Sola Scriptura: Death by a Thousand (or Ten) Qualifications?

July 3, 2011

by Doug Beaumont

Introduction

The doctrine of sola scriptura (“Scripture alone”) began its life as a concern for proper authority in religious matters. By “authority” here I mean something like “that which has the right to compel agreement.” A religious authority would be one which has the right to compel faith (orthodoxy) and actions (orthopraxy). This does not mean that one cannot make free choices in these matters, but simply that in cases of faith and action, a person’s refusal to agree with the authority would signal an objective wrong on the part of the one refusing to submit (should that person wish to remain in the religion at least).
It seems clear that all human authority in religious matters would be superseded by God’s. Now, since God is clearly the authority for a Christian, and since the only record of God’s communication that all Christian bodies believe to be inspired is the Bible, the Bible must have the top spot as far as authorities go. This was the original sense of sola scriptura – the Bible is the ultimate authority in matters of faith and actions – not that it was the only authority (cf. The Shape of Sola Scriptura or Getting the Reformation Wrong).
Why call it “Scripture alone” then? Because all of the Protestant “sola’s” are contrasts with what the reformers saw as distortions in Roman Catholic theology. Salvation through “Christ alone” (solus Christus) obviously did not mean that, given Christ, salvation simply followed. Rather, “Christ alone” meant something like “Jesus Christ, without the addition of something else [church, priesthood, etc.], is all that is required to make salvation possible.” The reformers taught that faith is also required of course – but not faith plus works (thus, sola fide). Sola scriptura meant that Scripture alone was the ultimate authority in religious matters as opposed to including Church tradition or the teachings of men.
While sola scriptura is still sometimes expressed along the lines of Scripture alone having “supreme and final authority in faith and life” (source), many evangelical Christians couch sola scriptura more in terms of denying any authority outside of the Bible. If Scripture alone is the ultimate authority, then it is thought that to follow that a “Bible-only” methodology for doing theology will keep one safe from the errors of mere human teaching. (For a treatment of the original, and more conservative idea, see Keith Mathison’s The Shape of Sola Scriptura – and for critical responses to this view see CTC or NLG). The first page of a Google search brought up two representative statements of this popular understanding of sola scriptura:
“Scripture alone is called God’s word (cf. Jn.10:35; 2 Tim.3:16; 2 Pt.1:20), and in 1 Cor. 4:6 we are specifically told ‘not to go beyond what is written.’. . . Not once did Jesus speak well about traditions. Neither did Peter nor Paul as he states in Col. 2:8 ‘Beware lest anyone cheat you through philosophy and empty deceit, according to the tradition of men, according to the basic principles of the world, and not according to Christ.’” (Source).
“The only way to know for sure what God expects of us is to stay true to what we know He has revealed—the Bible. We can know, beyond the shadow of any doubt, that Scripture is true, authoritative, and reliable. The same cannot be said of tradition. The Word of God is the only authority for the Christian faith. Traditions are valid only when they are based on Scripture and are in full agreement with Scripture. Traditions that contradict the Bible are not of God and are not a valid aspect of the Christian faith. Sola scriptura is the only way to avoid subjectivity and keep personal opinion from taking priority over the teachings of the Bible.” (Source)
But can Evangelicals consistently reject extra-biblical authority? As will be made clear below, I do not think so. Bible-alone theology may sound very fine when constrained to an abstract ideal, but as Antony Flew once said, a good hypothesis can “be killed by inches, the death by a thousand qualifications.”
Even allowing that the Bible is the final and ultimate authority for Christian faith and practice, it still must be understood. That is, the Bible’s authoritative teaching resides in the message it conveys – not the physical book itself. And discovering the message of the Bible requires navigating through many layers of human interaction first. These layers of human interaction are like lenses through which the Bible’s message is seen. It seems to me, then, that to whatever degree these interpretive layers influence how one understands the Bible’s message, to that degree they have an authoritative function (at least practically speaking). This seems to introduce the very kind of human authority that the popular sense of sola scriptura claims to avoid. Below are presented ten such layers for consideration.

