Recently I examined an ECF quote posted by Matthew Bellisario: Cyril's Proof for God's Special Revelation Outside of Scripture. Matthew posted quotes after I presented this question to him: If Cyril believed in another infallible "voice of God", I'd be willing to see the proof. That is, demonstrate that Cyril likewise told his readers to look to "x" to see the rest of God's infallible deposit given to humankind. Matthew's first Cyril quote didn't work out very well. I can appreciate his concession to this fact when he responded, "OK James, I can go along with that interpretation on 17. What about the following post on lecture 18? I did not see such a spirited response on that one."
He posted the following from Cyril of Jerusalem:
Lecture 18 also contains some interesting text which puts the Church herself as the head which delivers "all the doctrines which ought to come to men's knowledge." Cyril here does not say the Scriptures alone either. What do you think of this text?
"Now then let me finish what still remains to be said for the Article, "In one Holy Catholic Church," on which, though one might say many things, we will speak but briefly.
23. It is called Catholic then because it extends over all the world, from one end of the earth to the other; and because it teaches universally and completely one and all the doctrines which ought to come to men's knowledge, concerning things both visible and invisible, heavenly and earthly ; and because it brings into subjection to godliness the whole race of mankind, governors and governed, learned and unlearned; and because it universally treats and heals the whole class of sins, which are committed by soul or body, and possesses in itself every form of virtue which is named, both in deeds and words, and in every kind of spiritual gifts.
The use of the quote above by Matthew is an excellent example of how many outside of the faith misunderstand sola scriptura. Sola scriptura never argues the church isn't important, or that it does not have authority to teach God's truth. Perhaps Mr. Bellisario thinks in terms of dichotomy: a Protestant has either the church or the Bible, but never both at the same time. This is far from true. I admit, there are those who may have in fact overreacted to the errors of Rome and devalue the church. I am not one of those people. I belong to a confessional Reformed church that takes the Scriptural mandate of "church" very seriously.
As to Cyril, I don't see anything in his statement that contradicts sola scriptura. Nothing in Cyril's statement implies an infallible deposit of truth standing beside the Scriptures, which is what I asked Matthew to provide.