... on Supreme Rule of Faith

Video:

Tour of the Catechism #4 - Relationship, Tradition & Scripture
franciscanfriars
https://www.youtube.com/watch?v=fuTSCFEETRo

I

"Sacred Scripture, taken together with Sacred Tradition [is] the supreme rule of [the Church's] faith."

From Dei Verbum, supplying words understood correctly from context within square brackets, otherwise quoting exactly from official translation, from #21.

Exactly. Meaning Magisterium in the present is the proximate rule. Meaning it can be licitly bypassed if betraying the supreme rule, at least by those sufficiently familiar with the supreme rule.

This means that any passage or aspect of many passages in Scripture, which Tradition has consistently taken as being literally true in their obvious sense, must be taken so and stand above Magisterium and Faithful alike in that precise way.

II

Of those who say Sacred Scripture is in its beginning to be understood as metaphors conveying truth but not accurate history, can their position be traced in accurate Church History from the Apostles and Our Lord Jesus Christ to us, and that in its entirety?

MSN Group Antimodernism in memoriam : One group member promoted Hutchison
antimodernisminmemoriam.blogspot.com/2014/03/one-group-member-promoted-hutchison.html

"When Our Lord Ascended to Heaven, He didn't leave behind a book, He left behind a Church"

Not quite. He left behind a Church equipped already with a book it got from those who had faithfully waited for Him and for His Church, namely the Old Testament. And he had during 40 days given a complete crash course of Old Testament exegesis, clarifying every allegory about Himself, about His Mother the Blessed Virgin Mary, about the Church, about their adversaries.

This might also have served, since allegory starts at verse 1 of Genesis, to indicate whether the text was only to be taken as allegory, or as factual history with an allegorical aspect added to it. Since nearly all Church fathers have taken it the second way, we must conclude that either He directly told His Apostles so, or He knew they already knew this and saw no need whatsoever to correct this as if their previous prejudice thereon were a kind of mistake.

And this was pointed out by the Biblical Commission of Pope St Pius X in 1909. Old Age Compromisers always cite Q 8 of the answer, how about looking at Q 2?

Creation vs. Evolution : Mark Shea Recommended David Palm Who Misconstrues Bible Commission of 1909
creavsevolu.blogspot.com/2014/01/mark-shea-recommended-david-palm-who.html

What is correct is that He left behind a Church of the New Testament which had as yet not written any books of the New Testament.

[But St Matthew was written 1 to 7 years after the last events. Oh, I already said that in the comment:]

3:35
It is traditionally rather often thought that St Matthew wrote his Gospel in a first version in Hebrew so it was published the year after that of Our Lord's Crucifixion, Resurrection, Ascension. Year 34, I have heard even. 

III

John 21:25, what can't it be used for?

Well, it would be difficult to argue that Christ told the Apostles:

a) to accept Evolution and Heliocentrism

and

b) still to include in his Gospel words He knew that Creationists would use and that without correcting explanation.

That would have been an instruction to duplicity.

Also, it can't be used to argue for Him telling His Apostles to accept Heliocentrism when it was proven, but say nothing on the subject and indeed leave OT passages arguing Geocentrism (which He knew would be used by Dominicans in San Marco in Florence to ring the alarm bell over Sidereus Nuntius), not to mention His own words considering the fact that footstools are often fixed in a place under the chair while one is sitting in such a one, because if that were the case how come Pope Urban VIII forgot it when Christ had promised the Holy Ghost would remind them of EVERYTHING he had said, including obviously what St John covered as not to be mentioned singly in one book.

John 21:25 what CAN it be appropriately used for?

Well, if St James was going to write on Penance and Extreme Unction, perhaps Christ was explaining in detail the Seven Sacraments.

If St Paul (or possibly St Barnabas) was going in the Epistle to the Hebrews to bring up that Christ was "priest" - sacrificial priest - "according to the order of Melchisedec", perhaps He had really given detailed instructions about what He meant with Hoc Facite ... In Meam Commemorationem.

Especially since the Sacrifice of the Mass, the Seven Sacraments, the Real Presence are not likely to be:

• Roman Catholic innovation after 1054 (though, just conceivably, Transsubstantiation as opposed to not thinking too much about details, might purely theoretically be so, but it may equally well be something really explained in detail to the Apostles);
• nor common RCC/EOC innovation after Chalcedon;
• nor even common RCC/EOC/Monophysite innovation after Ephesus.

And it CANNOT be a common Traditional Christian innovation after the Apostolic age, since according to Matthew 28:18-20 there can be none such. At least not harmful to the faith. Therefore not in any important matter.

Can John 21:25 be used about ANY matter of cosmology?

Well, He could have forestalled, at least for Rome, and therefore also Byzantium, a premature decision in favour of earth being flat.

[Pope St Zachary was from Byzantium, and was first prepared to condemn a round earth believer, but only because he thought there was a belief in antipodes involving non-Adamite men. THIS is severly forbidden.]

Jews and Nestorians seem to have made that mistake a matter of doctrine for centuries.

But Biblical authors as well as Tradition as a whole has not been tied down to Flat Earth.