We have before us a factual question: which method did God choose to hand down his word authoritatively and normatively through history? Is it by (a) the preexisting view of the CC (and EOC) at the eve of the Reformation, i.e., God established that His word is transmitted by the united and interrelated process of Scripture and Apostolic Tradition in the Apostolic Church (=STC); or (b) or the newer method proposed by the Reformers, sola scriptura (=SS)?
Truths for a fair sola scriptura discussion with Catholics.
(1) The teaching of the CC was (and is) that the CC is continuous (and has always held itself to be continuous) with that of the Apostles at Pentecost and likewise the tradition it handed on. Unity and continuity are inherent in STC as understood by the CC at the time.
(2) The Reformers protested against STC claiming rather that Scripture is the sole rule of faith (=SS), and based on this, that the Church and councils have erred, and CC has not preserved apostolic tradition or its own apostolic continuity, but rather has departed from it.
Luther and Calvin explicitly offer arguments against the preexisting view, STC. That is, given that the Reformers tenants were newer than the preexisting view, they had (and did assume) the burden of proof in this matter.
(3) In arguing against STC the Reformers set the results of their interpretation of Scripture alone over against that of the existing Church and Tradition and the faith thus transmitted, that is, over against the content transmitted by STC including STC itself.
(4) Any definition of the CC’s position by Protestants for purposes of discussion and evaluation must, to be fair, include the unity and continuity of STC.
So, for example, to say “the CC accepts Scripture but believes that one must add to it by tradition and its own decrees” is not defining what the CC believes. Such a definition would at least be evaluating and interpreting STC by means of SS if not simply rephrasing SS.
(5) Any attempt to check for SS versus STC in the fathers and Ecumenical Councils must include their doing what the Reformers did in (3) above.
So for a father or Council merely to assert that Scripture is probative or that every conviction must be tested by Scripture would not constitute SS. SS must include them holding their interpretation of Scripture over against that of the existing Church and Tradition and the faith thus transmitted. In other words, if a given father or Council really taught and practiced SS they must be doing what the Reformers did with respect to STC.