Dang I posted the same definition for both LOL, Solo scriptura is the ONLY athority the way you think of sola now, not the supreme authority, sorry for messing that up.
Jimbone
I did understand what you meant, rather than said!
And, this is a big subject, so I will try to be brief.
First, it is true, that at least some reject all things outside scripture, so regard it as the only authority not just the supreme authority, without intending to pull punches, notupthome has repeatedly said the writings of fathers as uninspired , irrelevant, not worth reading.
Leaving that opinion aside,
The question is rather more nuanced and blurred, than you make it seem for several distinct reasons
First is interpretation. Most of our differences are interpretation, and it is hard for protestants to deny that their are multiple alternative interpretations , even just their side of the fence, take multiple interpretations of eucharist. Not that scripture is not authority but what does scripture mean?
To resolve the differences needs more than just scripture. Scripture does not self stand.
If then you go outside scripture in order to determine the meaning of it, sola scriptura becomes blurred .
Be it jewish custom, the tradition of the early church or even history that resolves it. Does sola scriptura still hold?
But it is worse than just differing interpretations of accepted things like eucharist,
Whether scripture even covers an issue of doctrine, can be a matter of interpretation too.
Without debating the issue pointing only at the argument of it, the "keys of the kingdom" as interpreted as the
office of steward in a davidic kingdom as per old testament has far reaching consequences, where some use the word keys in more modern context to deny it is an office.
So is the role of papacy there or not? The issue is not sola scriptura but interpretation of that and other scriptures
But beyond the issue of interpretation is also what is "necessary truth"
Assuming we all remove the absurd, that disciples breathed, and scripture does not say so, because it is not necessary doctrine, you are left with alltogether vexed questions.
Take a doctrine that launched 1000 arguments, the honorary title of "mary as queen", disregarding the historical context of that title used in Davidic times as a mother of a king. If we do not believe that it is necessary for salvation to honour her , but we do so anyway, then why do protestants bother to dispute whether it is in scripture or not?
If your regard sola scriptura as only "necessary truth"? Then if we regard it as not necessary, how does it violate sola scriptura? Ignore the example, see the generality. Deciding what is necessary is also a problem.
But that begs a further question.
If we hold that the didache defines in detail what scripture pointed in general, can you ignore the details of the didache, or other early church eg ignatius, so appoint bishops. So is that adding to scripture, or determining the meaning of it?
To another issue and equally vexed question. Is all that is in scripture necessary for salvation?
So from matthew 25 do we all have to visit those in jail? Was that an example? A commandment? Can we safely ignore it?
Does it matter which scriptures we hold as allegory? which we hold as fixed? Whether we hold them as meaning both?
Take the woman of revelations 12. Mary? Israel? Both? Is it necessary to believe one or more of them.
That we choose to take it literally, so picture mary with the moon at her feet? How is that not biblical.
So the definition of sola scriptura even as "necessary truth" becomes strained, and protestants have disagreed on it.
And so on.
But back to the main points I held. They apply to both solo and sola.
- That If scripture is supreme, or only authority that is a core truth of protestant belief.
If you hold that scripture contains the core truths, why is that of all core truths not there if it were true?
- How can solo or sola scriptura be true for first christians since they certainly not have scripture as we now have it, so the handing on of the faith (paradosis, tradition) was certainly word of mouth early on.
The objective reality is, to determine what the apostles passed on, you have to look at the early church to see how they interpreted it.
And only in that way can you resolve some of the interpretation issues.
We say you cannot take just scripture, and interpret it without information from outside, and history shows with all the divisions in protestantism what happens if you do.
So tradition history, and in our case the magisterium are needed.
But much of the problem that leads to the arguments is interpretation.