That led to debate about whether the James of scripture was actually Jesus’ blood (half) brother-- which resulted in additional back-and-forth about Mary’s perpetual virginity.
The debate degenerated along typical Protestant-Catholic lines. Protestants pointed out how Mary’s perpetual virginity is extra-biblical (true) and therefore wrong (not necessarily). Catholics pointed out how Protestants don’t really follow sola scriptura (too much of a generalization but certainly not true in many cases), and that it was not even possible in principle to follow sola scriptura (definitely not true) and that Protestants also believe things that are extra-scriptural, i.e., have their own traditions (true).
There was the usual silly charge against sola scriptura, namely that you can’t possibly prove it using the Bible alone, for it would require circular reasoning. I am not going to address this in depth because so many excellent expositions exist regarding the biblical proof of sola scriptura that I have nothing of substance to add.
"Proving" sola scriptura is a two-step process, namely:
- Prove that the Bible is inerrant/inspired.
- Given (1), demonstrate that the Bible teaches its own sufficiency.
- The "hard" part of the proof, the part that is susceptible to the charge of circularity (but with care can answer it) is step 1, Biblical inerrancy.
- There is no logical conundrum in step 2, it is only a question of whether the Bible teaches that it contains sufficient and final special revelation. It either does or it doesn’t, but there is no reason a priori that it represents a violation of the rules of logic.
- Catholics also affirm Biblical inerrancy and so, for purposes of this debate, step 1 can be assumed.
In other words, if a Catholic argues against even the possibility, as a point of logic, that sola scriptura can be a self-consistent doctrine, he is actually attacking Biblical inerrancy. The argument should only center on whether it is taught in the Bible, not whether it can be taught in the Bible.
In my opinion there is misunderstanding about this doctrine on both sides. The doctrine does not state that everything that is true is also in the Bible. And it does not state that you may only believe something if it is in the Bible. It does say that the Bible provides sufficient revelation, so that (a) one should look at extra-biblical statements with skepticism and (b) one is never compelled or bound to believe something that is not in the Bible.
A lack of understanding leads to silly and trivial debates. For example, I was asked about the possibility of Jesus being married. I am paraphrasing, but the question went something like this:
"Since the Bible doesn’t say that Jesus wasn’t married, then sola scriptura means that you cannot faithfully believe that he remained a bachelor, since the Bible doesn’t explicitly state such as fact."
This shows a misunderstanding of that sola scriptura on at least two fronts. One is a lack of appreciation of the fact that sola scriptura does not preclude deduction and inference. On those grounds I think we can safely rule out the possibility of Jesus being married. However, on a more basic level, sola scriptura says nothing about Jesus’ marital state, other than this: If He were married, it is not necessary for us to know about it, and no church should demand its members affirm it as fact.
As for Mary’s perpetual virginity, either the Bible precludes it (because it teaches that James was Jesus’ true half-brother) or it has nothing to say about it, in which case it too is an unnecessary doctrine and adherence cannot be compelled. That is what sola scriptura means.
On the flip side, Protestants sometimes claim you cannot believe something unless it is in the Bible, or can be deduced or inferred in a straightforward manner (such as the Trinity). This is not only untrue, but a cognitive impossibility. If you believe something, you cannot tell yourself not to believe it. Take for example the book of Hebrews. The Bible is silent as to its author. Some prominent Protestants believe that Paul wrote it, while others, equally acclaimed, think James penned Hebrews. They can’t all be right. They might all be wrong. But unless they teach that you must affirm their position, they are not in violation of sola scriptura.