Linguistic Layer

The average-Evangelical-in-America-today often thinks that he “just believes his Bible” when it comes to his religious convictions. But if you asked him, “What exactly is the Bible?” he would probably answer, “The Word of God.” But the Bible he is holding almost certainly does not contain the literal words of God – at least not how he is probably thinking of them. Let’s begin here, for one important layer of authoritative reliance required for today’s Bible-believer is linguistic.
The Bible is actually a bound collection of writings written in three ancient languages: Hebrew, Aramaic, and (Koine) Greek. Since our average-Evangelical-in-America-today does not understand these ancient languages fluently, the Bible he holds is almost certainly a translation of the words of God. But there is a plethora of Bible translation “versions” on the shelf of the average book store, and translation issues are not always minor. For example, are we to “abstain from all appearance of evil” as the KJV has it, or are we to “abstain from every form of evil” as modern versions state? And try looking up Matthew 17:21 or 23:14 in the NIV sometime!
So how did our average-Evangelical-in-America-today choose from among them? Was his choice authoritative? And if so, was he operating as his own authority in the matter? Or, assuming he researched these versions, would not the source(s) he consulted for his decision have, in a sense, authoritatively determined what he is going to read in his Bible? Further, how were these authorities chosen? What if they were wrong? And how could he ever find out?
Suppose our average-Evangelical-in-America-today decides that trusting some extra-biblical authority to pick his Bible version is not a safe practice – for sola scriptura says no authority outside Scripture is trustworthy enough for such a decision. There seems only one way to solve the problem: stop relying on them. The only way he could authoritatively choose the best Bible version without invoking the authority of mere men would be to become an authority himself. That is, he will have to become an authority on the original languages for himself. But, of course, any teacher of biblical languages will herself be another extra-biblical authority. In fact, it is authoritative linguists that (hopefully) were responsible for the different Bible versions themselves. But if these authorities cannot be trusted to produce trustworthy Bible translations, how can they be trusted to teach others how to do so?
Further, how long will it take to achieve an authoritative linguistic status? Given the training available at many schools, 7-10 years is probably wildly conservative (and that’s if one does not add in Aramaic and any other cognate languages that factor into translation). This also assumes that our average-Evangelical-in-America-today can study full time.

Translational-Interpretative Layer

However, even after learning vocabulary and grammar, the fact is that words do not change into thoughts without interpretation. Even if our average-Evangelical-in-America-today learns the original languages, this does not mean that interpretation is not part of the process of translation. Translation involves far more than simple word replacement. Just like in English, the biblical languages do not come with neat, immutable dictionaries. Even theologically significant words like “save,” “justification,” “sanctification,” and “resurrection” are not always used the same way in Scripture.
To really translate the original languages correctly, one must be familiar with how that language was used at the time of the original writing. To do so, the other writings of the same chronological, geographical, and cultural background must be studied. Indeed, this is how the standard lexicons derive their data. But who can know which lexicon to trust? Biases come into play with lexicons as well (consider BAGD’s treatment of glossa where, after noting the term simply means “languages,” there is suddenly “no doubt about the thing referred to, namely the broken speech of persons in religious ecstasy”). Further, room must be left for linguistic innovation. The Bible was written in living languages, thus it is entirely possible that subtle usage changes were being made that are lost on later readers relying on typical usage.
But again, for sake of argument let us stipulate that our average-Evangelical-in-America-today has somehow overcome these issues too. After gaining unbiased insight into linguistic usage that even experts might have missed, he now needs to consider an even more difficult interpretive issue.

