This part was the most surprising of all the article. I cannot imagine what the author means by saying doctrines such as the trinity, the Deity of Jesus Christ, his propitiatory death for sin, the grace of God, salvation by grace through faith and all the essential doctrines that go into making Christianity do "not have the same importance as teachings deemed infallible". Seeing that the author identifies only the Assumption of Mary as falling under the heading of "Infallible teachings", I find it astonishing that these other core doctrines are not seen as important as a doctrine that is nowhere even found in Scripture and has no relation at all to what needs to be believed in order to be saved.
He explains that the reason is "Infallibly" defined doctrines "have a greater binding force precisely because they are closely connected with the essentials of revelation". To me, he is saying that extra-Bibical, "special" revelation of these doctrines makes them MORE important that Biblically revealed truths. Am I understanding this correctly and do you agree with him?
No, the Catholic Church says that these doctrines are equally infallible with scripture. (The Council of Trent itself infallibly defined the Biblical Canon so the Bible is itself part of those "special" doctrines defined as infallible).
The Church believes all Public Revelation (The Deposit of Faith) is divided into two parts. The Scriptures and Sacred Tradition. Scriptures are the part of Revelation that the apostles and prophets wrote down, the unwritten parts of Revelation that were taught by Christ to the Apostles and handed down orally are called Sacred Tradition. When the pope/Ecumenical Council promulgate an infallible definition, they cannot create/receive new revelations, they can only clarify whether a teaching has always been in or is compatible with the Deposit of Faith or not. Here is what the Council of Trent had to say concerning the scriptures:
The sacred and holy, ecumenical, and general Synod of Trent,—lawfully assembled in the Holy Ghost, the same three legates of the Apostolic See presiding therein,—keeping this always in view, that, errors being removed, the purity itself of the Gospel be preserved in the Church; which (Gospel), before promised through the prophets in the holy Scriptures, our Lord Jesus Christ, the Son of God, first promulgated with His own mouth, and then commanded to be preached by His Apostles to every creature, as the fountain of all, both saving truth, and moral discipline; and seeing clearly that this truth and discipline are contained in the written books, and the unwritten traditions which, received by the Apostles from the mouth of Christ himself, or from the Apostles themselves, the Holy Ghost dictating, have come down even unto us, transmitted as it were from hand to hand; (the Synod) following the examples of the orthodox Fathers, receives and venerates with an equal affection of piety, and reverence, all the books both of the Old and of the New Testament—seeing that one God is the author of both —as also the said traditions, as well those appertaining to faith as to morals, as having been dictated, either by Christ's own word of mouth, or by the Holy Ghost, and preserved in the Catholic Church by a continuous succession.
All of those essential doctrines that you mentioned above are already infallibly defined doctrines, so yes they do have the same importance as teachings deemed to be infallible. (All essential doctrines that Christ taught for salvation are of their very nature infallible whether or not the Church has explicitly defined them as such thus far. However, not all dogmas are explicitly defined, some are infallible and have always been taught by the Church as the truth, but they have not yet been defined because they have not been directly denied by members of the Church. These doctrines are infallible teachings of the Ordinary and Universal Magisterium ( the Magisterium is the teaching authority of the Church).
However, if an infallible doctrine of the Ordinary and Universal Magisterium comes under attack or is questioned by the faithful, it sometimes becomes necessary for the Church to explicitly state that a certain truth is infallible to help prevent the faithful from being led into error. When the Church does this, a doctrine moves from being infallible under the Ordinary and Universal Magisterium to being infallible under the Extraordinary Magisterium. Both the extraordinary and Universal Magisterium are equally binding, it's just more obvious and explicit when things are declared infallible under the Extraordinary Magisterium.
Rome rarely has infallibly defined a Scripture text, and within the (often general) parameters Rome provides RCs have much liberty to use texts to support her teachings ( often engaging in much extrapolation), though her teachings do not depend upon the exegetical weight of Scriptural evidence, not are the arguments or reasoning's behind an infallible decree necessarily infallible themselves.
As for disagreeing, besides which teachings belong are infallible (thus requiring "assent of theological faith") being open to interpretation, most of what RCs believe and practice is said to come from the Ordinary magisterium (requiring "religious submission of will and intellect"), and Catholics argue whether one may withhold assent from some of its teachings. Donum Veritatis does allow for conscientiously withholding of assent to a non-irreformable magisterial teaching (presuming he knows it is), though he is he is to refrain from speaking publicly, and be teachable and willing to submit to correction.
Conscience also is given a high priority in determining what a soul can assent to, though conscience does not constitute an autonomous and exclusive authority for deciding the truth of a doctrine.
"Over the pope as the expression of the binding claim of ecclesiastical authority there still stands one's own conscience, which must be obeyed before all else, if necessary even against the requirement of ecclesiastical authority. Conscience confronts [the individual] with a supreme and ultimate tribunal, and one which in the last resort is beyond the claim of external social groups, even of the official church" (Pope Benedict XVI [then Archbishop Joseph Ratzinger], Commentary on the Documents of Vatican II, ed. Vorgrimler, 1968, on Gaudium et spes, part 1,chapter 1.).
Understanding, and explaining inconsistencies becomes more difficult when examining all of what popes and Rome have taught, including canon law, which once forbade laymen from engaging in the kind of debate seen here.
"...Hence it is that the study of Canon Law is beset with almost inextricable difficulties, the door is open to disputes and litigations, consciences are troubled with a thousand anxieties, and people are driven to despise the law." (General Legislation in the New Code of Canon Law, pp. 70,71)