Protestants often claim that 2 Timothy 3:16-17 are a sufficient proof of their doctrine of sola scriptura:
All Scripture is inspired by God and profitable for teaching, for reproof, for correction, and for training in righteousness, that the man of God may be complete, equipped for every good work. [emphasis added]
What then shall we make of James 1:2-4?
Count it all joy, my brethren, when you meet various trials, for you know that the testing of your faith produces steadfastness. And let steadfastness have its full effect, that you may be perfect and complete, lacking in nothing. [emphasis added]
St. James declares that steadfastness in the midst of trials has the effect of making a man “perfect and complete, lacking in nothing.” How exactly does this differ from what St. Paul says in 2 Timothy? As far as I can tell, any differences are entirely superficial, though they appear in different contexts. The results are the same.
But if this is true, then why may we not put forward a doctrine of “sola steadfastness” (sorry, my Latin is worthless, so I can’t do my new term proper justice here)? If one can claim that 2 Tim. 3:16-17 “proves” sola scriptura, then as far as I can tell we can with equal legitimacy say that James 1 proves “sola steadfastness.” Thus Scripture is reduced to a contradiction, and thus it cannot be the case that 2 Timothy teaches what the Protestants claim unless (at the very least, though there are other problems with their argument too) they are also willing to concede that steadfastness in trials results in completeness and perfection no less than the Bible. But if they concede this, then sola scriptura is demolished because a man may become perfect and complete through steadfastness in trials and not by use of the Bible (as sola scriptura argues from 2 Tim. 3:16-17).