You bring up an excellent point that gets at the heart of the difference between Catholics and Protestants. Some of the Catholic doctrines cannot be accepted until one accepts the concept of apostolic succession. If there is a Magisterium given divine sanction to interpret scripture, then whatever they teach is Truth, regardless of how great or tenuous its scriptural support.
In a later reply, you say that the difference between an argument an a proof is the "open-and -shut" character of a proof. Proof leaves no possibility of the opposite conclusion's being true, I take it. But how does this change what I was saying earlier, that in order to follow a proof, one needs to be a practitioner of a tradition of exegesis that cultivates the capacity to see the "open-and-shut" character of a proof? You say that you are no longer an apprentice, because now you are a pastor. But neither the Pope nor any good Bishop of the Catholic Church would say such a thing. You never graduate from a state of apprenticeship in understanding Scripture. Even the Pope is still an apprentice in reading Scripture aright, an apprentice of the saints, popes, councils, etc. who have gone before. Even the Bishops of the Catholic Church consider themselves beholden to other Christians who have gone before. You do not so consider yourself. You have "graduated" and are now no longer an apprentice in a tradition, you need no further instruction. I guess you know it all. I am not saying this to be rude or nasty, but it is an implication of your self-understanding. This leads to the second point. You say:
We consider them decisively authoritative OVER the church. You consider the Church decisively authoritative OVER the scripture.
It is just simply false to say that Catholics think of the Church as authoritative over Scripture. The Church is not authoritative over the Scripture (I'll take up the canonicity question below). It is authoritative over ME and MY UNDERSTANDING of Scripture. There is a tremendous difference. Without recognizing such a distinction between Scripture in itself and me and my understanding of Scripture, I would need to hold the following: Scripture means exactly what I think it means and nothing more and nothing less. Now, I do not know about you, but I find Scripture in itself to be rich, complex, baffling and an opening to an infinite mystery to us. I am not so self-overestimating of my current cognitive condition that I think the following to be true: If Scripture seems to me to say that A, then necessarily, Scripture says that A, and if it does not seem to me that Scripture says that A, then Scripture does not say that A. Rather, I honestly admit that there is, and always will be so long as I am in this body, more to understand of what Scripture is saying than I realize at any one point. I also admit that what I shall discover in the future can drastically alter how I think of the Scripture I currently think I understand. Finally, I do not think of myself as having some guarantee of tracking the Scriptural truth with perfect accuracy. If all believers had such a guarantee, why do some believers sometimes make mistakes in understanding Scripture. So the Church is authoritative over me and my understanding of Scripture, and not over Scripture itself. Rather, the Church uses Scripture to correct my and my understanding of Scripture,and the Church is in a position to do so because it has, prior to me, a right understanding of Scripture. That right understanding is embodied in the sacred tradition, which we believe also proceeds from the VERBUM DEI -- Jesus Christ. The Church uses Scripture to correct me, and correct my fellow believers. But the Church does not, and cannot, correct Scripture. That would be stupid.
Some Catholics may want to argue that the Church is authoritative over Scripture because the Church drew up the canon. But the Church's drawing up of the canon is the cause of my knowledge of the canon, it is not the cause of the texts of the canon being inspired. The Church selected those texts because they are inspired, it is not that they are inspired because the Church says so. However, when it comes to my knowledge of which texts are canonical, I know that theese texts are inspired because the Church says so. God is the cause of the inspiration, the Church is the cause of my knowledge that these are the inspired texts. That the Church is the cause of my knowledge does not imply that the Church has authority over the Scriptures, but only that it has authority over me and my understanding. I heed to this authority over me and my understanding for a cumulation of reasons. Here are two. First,I believe it to be the revealed truth that I should do so, and that in doing so, I shall come to know all the things I do not yet know, but want to know, especially about how to read Scripture aright, what Scripture really means in its infinite depths. Second, without heeding to this authority, I will end up, like Protestants, with a whole bundle of false dichotomies: either Scripture or tradition, either follow Christ or follow the Church, either faith or works, either justification or sanctification, either the Church is auhtoritative over Scripture or the Scriptures are authoritative over the Church. What I do, instead, is simulataneously affirm that these three -- Scripure, Sacred Tradition, and Magisterium -- are inseparble, mutually requiring each other for the sake of the perfect transmission of the whole VERBUM DEI to the human race, and therefore to me. Tear these three apart and the result is a never ending conflict about the very foundations of Christianity. This is what Protestants look like. There is disagreement in the Catholic Church about different doctrines, but it is disagreement constrained by and argued out in terms of shared standards (except in recent years when the Protestant mentality has taken root in teh Church and so damaged its unity). In Protestantism , there are shared beliefs, but the foundations themselves are permanently in question -- shot through with dilemma after dilemma where there need be no dilemma at all.