The notion that Rome doesn’t modify authoritative teaching such as the articles and canons of Trent is, with all due respect, out of step with reality. If you were looking for an example of a church that hasn’t changed for over a millennium, you’ll want to consider Eastern Orthodox Churches, not Rome. In the words of Calvin Scholar A.N.S. Lane,
The Roman Catholic Church, by contrast, has in the last generation changed more than the great majority of Protestant churches. This reality is often obscured by the Roman method of changing, which is not to disown the past but to reinterpret it. If we expect the Roman Church to disown Trent we will have a long wait; if we want to see Trent reinterpreted, we need only look around.
Before looking specifically at Trent, let us consider what might be the most vivid illustration of how Rome modifies her doctrine. Ever since Pope Boniface VIII promulgated Unam Sanctam in 1302, the Catholic Church has unequivocally asserted that there is “no salvation outside of the [Catholic] Church” (extra Ecclesiam nulla salus). Boniface pressed the idea more vigorously than his predecessors by declaring that it is absolutely necessary for salvation that every human creature be subject to the Roman Pontiff. The less audacious version actually reaches back to Cyprian in the third century. It is among the most basic affirmations of the Catholic tradition and therefore it is employed with full authority; however, the meaning is now radically different from what it has been in previous centuries. You might say it’s a 180 degree difference. Read through the lens of Vatican II, it now means that sincere Buddhists and even atheists can be saved (Lumen Gentium 2:16; Gaudium et spes 22). The belief that God desires salvation to reach all people, coupled with the conviction that such redemption may occur through Jesus Christ apart from one’s conscious awareness, led Rome to develop her teaching on this point in a much different direction from what it originally seemed to say.
A tangible, if not dramatic, example of this sort of revision unfolded in Boston in 1949 (before Vatican II) when a zealous Catholic priest, Father Feeney of Boston, insisted on the traditional interpretation of extra Ecclesiam nulla salus (that only Catholics can be saved). After an extended period of warnings, Feeney was excommunicated by Rome as an obstinate rigorist. Thus, the church excommunicated a priest for holding a traditional interpretation, while it simultaneously asserted that the doctrine remains the same (semper eadem). This is how the Roman Catholic Church implements doctrinal revision: it retains the formulation while interpreting its meaning in a different light.
After the Council of Trent (1545-63), previous councils were naturally understood through the lens of Trent. The Tridentine grid became normative for Catholic teaching and remained such for four hundred years. Vatican I (1869-70) continued in the same vein. Then came Vatican II (1963-65) and a new interpretive filter was introduced. Where Trent stated that Protestants (who maintain sola fide and resist the authority of Rome) are lost, Vatican II introduced hermeneutical categories that call this conclusion into question.
How do these interpretive categories work? Catholic theologian Hans Küng provides an example when he claims of Trent that “the Church. . . never looked at these decisions as rigid and frozen formulations, but rather as living signposts for continued research. . . .” This is the sort of theologizing for which Catholic scholars are famous. “Living signposts,” what does that mean? I haven’t a clue. The point for us to grasp is that statements of Catholic doctrine are not simply defined according to the intent of the original author (as we evangelicals are accustomed to doing exegesis); they are rather understood and applied according to contemporary perspectives.
Castaldo goes on to look at the suggestion that the Catechism of the Catholic Church unambiguously reaffirms the Tredentine teaching, and answers “Yes and no.”
Castaldo thinks that “the Catholic method of re-appropriating its doctrine through a developmental hermeneutic is problematic on an ethical level.” The result is that “the Catholic Church has painted herself into a corner by investing magisterial conclusions with an immutable character such that she isn’t able to say, ‘We were wrong.'” But it also behooves us as evangelicals to point out this problem and to deal with where they are at today.
You can read the whole thing here.