Q8: In the course of your cross-examination, you seem to indicate that only justification by faith alone defines true Christianity. Is your position therefore that believers should not separate from other professing believers who hold to an open canon, the Roman Catholic canon, and/or the doctrine of “partial inerrancy”? What about if churches and entire denominations hold to these views?
A8: I think it's funny that you think holding to the Roman Canon is some sort of self-contained error. Doesn't holding to the Roman Canon lead one to believe in Purgatory? I would suggest that the problem is not so much what one would hold to as additional books in the canon as what one does with those books.
It's a serious thing to say something is Scripture. But, for example, if one holds to a canon which includes Bel and the Dragon, and reads it as a metaphor for the final triumph of Christ without any contradiction of John's Revelation, in the worst case he has taken devotional literature too far and used it to reiterate what other Scripture actually says. He's calling Bel "scripture", but he's not really changing the message of Scripture.
The problem, of course, is that no one ever does this: those who add to or take away from Scripture always do it for the sake of doctrines either in the 66 books which they want to contest or which are not in the 66 books which they must add — usually to the detriment of the Gospel. So I would say that if someone wants to hold even to an open canon, the proof of their faith is not in what books they would add but in what doctrines they would add or undo.