The fact that “we” play fast and loose with a term on a frequent basis does not, then, support an argument regarding what is or is not discipline in a proper sense.
It’s not an argument. It’s an explanation. There is a difference.
Discipline is how we act; or the rules regarding how we act. Doctrine is what we believe. They are 2 different words and refer to 2 different concepts. Again, that is not an argument, it’s a statement of fact.
The term “mere discipline” means that it is only for the sake of good order but is not strictly-speaking required by the faith (ie required by doctrine).
It certainly doesn’t work on behalf of the argument that Sola Scriptura is merely a discipline when the reason for the “merely” is left up to the discretion of the user and “not a direct enforcement of doctrine or dogma.”
Here you’re taking different parts of the discussion and mixing them all together. I never said that the term “mere discipline” is left to the discretion of the user; nor did I write anything implying that.
As a Catholic, I believe that “Sola Scriptura” is an untruth. Therefore, I do not consider it doctrine or dogma. It is a false method of hermeneutics.
“Sola Scriptura” is A discipline. It is one form of thinking which is just one piece of a larger whole of a way of thinking or engaging in theology (or biblical study, etc).
For some groups of people, sola scriptura is both a discipline and a doctrine. As I said earlier, this applies to the evangelicals and fundamentalists. For a fundamentalist, sola scriptura is indeed a doctrine of theirs, which a Catholic would call a false doctrine.
For most Protestant denominations, sola scriptura is not doctrine by itself, but it is a method of discerning doctrine. And it must be noted that the method is not universally applied to all Protestants. Some (even non-fundamentalist denominations) employ it, some don’t.
Nor does it even address the reason why it might be reliable hermeneutic practice or discipline to begin with. Surely, it must be supported by some doctrine or dogma somewhere to attain the degree of influence or practice that it does. If it is “merely a discipline” then why would anyone base their entire exegetical approach upon it without any solid reason (i.e., some dogma or, at least, a sound doctrine) for doing so?
That last part is easy to address as a Catholic. It’s simply a false idea. I’m certainly not doing to defend it.