Hermeneutical-Philosophical Layer

Language and translation study may give our average-Evangelical-in-America-today knowledge of what ancient texts say, but understanding what they mean is another issue.
Hermeneutics is the science of interpretation of meaning. Is there an over-arching hermeneutic that works for the whole Bible? Do we simply take all words literally (at “face value”), or are some non-literal understandings actually more accurate? Literal hermeneutic theory might seem safest, but of course this will obscure any non-literal texts. The ancient Church had a four-fold hermeneutic. They believed for centuries that the Bible had literal, allegorical, moral, and analogical senses. While this four-fold hermeneutic is often decried today, consider the difficulty faced in taking many of the prophetic fulfillments of Jesus’ birth with a literal/grammatical/historical-only hermeneutic (e.g., Isa. 7:14 cf. Mt. 1:18-25; Jer. 31:15 cf. Mt. 2:16-18; or Hos. 11:1 cf. Mt. 2:13-15). Non-Christians have field days with the original “intent” of these passages and their alleged misuse by the gospel writers.
Few seriously argue that Scripture can be taken in a purely literalistic fashion, for at least some of the Bible is poetry, metaphor, hyperbole, etc. But recognition of these things requires extra-biblical knowledge – for the Bible itself does not always signal these elements. So, in many cases, hermeneutics becomes philosophy of language. But the Bible is not a useful source for coming to one’s philosophy of language either, for one must already have a philosophy of language before the Bible can be interpreted!
Further, literary devices like hyperbole and metaphor rely entirely on one’s experience of reality to recognize. But reality, too, must be interpreted. Thus, correct notions of metaphysics are necessary if we are to avoid subjectivity in biblical interpretation. Thus, one must get one’s metaphysics and linguistic philosophies correct before hermeneutic theories can be properly evaluated or applied. Either philosophical field could easily take up a lifetime.
But let us allow for super-human accomplishments on the part of our average-Evangelical-in-America-today, and grant that perhaps his view of reality and language are exactly correct, and his views are completely uncluttered by inaccurate understandings of his personal experiences. The authorities involved in such pursuits (even if they include only the philosopher himself) are going to once again be mostly (if not entirely) extra-biblical.
And the work is not over yet.

Historical-Cultural Layer

Abstract language meaning might be objectively understood via a proper hermeneutic, but its specific referents can remain unknown. The particular realities that words pick out are not shared by the biblical writers and our average-Evangelical-in-America-today, for they are thousands of years, and thousands of miles, removed from one another.
Sometimes important cultural details are sometimes lost to history. For example, what exactly is the “head covering” Paul refers to in his letter to the Corinthians, and what was its purpose? What is this “baptism for the dead” Paul refers to in the same letter, and what was its purpose? Mere knowledge of language, even coupled to a good hermeneutic, cannot answer these questions. And sometimes we do not even know a question should be asked. When Jesus warns the Laodiceans to be either hot or cold, not many later readers recognized the import of those two temperatures to a city without its own water supply.
A thorough knowledge of history and culture is necessary to avoid anachronism and other such errors, and to catch subtle remarks that the original readers would have recognized. In the New Testament, for example, we come upon scribes, Pharisees, Sadducees, synagogues, and a Roman Government without much introduction or explanation in many cases. Yet none of these are known from the Old Testament. The Bible causes these issues, it does not solve them. But to whom can our average-Evangelical-in-America-today go to learn about these things if not extra-biblical authorities? Unless, of course, he simply becomes an expert on history on his own. A time machine (coupled with an anti-aging device) perhaps?
Assuming that our average-Evangelical-in-America-today somehow (miraculously?) manages to meet the above criteria, the job is still not done. For once one knows what a text says and what it means, one must then grasp what it teaches.

Applicational Layer

After discovering what a text says and what it means, it is time to get something out of it. Application answers the question, “What is the text teaching?” Here we run into more examples of Scripture not supplying easy answers.
Do the stories of people speaking in tongues in the Book of Acts teach us that believers today must do likewise? Is the head covering in 1 Corinthians a practice that has some parallel today? Does the acceptance of slavery throughout the Bible indicate that it has an acceptable place in the world today? Why do we practice the Lord’s Supper but not foot washing when Jesus commanded both during the same talk? These sorts of questions cannot be answered simply by knowing what the Bible says or means.
Discovering how the truths of Scripture apply to us today is the whole goal of Bible study – yet the Bible is rarely clear on just how to do so. Many disagreements over Christian practice do not involve issues of translation or interpretation, because knowing what the text means does not necessarily tell us what it teaches. Even in cases of prescription (rather than mere description), issues of cultural relevance, proper dispensations, audience similarity, general vs. particular commands, etc. all remain. Now subjects such as ethics, moral philosophy, theology, and others come into play. And, since it is the Bible that seems to raise the above issues, it seems that once again extra-biblical information is required.
But what if our average-Evangelical-in-America-today sought this extra-biblical information from God rather than man? Wouldn’t that solve the problem? It depends on who you ask.

