Protestants believe the Scripture is sufficient in all matters concerning faith, morals, and doctrine. Yet, Catholics and Eastern Orthodox put the Scripture on par with the infallible pronouncements of Popes and Ecumenical Councils (even though this is an idea found nowhere in the writings of early Christians.)
In De Synodis, Athanasius wrote that the Scripture “is sufficient above all things.” What’s the context? Let’s read chapter six:
But the Councils which they are now setting in motion, what colourable pretext have they? If any new heresy has risen since the Arian, let them tell us the positions which it has devised, and who are its inventors? And in their own formula, let them anathematize the heresies antecedent to this Council of theirs [endorsed in previous Arian councils]…Vainly then do they run about with the pretext that they have demanded Councils for the faith’s sake; for divine Scripture is sufficient above all things; but if a Council be needed on the point, there are the proceedings of the Fathers, for the Nicene Bishops did not neglect this matter, but stated the doctrine so exactly, that persons reading their words honestly, cannot but be reminded by them of the religion towards Christ announced in divine Scripture.
The Council of Nicea is held up, not because it inherently has authority, but because it accurately represents the ideas found in the authoritative Scripture. Throughout the rest of the book, we can see how the sufficiency of Scripture simply oozes from the pages of creeds that Athanasius copiously records for us.
One Catholic Synod of Bishops stated:
What faith was handed down? A mysterious oral tradition that gives us extra-biblical insights? Not if we go by what the councils of Bishops kept saying.
One synod stated:
Holding then this faith, and holding it in the presence of God and Christ, from beginning to end, we anathematize every heretical heterodoxy. And if any teaches, beside the sound and right faith of the Scriptures, that time, or season, or age , either is or has been before the generation of the Son, be he anathema. Or if any one says, that the Son is a creature as one of the creatures, or an offspring as one of the offsprings, or a work as one of the works, and not the aforesaid articles one after another, as the divine Scriptures have delivered, or if he teaches or preaches beside what we received, be he anathema. For all that has been delivered in the divine Scriptures, whether by Prophets or Apostles, do we truly and reverentially both believe and follow (Chap 23).
For neither is safe to say that the Son is from nothing, (since this is no where spoken of Him in divinely inspired Scripture,) nor again of any other subsistence before existing beside the Father, but from God alone do we define Him genuinely to be generated. For the divine Word teaches that the Ingenerate and Unbegun, the Father of Christ, is One…Nor may we, adopting the hazardous position, ‘There was once when He was not,’ from unscriptural sources, [i.e. Arian tradition and councils] imagine any interval of time before Him, but only the God who has generated Him apart from time; for through Him both times and ages came to be…For it is irreligious and alien to the ecclesiastical faith, to compare the Creator with handiworkscreated by Him, and to think that He has the same manner of origination with the rest. For divine Scripture teaches us really and truly that the Only-begotten Son was generated sole and solely. (Chap 26).
In the above, we see an example of the regulative principle at work. One doctrine (that Christ is “from nothing,” i.e. self-created) is wrong specifically because the Scripture does not weigh in on the issue. Hence, the principle at work is that unless the Scripture teaches something, it is not safe to believe it.
We find a similar idea talked about in yet another synod:
But since many persons are disturbed by questions concerning what is called in Latin ‘Substantia,’ but in Greek ‘Usia,’ that is, to make it understood more exactly, as to ‘Coessential,’ or what is called, ‘Like-in-Essence,’ there ought to be no mention of any of these at all, nor exposition of them in the Church, for this reason and for this consideration, that in divine Scripture nothing is written about them, and that they are above men’s knowledge and above men’s understanding (Chap 27).
And yet another:
But the name of ‘Essence,’ which was set down by the Fathers in simplicity, and, being unknown by the people, caused offense, because the Scriptures contain it not, it has seemed good to abolish, and for the future to make no mention of it at all; since the divine Scriptures have made no mention of the Essence of Father and Son (Chap 30).
The absence of there being an authority outside of the Scripture and clear reason is pretty obvious to anyone reading these statements.
Athanasius ends De Synodis saying:
What then I have learned myself, and have heard men of judgment say, I have written in few words; but do you, remaining on the foundation of the Apostles, and holding fast the traditions of the Fathers, pray that now at length all strife and rivalry may cease, and the futile questions of the heretics may be condemned (Chap 54).
In light of everything we just read, obviously the foundation of the Apostles is what we see in the Scriptures. The traditions of the Fathers, in light of this, are the correct interpretations of the Scriptures. Hence, Scripture is sufficient above all things. Tradition informs us as to how to adequately interpret Scriptures. However, we see no indication that Christians are bound to believe in doctrines and customs that have no bearing whatsoever in the Scriptures. And if this is the case, why does the Catholic and Eastern Orthodox church spend so much time saying that the consciences of Christians are bound to authorities outside the Scripture?
Athanasius would view such ideas as repugnant.