[boatbums]

That IS sola scriptura in PRACTICE, even though (I am well aware of the following fact I can assure you), that’s not the formal definition of sola scriptura.

You mean like with the formal Roman Catholic denial of "Catholics don't worship Mary", but, in PRACTICE, many DO?

The doctrine of sola Scriptura is that the Scriptures, as the sole Divinely-inspired resource we have, must be the basis for all claims of binding Christian truth. When someone asserts all Christians MUST believe XYZ, XYZ must be proved by God's word. This is an ancient principle going back thousands of years BEFORE Christianity even started. Isaiah the Prophet, for example, said:

And when they shall say unto you, Seek unto them that have familiar spirits, and unto wizards that peep, and that mutter: should not a people seek unto their God for the living to the dead? To the law and to the testimony: if they speak not according to this word, it is because there is no light in them. (Isa. 8:19-20)

[ronnietherocket3]

This is an ancient principle going back thousands of years BEFORE Christianity even started.And was taught by the Sadducees.

As for your Isaiah quote,

And when they shall say unto you, Seek unto them that have familiar spirits, and unto wizards that peep, and that mutter: should not a people seek unto their God for the living to the dead? To the law and to the testimony: if they speak not according to this word, it is because there is no light in them. (Isa. 8:19-20)

It does not say written law.

The doctrine of sola Scriptura is that the Scriptures, as the sole Divinely-inspired resource we have, must be the basis for all claims of binding Christian truth. When someone asserts all Christians MUST believe XYZ, XYZ must be proved by God's word.

At best this means that one cannot require belief in the Assumption; it fails to establish the Assumption is false.