Mystical Layer

The “mystical” layer is unique to this list in that it is both more and less controversial than the others – especially when it comes to authority. On the “less controversial” side, I think most Christians will agree that without the aid of God, the Scriptures cannot be fully “grasped” (I am being purposefully vague in order to make the statement general enough to be true). Now, whether this help comes in the form of direct explanation of textual meaning, divinely inspired objectivity, subjective personal application, or any of a host of other explanations – God is doing something when the faithful read His word.
The difficulty is the “more controversial” part. For one thing, there are a number of views concerning God’s role in interpretation (sometimes called “illumination”). Some believe that God only steps in to call the “close ones,” while others think they are getting a live feed from God’s mind via the pages of the Bible virtually every time they open it. In either case (and for any in between), if the Bible itself cannot settle a given view, then claiming that God’s aid sealed the deal would be to invoke divine authority for one’s own understanding. The result should be the very kind of extra-biblical authority that sola scriptura seems to seek to avoid. Further, to whatever extent God is helping out, that part of the interpretative process would seem to be free from error. But few will allow (whether theologically or pragmatically) for any infallibility being introduced into the process. For most this would smack of either infallible Catholic papal claims or charismatic prophetic craziness – neither of which comport with sola scriptura.
A more difficult fact to deal with is that while the Church underwent one or two important splits in its first 1,500 years, “sola scriptura Christianity” has managed to break itself into more than 20,000 denominations in the last 500. If God’s guidance in some way insured some allowable extra-biblical authority in understanding Scripture, then how could it be fairly determined which denomination (or, in many cases, which individual) has it? It all sounds very impressive when a preacher or teacher challenges his hearers to check his words against the Bible, personal study, or prayer – but with the abundance of interpretive options awaiting the researcher (consider, for example, the popular “multi-view” book series put out by more than one evangelical publisher), this challenge is hardly threatening.
I will leave additional theological issues with the mystical layer aside, for they do not necessarily help or hinder either side in the present consideration of sola scriptura. For now it is enough to note that whatever role God plays in the process of biblical interpretation, it does not seem to get what is needed to avoid extra-biblical authority. Even if a non-question begging sola scriptura theory of (and evidence for) mystical illumination were forthcoming, the chaotic theological results are not easily explained.
Our average-Evangelical-in-America-today will not, therefore, be able to trust in personal mystical guidance and follow sola scriptura at the same time. So for now, let’s just get back to the Bible – the one source we know we can trust.
If, that is, we really have one.

Textual Layer

Supposing that our average-Evangelical-in-America-today learns the original biblical languages so well that he can pick up an original Greek New Testament or Hebrew/Aramaic Old Testament and read it as easily as he can an English translation. He has overcome all interpretive and philosophical biases, and has learned enough about history and culture to catch every nuance that an original reader would have. He is also accessing God’s mystical guidance (if it is available) without distortion. No more “Bible versions” for this average-Evangelical-in-America-today, right?
Wrong.
Unfortunately, the Bible version issue does not disappear once one masters the original languages. Now he must also choose which “original Bible” to read. For the New Testament alone he must choose between the Minority and the Majority text traditions (and there are different versions of each of these forms, such as the Nestle-Aland or the United Bible Society’s, or the Textus Receptus – each having had numerous revisions). The Old Testament, too, has some textual issues – the most notable being that the Hebrew manuscript copies (the “Masoretic” texts) that we have are much later than the original writings. There is also the Greek translation of the Old Testament (known as the Septuagint, or “LXX”) which is quoted more in the New Testament than the MT, yet sometimes differs considerably from the Hebrew texts we have.
Arguments for each of these versions abound, and have spawned their own fields of study commonly referred to as Textual Criticism. Textual Criticism deals with issues arising from the fact that we do not have the original manuscripts of the Bible. What we do have are thousands of copies, some very early, that must be sorted through and compared for accuracy. As skeptics are happy to point out, few of these manuscripts agree completely. Now, this is not such a huge problem since given thousands of comparisons we can arrive at a pretty solid understanding of what the original must have said. But differences (“variants”) remain, and questions need to be answered when it comes to deciding which variants to use when producing the “original” edition. In how many manuscripts does the variant reading occur? What are the dates for these manuscripts? In what region of the world were these manuscripts found? What could have caused these varying readings? Which reading can best explain the origin of the other readings? Etc.
A lot of work, then, is needed just to produce an accurate original language Bible (assuming, of course, that the original wording has indeed been retained amongst all these disparate copies). How is our average-Evangelical-in-America-today going to choose between them? Well, unless he is willing to trust in the text-critical authorities, he’ll have to learn text criticism itself. Worse, unless he wants to trust in the people who typed up what is actually found on these ancient manuscripts, he’ll have to gain access to all of them directly, from all over the world, and make his own copies. To do otherwise would be to trust extra-biblical authorities (besides himself) with copying the words of God.
But let’s cut our average-Evangelical-in-America-today some slack and say that he does somehow gain the true perspective on text criticism and obtains his own copies of all available manuscripts. How long will it take to go through all these copies? Professionals spend their entire careers working on mere subsets of these document collections. This pushes the possibility of avoiding extra-biblical authority even farther from the already outrageous situation we have already granted to our average-Evangelical-in-America-today.
And speaking of collections – why does our average-Evangelical-in-America-today trust anyone to tell him which books he should even be including? Welcome to the canonical layer.

