Here's reason number #986 why I keep the book Holy Scripture: The Ground and Pillar of Our Faith Volume One on my desk.
On another blog, I had a brief interaction with someone who claimed to not be Roman Catholic. He stated, "I don't need to be [Roman Catholic] to realize Sola Scriptura is fatally flawed."
I told him if sola scriptura is fatally flawed, this certainly isn't proven by Roman Catholic claims or argumentation. Like Romanists, if this non-Roman Catholic has God's voice somewhere else other than the Scriptures, he needs to prove it. Till then, I'll stick with that which is God breathed and which can thoroughly equip a believer (2 Tim. 3:16). I don't recall God mentioning Tradition or an infallible magisterium was "God-breathed and useful for teaching, rebuking, correcting and training in righteousness, so that the man of God may be thoroughly equipped for every good work."
I never did find out exactly what position this particular non-Roman Catholic held, he never told me. He did though respond to the above:
James, Ah, not so fast. The NIV has for 2 Ti 3:17, "thoroughly equipped for every good work", but many translations, like the ESV and NASB, don't have the word "thoroughly". And look at James 1:4. The NIV has "Perseverance must finish its work so that you may be mature and complete, not lacking anything." So perseverance will make you complete and lacking nothing? Scripture will do that, and so can perseverance? Obviously, you're taking 2 Ti 3:17 out of context. In fact, look at how the King James version translates James 1:4: "But let patience have her perfect work, that ye may be PERFECT and ENTIRE, wanting NOTHING." It's making an even stronger case for perseverance, much stronger than the case for the Scriptures in 2 Ti 3:16-17. So bible-only Christians are misusing 2 Ti 3:16-17.
In 2 Tim. 3:17, Paul uses the Greek participle exertismenos which is the participle form of exartizo. It means 'having been completely or fully equipped,' so, it doesn't matter which translation you use, the Greek says what the Greek says. If you can point to God's voice elsewhere other than scripture sovereignty declaring what is need to be completely or fully equipped, please do so. As to any other passage that would use similar phraseology, it needs to be noted that whatever other passage you use... they are all Scripture, and as such form and norm moral behavior. Apart from Scripture, you would have no way of knowing that "perseverance must finish its work...etc."
I was able to put forth this response because I remembered the same type of argument was put forth by Robert Sungenis:
If we were to use the concept of `sufficiency' that Protestants force into 2 Timothy 3:17, we could claim, in light of the similar language in 2 Timothy 2:21, that refraining from bad influences and behavior is all that is needed to make a man useful for every good work [Not By Scripture Alone, p.117].
...And then this argument was responded to by David King in depth in the span of two or three pages. Here's though is the relevant section that helped me in my response:
Sungenis notes that the phrase `every good work' is found in six other places in the New Testament (2 Tim. 2:21; Col. 1:10; 2 Thess. 2:17; 1 Tim. 5:10; 2 Cor. 9:8; Titus 1:16; Titus 3:1;'or Hebrews 13:21). His intent is to try to prove that Scripture itself teaches that Scripture alone is not sufficient to prepare one for every good work, since it teaches that God uses other means in addition to Scripture to accomplish that purpose. But with respect to each occurrence of `every good work' in the Pastoral Epistles (or elsewhere in Scripture for that matter), it needs to be noted that these passages are all Scripture, and as such form and norm moral behavior. Apart from Scripture, Sungenis would have no way of knowing they exist! Using 2 Timothy 2:21 to argue against the sufficiency of Scripture, he unwittingly proves the very point he seeks to undermine. Other Scriptural instances of `every good work' cited by Sungenis do not advance his claim against the sufficiency of Scripture, but rather, we find Scripture fulfilling the very purpose for which it was given as described in 2 Timothy 3:1617, namely, informing and norming for us `instruction for righteousness.., for every good work.' The question is not whether the disciplines are necessary, but what is the source of revelation which reveals them as necessary? With every quote from Scripture, Sungenis only succeeds in demonstrating that the revelatory source, by which these disciplines are normed, is none other than holy Scripture itself. [David King, Holy Scripture The Ground and Pillar of Our Faith Volume One, pp. 85-86].