Douglas Campbell, author of The Deliverance of God: An Apocalyptic Rereading of Justification in Paul, has a helpful metric for discussing the rhetorical strategies we use to understand texts: over- and under-determination. Over-determination is where the text under consideration says something unhelpful or even contrary to what the claims based on it needs (think of how St James says "justification is not by faith alone" (2:24) and then look at the collective hand-wringing being done by searching that phrase in Google). Under-determination is where the text does not provide the necessary backing for the claims based on it. He makes a compelling argument in the book that the standard Protestant reading of St Paul and 'justification' is riddled with over- and under-determinations. The book (which is massive) is well worth a read, even if you don't end up agreeing with his conclusions. I'd like to use that metric to return to the topic of inspiration of the Scriptures, which I've written on before and will repeat some of the things I said there. (And, as always, I reserve the right to disagree with myself.)
The stereotypical argument concerning inspiration, at least as I learned it, went something like this:
A: The Bible is God's Word
B: God is Truth (or, negatively, God cannot lie)
C: Therefore, God's Word is true ("in all it speaks on" is a possible under-determination)
None of this is, for the most part, controversial (that the Lord Christ, member of the Trinity, is actually God's Word, from whom the Scriptures derive their authority, is an important point, but more is made of the difference between the two than is actually warranted). Also, none of this speaks a whit about inspiration. Inspiration is a teaching about the origin of the Scriptures, not their veracity or reliability. There may be correlations between the two topics, but they cannot, and so should not, be collapsed into one another. To do so would be to commit the genetic fallacy: the conclusion that the truthfulness of something is inherent in its origins. This particular fallacy has gotten lots of play in biblical scholarship over the years, especially in Old Testament studies with the Documentary Hypothesis; it also has a long life within the culture wars when we assume that if we have evolved from brute animals, we must be nothing more than animals (and do note that I'm not making any claims about this subject: it is beyond my ken).
It is possible, though, that even saying inspiration is a doctrine of textual origins is an over-determination. Once we clear out the texts about God's (and, consequently, His Word's and Spirit's) truthfulness, we have precious few didactic texts about inspiration itself. The main one is found, of course, in 2 Timothy 3:16: "All Scripture is given by inspiration of God..." Unfortunately, there is no parallelism, nor any explanation of the term used for inspiration, which happens to be, alas, a hapax legomenon. The term itself, θεόπνευστος, is a compound word from "God" and "breathing," so it could mean "God-breathed." Again, though, this may be problematic as compound words in all languages do not necessarily equal the sum of their parts. As this seems to be a word of Pauline origin (it is not extant in any other relevant ancient literature), it would seem best to look at how God's breath/Spirit is understood in the rest of the Scriptures. Here we find, of course, God's breath fluttering over the primordial Creation (Gen. 1:2), or the filling of Bezalel and Aholiab "in wisdom, in understanding, in knowledge, and in all workmanship" (Ex. 31:3 -- the connections between this passage and that of 2 Tim. 3 should not be overlooked), or His dwelling with -- and leaving -- the judges and the kings, or the famous passage in Isaiah 61 ("The Spirit of the Lord God is upon Me...to preach..."). God's Breath, then, is God's coming in power, especially in regards to the granting of words and wisdom. If we take this background back to 2 Tim. 3, we might see that the passage isn't speaking of origins, but rather how the Scriptures, bearing the Spirit of God, have power and authority: it is because they are a conduit of the divine Spirit that they can "make wise unto salvation...[be] profitable for doctrine, for reproof, for correction, for instruction in righteousness." Read like this, the passage is utterly non-controversial. It does not speak about how the Scriptures came to be (other places speak vociferously about that: "the Word of the Lord came to me..."), but about the power of the Word in the apostolic ministry.
That last clause merits some unpacking. The biggest under-determination of this text is using it divorced from its canonical context. While one of the beauties of the Reformation was its opening of the Scriptures to any literate person (and the subsequent drive for mass literacy that is only now waning in Western culture), it came at the heavy price of all Scripture being read flatly, as if all Scripture was addressed to everyone in the same way at all times, and, worse, led to Scripture being read outside of its necessary ecclesial context. An argument I heard while listening to a podcast called "Kingdom Roots," made by Scot McKnight, assumed that this text meant anyone picking up the Scriptures could utilize that power and be "trained in righteousness," etc. However, this misses the point that St Paul the Apostle is writing this epistle to St Timothy, the designated guardian of the Apostolic Deposit (2 Tim. 1:14, 3:14, etc.). For him who has "carefully followed my teaching, manner of life, purpose, faith, longsuffering, love, perseverance, etc." the power, the God-breathedness, of the Scriptures is made available to him for teaching (as a catechist), for reproof (as a pastor), for correction (again), for instruction in righteousness (note the chiasm), "that the man of God [those in St Timothy's care] may be thoroughly equipped for every good work" (3:16-17), or as St Paul put it elsewhere, "and He gave some to be apostles, some prophets, some evangelists, and some pastors-teachers, for the equipping of the saints for the work of the ministry, for the edifying of the body of Christ..." (Eph. 4:11-12). What tools do these gifted by the Spirit have for this work of equipping and edifying? The God-breathed Scriptures. Along with them, though, and inseparable, is that Apostolic Deposit, that way of life learned from the Apostles, what came by mouth or by letter (2 Thess. 2:15). There is no tension here between the Scriptures and the Tradition, for both came from the same Source: the Spirit given to the Apostles by the Lord Christ. The Church, which is the dwelling place of that selfsame Spirit, is the keeper of the Deposit -- which includes the Scriptures -- and the place where they must be properly understood and applied to the life of the believers in communion.
All this to say, and the true impetus behind writing tonight, is that we need to locate the Source of the Scripture's inspiration: the Spirit working through the Church. We over-determine 2 Tim. 3:16 in an attempt to ground sola Scriptura in Scripture, creating a bizarro circular argument in a text that was never meant to bear the weight of the Chicago Declaration. What is missing in the arguments about inspiration, precisely, is the Church herself. Inerrantists will be quick, in the face of all the text critical facts, to say that the Scriptures have been preserved from all error; yet the Church, the dwelling place of the Spirit (according to those Scriptures), is untrustworthy, fallible, corrupt, etc. What the doctrines of inspiration and inerrancy should make us do is to probe further our own understandings of what God is doing in history through His people, whom He has promised to indwell by His Spirit. The hard questions raised by post-evangelicals who have modified their views of Scripture based on the dilemmas and problems sola Scriptura and inerrancy (particularly) can be answered, but only as (paradoxically) we return to the Scriptures -- in their proper context, the Church -- and see what God has actually said about those Scriptures and the Church (and not just already assume our post-Reformation traditional answers).