Canonical Layer

Despite what our average-Evangelical-in-America-today may have at once thought, he now knows that the Bible is not “a book.” Rather, it is a collection of various writings that are bound together for convenience. But who decided which books are in this collection? And how did they do so?
The official title of the biblical collection is “canon.” Now, the canon of Scripture did not begin to be solidified until the 3rd or 4th century. The Church was teaching from both oral and written traditions before that time, holding authoritative councils, writing the creeds that would determine Christian orthodoxy, and using all of these in the process of canonization. Thus, ironically, it would seem that to ignore this early extra-biblical tradition might also justify ignoring the biblical canon itself.
Is the average-Evangelical-in-America-today just as free to jettison the biblical canon as he is the traditional Church creeds and councils? Would an average-Evangelical-in-America-today feel free to dismiss certain books of the Bible if they did not sit well with him? Would he be free to add to the canon should he “feel led” to do so? If so, what is the standard by which he could or could not do so? And how would these arguments work with or against extra-biblical Church authority?
Numerous tests for canonicity have been suggested to avoid this problem, but many of them are the result of a-historical attempts at “reverse engineering” the canon. Tests include: evidence of inspiration, proper spiritual character, church edification, doctrinal accuracy, apostolic authorship or endorsement, general church acceptance, etc. The problem is that several of these rely on subjective criteria, others are objective but rely on the testimony of extra-biblical tradition for their evidence. To take just one example: the criterion of apostolicity relies on knowledge of who wrote the book in question and / or the author’s relation to an apostle. But several NT books do not name their author (e.g., the Gospels and Hebrews), and others are vague (e.g., James, Revelation). Moreover, even the books that do name their authors can only be trusted as far as they are deemed trustworthy in the first place. The Church did not accept the gospels of Thomas or of Mary – why not? The facts are that the members of the Church closest to the time of the apostles disputed the content of the NT canon, and that this disputation continued well into the Reformation (on both Catholic and Protestant sides), and disagreements of varying degrees continue right up to today. Thus the escape from extra-biblical authority sought by these tests is often lacking.
Now our average-Evangelical-in-America-today faces a critical dilemma: he’s spent years learning the languages, figuring out the best text-critical theory, and somehow obtained his own copies of all the relevant manuscripts – but he still has to trust extra-biblical authorities to even know which books belong in the Bible in the first place. But let us simply suppose once again that our average-Evangelical-in-America-today gets this one right. He nails the canon and somehow justifies his choices without any appeal to extra-biblical authority (perhaps he uses Calvin’s test of self-authenticating testimony . . . which of course is also extra-biblical). Is he done? Can he now be sure of his Bible’s teachings without relying on any outside authority?
Hardly. Indeed, he has only begun.

