A few points.
First, no problem on misunderstandings. All’s well that ends well. :)
Second, almost all the major doctrinal deviations that occur are based on a departure from Sola Scriptura. Not the other way around.
There are two forms of said departure. Over-inclusivity and under-inclusivity.
Under-inclusivity is like the preacher who against all reason preach thus, “The Scriptures say, ‘Judas when out and hanged himself,’ and the Scripture also says ‘go thou and do likewise.’” The poor folks who end up under this kind of preaching will pay dearly for failing to address the whole counsel of God.
Over-inclusivity is also a rich area for error. You mention Oneness Pentecostals. They didn’t get started by Scripture Alone. In 1913 a man had an extrabiblical “revelation” about a special powers of a “Jesus Only” baptismal formula. One thing led to another and it ended up creating a movement to reject the Trinity. Go figure, but definitely NOT Sola Scriptura.
Other examples abound. Mormons => Book of Mormon. Jehovah’s Witnesses => Watchtower Society. Christian Science => Mary Baker Eddy, and on and on. No Sola Scriptura anywhere in sight.
On the other end of the spectrum, liberal decay of formerly decent denominations? Caused by outright rejection of the authority of Scripture. Big influence from the German School. The German philosophers are a useless bunch too. Definitely not Sola Scriptura. Not even close.
Baptist versus RC? What separates us are the doctrines we cannot find in Scripture. The rest of our unity does indeed come from our common respect for Scripture. The Arian controversy was fought and won on the basis of Scripture, not on the leadership of Rome, whose bishop had caved to the Arianism. The reason we both are Trinitarians today is because Athanasius clung bitterly to his Bible.
I’ve gotta go. Just keep in mind our models for Sola Scriptura can all be found in Scripture itself, Jesus in the Temptation, the Bereans checking Paul out, other examples, and there is no reason to think that humanism had anything to do with it. That is reading back into history things that are not there. The Reformation was, among other things, a sincere revival of interest in God’s word, delivered right to the doorstep of any average believer.
Riddle me this:
Private judgment is bad, right? Why? Because it introduces a fatal uncertainty in the conclusion. Great. So how do I escape private judgment to find my infallible interpreter?
By making a private judgment that I should believe some external claimant to infallible authority. Pick any authority. It doesn’t matter. In each and every attempt to escape the uncertainty of private judgment, I introduce the fatal uncertainty of a new private judgment.
Thus I am forced to wonder whether trying to escape from private judgment is even a good idea, since I seem to have no choice in the matter. It seems to be how God made me.
Then I discover that the Bereans were commended the Holy Spirit (through Luke) for their private judgment concerning Paul’s message, and I say to myself, whew, I can use the mind God gave me and let Him worry about keeping us all in line. Big relief, and it does work, though you and I doubtless mean something different by “working.” Subject for another post.
Gotta go.
Peace,
SR
Second, almost all the major doctrinal deviations that occur are based on a departure from Sola Scriptura.
Deviations according to whom; scripture according to whom?