At dinner tonight after Mass, I just learned that a lot of people at my SSPX chapel are borderline or full blown Feeneyites. Baptism is necessary baby! Father Feeney was a saint!
In the U.S. of A. they say
Feeneyism (Feeney was simple Priest and Jesuit). Elsewhere it's just called Catholicism to believe that the sacrament of baptism is necessary for salvation.
The Council of Trent explains that one can't even have faith, have hope, or have charity, if not justified by the sacrament of baptism. After quite some preparation, by the sacrament, man
receives, in the said justification, together with the remission of sins, all these (gifts) infused at once, faith, hope, and charity.
The faith is not an opinion of man. The faith must be infused by the sacrament, infused into a man desiring the faith.
A Catechumen may, in a human way, already be convinced that the one true religion is the one true religion, but that's not the true faith. Before they're baptized, they can do no more than beg for the true faith:
This faith, Catechumen’s beg of the Church-agreeably to a tradition of the apostles-previously to the sacrament of Baptism;
No justification without causes:
the instrumental cause is the sacrament of baptism, which is the sacrament of faith
No faith without sacrament.
Some folks talk about "supernatural faith". Well, that's what is infused from above at the reception of the sacrament, as quoted above. All else would be "self redemption" by being "nice".