effect such an invisible union:
“But it must not be thought that any kind of desire of entering the Church suffices that one may be saved. It is necessary that the desire by which one is related to the Church be animated by perfect charity.”
Charity being a supernatural virtue, it would be nearly impossible to maintain perfect Charity without aid of the Sacraments and the many helps provided only through the Catholic Church.
Finally, we have the idea prevalent among the so-called Progressives that there is a “dual covenant,” wherein the Jews’ old covenant is still in effect alongside the eternal covenant of Christ. This is most probably a heresy, and is certainly bad theology. The old covenant of the Jews was a foreshadowing and prefiguring of the new and everlasting covenant of Christ. When the true covenant came into effect, the old was superseded because there was no longer any need for shadows and allegories. It is unthinkable and indeed absurd to hold the dogma of the Church, “Outside the Church, there is no salvation,” all the while holding that there is a separate covenant outside the Church which leads to salvation! Pope John Paul II explicitly stated in his Redemptoris Mater:
“Christ fulfills the divine promise and supersedes the old law.”
Our Pope, while Cardinal, also wrote:
“Thus the Sinai [Mosaic] Covenant is indeed superseded” (Many Religions – One Covenant, p. 70).
A fuller treatment of the topic can be found here:
catholicintl.com/articles/The%20Old%20Covenant%20Revoked%20or%20Not%20Revoked%20for%20Culture%20Wars.pdf
So, with these topics in mind, we can safely say that salvation is open to non-Catholics who fulfill the criteria of invincible ignorance, explicit desire (implicit in the case of invincible ignorance), and perfect Charity which links them in an invisible way with the Visible Body of Christ; but this is true only in extraordinary circumstances, and in our day and age, it would be very difficult if not virtually impossible for these conditions to be fulfilled due to the accessibility of the Catholic Church, and the difficulty of maintaining grace in our increasingly sinful culture. Even if these conditions were met, salvation would still be an uncertain matter. It’s best not to presume God’s mercy over his justice, and push for the ordinary participation within the Church to ensure the means of salvation are available.
In the case of Jews practicing Judaism, it would be virtually impossible unless they were to reject their religion. This is because their religion explicitly rejects Christ, the Church, and its Dogmas as an inherent principle of faith, views which close the door to salvation. Besides, it is not the religion which Christ founded, and is thus inherently deficient to begin with; salvation could only be obtained despite such a religion, not because of it. There is only one covenant which leads to salvation, and that is through Christ and the Church which he founded on Peter. Any alternative can’t be maintained without violating the dogma of the Church, “Extra Ecclesiam, Nulla Salus.”
Just my (fallible) opinions!
