One of the reasons that Catholics give for why sola Scriptura is invalid is the idea of the inadequacy of private interpretation of the Scriptures. This inadequacy seems apparent, especially given our relativistic modern culture. But in this case, the seemingly “obviousness” of the inadequacy of private interpretation ends up being a shell with no center.
The first thing that should be looked at is the philosophy invovled. What is interpretation? For a loose definition, let us call interpretation: the method by which the original meaning of a statement is attempted to be understood by a second party.
So if I wish to communicate concept X, I can write propositional statements about X. A second party (i.e. anyone who is not me) then reads those propositional statements and uses interpretation to figure out what I mean by concept X.
Interpretation, therefore, involves the system of linguistics. In order to convey a message from myself to another, I must employ the use of language. In this case, I use the English language as it is the language I am most fluent in, and also the language of those whom I intend my message to go to.
How does language work? It involves conventional definitions of terms that are used by everyone in the same manner. Naturally, relativists point out that no one can use the terms in exactly the same manner; but since most terms are related to our experiences, and human experiences are by and large universal experiences, we can have a universal language the is more than sufficient to convey meaning from one person to another person based on references to those common, objective experiences.
Interpretation, therefore, involves the use of these linguistic norms to come to an understanding of someone’s intended meaning. In order to interpret something, one must be able to understand the terms used, the context of the language, and the universal aspects that those terms appeal to.
All this is done without much thought through the common use of language. For instance, English readers can comprehend what I write in this sentence without thinking about how they define any particular word in this sentence. The definitions work behind the scenes as a reader pulls from their pool of words and terms and assign the meaning to those words, as well as the common sense attempt to synthesize meaning of words into the context provided by the other words.
Therefore, people are able to understand what I write by employing the rules of grammar and syntax, all without consciously doing so. This, then, I call the “ordinary means” of interpretation. It is ordinary insofar as it is universal and it is done without conscious effort.
But it is still the case that using “ordinary means” to interpret my writing is, in itself, a private, personal interpretation. You do not have access to my mind to know what nuances are carried by any particular word that I use; but you do have the common use of the terms to guide you. You use your private interpretation of what I write to come to a conclusion on my statements.
Now the strength of the Catholic argument is in the fact that personal, private interpretations can often be wrong. One might not read carefully what I have written. Futhermore, one might not know the definition of a specific word that I use. Or one might have mis-learned a defintions; or I might have done so. Thus, when one reads what I write, it is possible for error to creep into one’s personal interpretation.
But is this a problem with what is written? Only insofar as I mis-use specific words. If I use words correctly (according to convention) then there is no problem with my words, but instead the problem lies in the one who has misunderstood the words. In such a case, those who understand my words correctly can correct the one who misunderstands my words by pointing to the conventional meaning of the words.
This works even if I mis-use a word, for one can look at the context and determine what a term must mean. One can then appeal to the context and previous uses of the same term to make an argument as to what I intended to convey by the use of the term.
In each of these instances, one is using a private, personal interpretation; but it is not one that is isolated on the individual! It is one that conforms to the norms of “ordinary means” of interpretation. One does not need to specifically ask me to clairfy points that are clarified within the text I write. The only time one would need to ask for clarification is if the information needed to understand what I write is not present in my written materials. For example, if I use a term only once and it is not clear from the context what exactly it means, one would be justified in asking me to provide clarification.
This is what Roman Catholics say the Magisterium is designed to do. When there is confusion in the text, the Magisterium has the “Tradition” that can interpret these words correctly.
When someone interprets what the Magisterium says, however, that person must still use his personal interpretation of the Magisterium. The personal interpretation filter merely moves back one step. Now, instead of interpreting the original text of Scripture, one must interpret the meaning of the Magisterium. This, too, is prone to exactly the same kind of errors as any text of Scripture, because both the text of Scripture and the statements of the Magisterium are based in language.
But there is a second problem.  Stating that Scriptures require that Magisterium for interpretation presupposes that these answers cannot be found in Scripture already. It presupposes that the Magisterium is necessary because the text of Scripture is insufficient to provide meaning. In other words, the Magisterium is required only because Scripture is lacking.
The Protestant view, on the other hand, is that people, using ordinary means, can indeed understand the salvific nature of Scripture. This does not mean that a reader will understand everything in Scripture; there surely are some issues that are too vague or too planted in a previous culture for us to understand completely. However, when it comes to the message of the Gospel, the message is simple and repeated several times so what is unclear in one passage is clear in another passage. Therefore, using ordinary means and reading all of Scripture, anyone is able to know what is necessary for salvation.
Does this mean that Protestants think it should be “every man and his Bible alone”? Of course not. God gave us the church for a purpose and a reason, and part of that was to ensure correct doctrine. Naturally, churches can err since they are made of fallible people, but the tendancy of the church to err is going to be less likely (due to the correcting influence of other perspectives present there) than a person on his own (with no other perspective than his own). The church–the assembly of believers–while not infallible, is still important. The opinions of others, while not infallible, are still something that should be considered.
However, in the end, regardless of what anyone else says, what you believe is going to be what you personally interpret to be truth, whether you get that truth from other people or from the Scriptures themselves. There is simply no way to avoid the personal aspect of this, since at the point of personal belief there must be a personal interpretation.