Traditional Layer

If the Church’s traditions are not considered authoritative, then not only are its biblical interpretations and extra-biblical teachings called into question – but so might its councils, creeds, and the canon of Scripture itself. For whatever arguments serve to create distrust in the authority of the early Church also makes other areas of orthodoxy open to criticism, and how can sola scriptura survive if we cannot be sure of what counts as “scriptura” in the first place? But many claim that the whole point of sola scriptura is to avoid traditions! Isn’t that what gets the Church into trouble in the first place?
Does Scripture teach the faithful to mistrust tradition? No, it does not. Rather, it warns of following false traditions (just like false philosophy, false religion, etc.). It’s the “false” part that is important. Claims such as the ones mentioned in the introduction concerning Scriptures’ alleged negative outlook on tradition must simply ignore other verses to remain consistent (which is made easier by the NIV translators who purposefully translated the Greek term paradosis as “traditions” in its negative contexts, and as “teachings” in its positive references!). For example, the same apostle who warned against following man-made traditions also said:

“Therefore, brethren, stand fast, and hold the traditions which ye have been taught, whether by word, or our epistle”
(2 Thessalonians 2:15)
“Withdraw yourselves from every brother that walketh disorderly, and not after the tradition which he received of us”
(2 Thessalonians 3:6)
“Now I praise you, brethren, that you remember me in all things and keep the traditions just as I delivered them to you”
(1 Corinthians 11:2)

Now, to be absolutely sure of one’s understanding of Christian doctrine from the Bible alone, at least three things must be the case:

1. First, authoritative tradition must have ceased with the apostles (to avoid the self-defeating proposition that the Bible – which teaches that traditions must be trusted – alone is trustworthy).
2. Second, the Bible would have to be perfectly clear in what it teaches (to avoid any possible misunderstanding, each part would have to have this clarity – for if it did not it may be the case that one part would alter another).
3. Third, everything the apostles wanted taught must have been recorded in Scripture (because the slightest bit of additional information could radically alter our understanding of anything else we read).

The first two points seem to be self-evidently required, but the first begs the question and is self-defeating because the Bible does not teach (at least not clearly) that authoritative tradition ceased with the apostles. If this is one’s theological position that is fine (and the theological layer is coming up!), but it must be recognized as such. As to the second criterion, the numerous and disparate interpretations of Scripture offered by the very people who proclaim its clarity seem to argue against that position. If one responds that proper hermeneutics/philosophy/ etc. are required to attain this clarity then we are back to additional layers of interpretation. The third point is even more seriously problematic for sola scriptura as it has been popularly defined, however. For even if Church tradition after the apostles is not authoritative, and even if Scriptures are perfectly clear, it would only have taken one extra sentence to change everything.
As an example, let’s consider communion (the Lord’s Supper / the Eucharist). Paul told the Corinthians concerning communion, “the rest I will set in order when I come,” (1 Cor. 11:34). Suppose that what he later said to them was, “By the way, Jesus Christ is physically present in the communion bread and wine.” That one sentence would be a game changer for interpretation of not only 1 Corinthians 11, but for John 6 and Matthew 26 as well! Now, we do not seem to know what Paul “set in order” concerning communion when he came to them later. 2 Corinthians says nothing about it. Paul does mention two other letters to the Corinthians that we do not have, so perhaps it was in those. Or maybe in the epistle that he sent to the church at Laodicea (Colossians 4:16) he said something of interpretive importance. Either way, it did not make it into the Bible – and to be 100% certain of his Bible-only understandings, our average-Evangelical-in-America-today would have to know for sure.
What we do know is that the Church held to a non-memorial-only view of communion for nearly 1,500 years. This view might not be clear from Scripture, but it is no less clear than Zwingli’s memorial-only view. How can sola scriptura solve this debate then? The same could be said for the Bishop/Elder distinction – this does not seem clear in Scripture, but it was recognized very early by the Church whose leaders were taught by the apostles. For the average-Evangelical-in-America-today, however, the early Church is not considered an authoritative source. So its tradition cannot be trusted to authoritatively solve the problem. This remains a problem even if some new bit of information surface, for these would be extra-biblical too.
Thus, even if our average-Evangelical-in-America-today can successfully demonstrate that no extra-biblical tradition is authoritative unless it accords with [his understanding of] Scripture, the issue remains. Judging extra-biblical tradition based on the Bible when the Bible is unclear is going to be a failed project. Yet for our average-Evangelical-in-America-today, it seems to be all he has to go on. Worse, in cases where extra-biblical traditions could legitimately overturn a Bible-only interpretation, then a Bible-only approach would never – even in principle – be able to authoritatively judge against extra-biblical tradition (for even apostolic teaching is extra-biblical if it did not make it into the Bible). Since such a situation is certainly possible, then given a Bible-only methodology, our average-Evangelical-in-America-today could only hope to arrive at probable interpretations. He would remain, ultimately, unsure of a great many things.
Now, mere logical possibility does not equal actual evidence. Perhaps arguments can be produced which support a contrary position, but since the Bible does not contain them, they are extra-biblical too. This should cause a problem for the popular view of sola scriptura, for these sorts of positions turn out to be not so much biblical as theological.

