Private judgement (part 1)
(Here is a little bit of history) This doctrine was created and defined as a deliberate reaction against and rejection of historic Christian teaching. Ever since the earliest days of Church history, Christians had held that theology must be formulated according to three principles—Apostolic Scripture, Apostolic Tradition, and the Apostolic Magisterium (teaching authority) of the Church. The first two of these provided the data necessary to conduct theological investigation while the third served to authoritatively formulate the correct interpretation of the data presented by the two material sources. Thus Scripture and Tradition served as material principles of theology, while the Magisterium, by enabling us to know with certainty the correct interpretation of this material, served as a formal principle of theology.
Because the Protestant Reformers wished to hold teachings which were completely foreign to historic Christian theology, they had to reject the historic Christian method of formulating theology, and thus could not continue to accept the three principles of Scripture, Tradition, and Magisterium. They had to reject the teachings of the Magisterium because the Magisterium disagreed with them, and they likewise had to reject Tradition as a source, for it also disagreed with them. They were thus left in the position of trying to formulate theology in terms of a single principle—Scripture—and thus the doctrine of sola scriptura was born.
All of this is admitted, with varying qualifiers, by Protestant historians, as it is simply a historical fact that the doctrine of sola scriptura arose later in history than the original teachings of the Reformers. The Reformers proposed these teachings to the Church and, when the Magisterium refused to change it position and reaffirmed the historic Christian teachings on these matters, the Reformers were forced to eliminate both Magisterium and history (Tradition) from their theological method.
If the Magisterium, contrary to its mission and its indefectability, had changed its position and rejected the historic Christian teachings in favor of the new Protestant ones, then hypothetically it would not have needed rejection. A version of sola scriptura might have arisen in which only eliminated Apostolic Tradition. Sola scriptura would then have meant that one was to base one's theology on the material presented in Scripture alone but as interpreted by the living Christian Magisterium.
However, the Magisterium was prevented from endorsing the new Protestant doctrines by its indefectability in its mission of upholding the historic Christian teachings, and so such a version of sola scriptura never arose. The Magisterium, along with Apostolic Tradition, had to go and be excluded from the theological method of the Protestants.
Thus if one were today to propose a "Scripture only, but as interpreted by a Magisterium" model for theology, it would be immediately and roundly rejected by the Protestant community (except perhaps in a few small, radical sects) as being no true theory of sola scriptura at all. The term "only" in "Scripture only" must be taken not only to exclude other material principles of theology (like Tradition) but also other formal principles of theology (like the Magisterium).
But if one has cut loose the historic Christian principle of formulating the matter of theology into distinct, concrete doctrines then what is one going to use in its place? How is one to formulate doctrines if one has rejected what has historically been the formal principle? What formal principal will you propose in its place?
This was a question put by Catholics to Luther and the other Protestants, who answered that, in the absence of some group of Christians who were divinely commissioned with the task of formulating the material of theology, the individual himself must be divinely commissioned with this task. Thus the doctrine of an absolute right to private judgment—to deciding for oneself what the correct interpretation of Scripture is—was created.
Christians, of course, had always taught a right to private judgment—that the every individual had the right to think on and interpret the Scriptures for himself (this is why the Scriptures were read out loud at Mass, so that even the illiterate could hear them and think about their meaning). The exercise of private judgment was fine and wholesome and to be encouraged by all possible means so long as it was not used to reject those doctrines which had been determined by Christ's appointed teachers (the Magisterium) to represent the authentic teachings of the Bible.
Thus Christians had historically taught a right to private judgment, but not an absolute right that overthrew the teaching authority which Christ himself set up in his Church by gifting it with official teachers, as the New Testament itself declares (Ephesians 4:11). On any area in which the teaching authority of Christ's Church had not spoken (which was and is the great majority of areas), private judgment was permitted. It was only when a doctrine which had already been established to be true, such as the Trinity, the fully Divinity and humanity of Christ, the atoning death and resurrection of Christ, the efficacy of the sacraments, etc.—that private judgment was limited.
In order to throw off the Magisterium's teachings, however, the Reformers had to get past this limitation, and so they asserted an unconditional, absolute right to private judgment, according to which the individual had a right to disagree and to publicly teach contrary to even those doctrines that Christ's teaching authority had already established as true.
This was necessary as an answer to the Catholic question, "Who are you to overturn a historic Christian teaching which has already been settled by the Magisterium? You are not even a member of that body, much less the whole of it, and such doctrines can never change to begin with." In the face of this question, the Reformers were driven to answer, "We do not need to be the whole of the Magisterium, or even individual members of it, for every Christian has the right to settle every single doctrine on his own and is not bound in conscience to accept the rulings of the teachers which, we admit, Christ intended his Church to have."
Thus the doctrine of private judgment became a necessary component of the doctrine of sola scriptura. Scripture itself would be the sole material principle for theology, and the judgment of the individual would be the sole formal principle, as no other source could ultimately and authoritatively tell the believer what was the correct interpretation of Scripture. Any theory which said that there was a magisterial group of Christians who were to interpret the Scriptures on behalf on the individual would be vigorously opposed.
That is odd because, in several ways, that is exactly how the doctrine is applied in Protestant churches. Even though every member of the congregation has the theoretical right to interpret the Scriptures for himself, the vast majority of them do not.
There may, in any given congregation, be a number of theologically inclined people who make a serious study of the Bible, but the average person simply listens to the exposition given to the Scriptures in the Sunday sermon or weekday Bible study and accepts it. The pastor or Bible study leader sketches out what his view of the Scripture is, and it is not rigorously questioned by the average listener. The average person does not go out and get commentaries from opposing viewpoints, compare them to the pastor's view, and then do a rigorous analysis of the arguments on both sides.
(to be continued)