Theological Layer

Since the Bible does not say that it alone is trustworthy or authoritative, the idea that it is so is a theological one. In many areas holding to theological positions that are not clearly stated in the Bible is not necessarily a big problem, since many positions are based on theological speculation. Here, however, it becomes a bigger issue.
It would be incoherent to claim that the Bible alone is a trustworthy source of theological information when the Bible itself does not say that it alone is a trustworthy source of theological information. In addition, it would also turn out to be self-defeating since the Bible itself teaches that other sources of revelation exist (e.g., the principles of natural theology and law found in Rom. 1-2). And, since the Bible actually commands believers to hold to “traditions” that they “heard” (see above), it simply cannot be the case that the Bible’s position is that traditions do not become authoritative until they are written down. Something like this might be argued theologically, but it is not a teaching directly supportable from the words of the Bible. The same could be said for limiting authoritative “traditions” to the words the Apostles left us in Scripture – this is not what the early Church taught, and it pre-dated the New Testament itself.
But even our average-Evangelical-in-America-today (who stopped being average a LONG time ago!) could defend these theological positions, some extra-biblical authority is in the picture – for the Bible does not teach them directly. Even doctrines said to be derived from Scripture are still adding something to the mere words of the Bible and are, to that extent, extra-biblical. And once again, although attractive in the abstract, the ideal that theology can be directly supported from Scripture alone and achieve the authority the Church desires is a position held by the very theologians who disagree the most over theology! (Consider the popular Counterpoints series.)
And this brings us back to the original problem.

Conclusion

Bible-only theology sounds fine as long as it remains an abstract principle (or slogan). The reality is much messier. At least the following authoritative layers would need to be peeled back before a strict Bible-only theological method could even theoretically succeed:

1. Linguistic – to avoid having to trust non-authoritative translators.
2. Translational-Interpretational – to avoid having to trust non-authoritative interpreters.
3. Hermeneutical-Philosophical – to avoid having to trust non-authoritative philosophers.
4. Historical-Cultural – to avoid having to trust non-authoritative historians.
5. Applicational – to avoid having to trust non-authoritative teachers.
6. Mystical – to avoid having to trust non-authoritative personal views.
7. Textual – to avoid having to trust non-authoritative text critics.
8. Canonical – to avoid having to trust non-authoritative Church decisions.
9. Traditional – to avoid having to trust non-authoritative traditions.
10. Theological – to avoid having to trust non-authoritative theologians.

In the real world, reliance on extra-biblical authority is found at nearly every step of Bible study. Even if our average-Evangelical-in-America-today had the time, materials, and intellect for such an endeavor, he would still realistically have to rely on a host of extra-biblical authorities (teachers, authors, researchers, principles, etc.) to learn all that he would need to know to become a trustworthy [yet extra-biblical, and thus still fallible!] authority himself.
As stated in the introduction, it seems to me that to whatever degree these layers of human interaction influence how one understands the Bible’s message, to that degree they have a practical authoritative function. (Perhaps independent tests are available to assess each layer’s authoritative status without engaging in question-begging or misplaced confidence. If so, then these need to be spelled out more clearly.) Thus, it seems clear that the Bible in our hands can only be depended upon to deliver authoritative truth to the degree that the authorities at each layer can be trusted to deliver authoritative truth.
Now, if sola scriptura is understood as simply teaching that the Bible “alone is of supreme and final authority in faith and life,” then these problems may be avoided, for this would at least admit to the possibility (if not the necessity) of additional authorities. Under this view, sola scriptura can operate alongside extra-biblical authorities without necessarily placing any of them at a level that the Bible alone occupies. The pertinent question then becomes when these authorities can be considered trustworthy (when they are considered at all).