Those who engage with Roman Catholicism and Eastern Orthodoxy very quickly become aware that Sola Scriptura is probably the most common vector of attack for those who would critique Protestant Christianity. Often, the discussion remains very abstract, with the Imperialist neglecting to be specific about what exactly the Protestant needs to accept, in addition to the Bible, in order to be a Christian. Rather, the main thrust of the argument is aimed at convincing the Protestant that the Bible is not enough, and then, it is apparently assumed that they will hand their conscience over to the Catholic or Orthodox Church, once that proposition is accepted.

Usually, this is seen as an easy undertaking. Certain brands of Sola Scriptura definitely are self-refuting, or indefensible, and therefore, easily torn down. Consequently, many conversion stories to Imperialist denominations begin with the convert losing faith in "Sola Scriptura", whatever that may have meant to them.

So, why should someone be "Sola Scriptura"? That is, why should the Bible be one's only infallible source for binding doctrine?

Framing the Question

The debate around Sola Scriptura is often framed in an unhelpful way to the Protestant. They are usually put on the defensive, being asked to defend a doctrine, when really, they do not need to do much defending at all. If they are speaking to a Roman Catholic, or Eastern Orthodox Christian, then they are in agreement that the Bible (at least the 66 books that most Christians can agree on) is the collection of documents most likely to have been written by the chosen Prophets and Apostles of God.

So, if the Imperialist is insisting that one should "deny Sola Scriptura", what they are really doing is proposing a corpus of documents that the Protestant should accept, in addition to what the Prophets and Apostles most likely wrote, as being dogmatically binding. As such, the onus is on the Imperialist to convince the Protestant to accept whatever extra documents they are attempting to bind to them. Often, this issue is viewed in a wholesale way - one either accepts everything that the modern iterations of these denominations accept, or they must cling to "Sola Scriptura". But, this is moving too quickly. First, the Protestant needs to examine the actual content of the corpus of texts which is being pushed onto them.

When they do examine the corpus of texts proposed by the Imperialist denominations, they will find that many texts within that corpus, constituting at least a large section of it, fail at least one of three criteria:

1. Inconsistent with itself - The text contradicts another text or texts in the corpus. For example, the Popes of the Middle Ages regularly and violently contradicted what the modern Popes write, on a whole host of doctrinal and moral questions
2. Inconsistent with good history - The text contradicts what can be historically determined to be true with a high degree of certainty. For example, the Second Council of Nicaea's (787 AD) claim that the early Christians venerated icons, and that all Christians must do so, is historically a non-starter. Vatican 1's (1870 AD) claims about the Papacy are historical fiction. The stories believed (and dogmatized) by both the Catholics and Orthodox about Mary's maidenhead remaining intact when she gave birth, or being bodily assumed to Heaven, both come from forged, apocryphal texts, written long after the New Testament. Pretending that these types of things are what the Apostle Paul meant in 2 Thessalonians 2:14-15 is twisting both Scripture and history
3. Inconsistent with the Bible - The text contradicts what has already been accepted to be the writings of the Prophets and Apostles. For example, the early Christological Councils contradict the Bible's teaching that God just is the Father

It is up to the Imperialist to make the sale for their library of extra texts, ideally, one text at a time. But, those texts, when examined, fail the above criteria. So, if rejecting them makes one "Sola Scriptura", then that is fine. A Protestant can be content only accepting as authoritative those writings which most likely came from the Apostles and Prophets. The texts composing the Bible are far more reliable, and likely to be what God actually wanted taught, than the library of late, contested, convoluted, self-contradictory material produced by theologians declaring themselves and their acquaintances "infallible" in the Imperialist traditions.

Conclusion

The entire framing of the debate around Sola Scriptura is often set up in such a way as to put a Protestant on the defensive. But, defending belief in the Bible is actually not usually an intra-Christian debate. Instead, this debate should be framed as follows: it is the job of the one wanting to bind additional content to the Scripture to justify why one should accept that particular text. And, this examination process should take a reasonable amount of time, moving through each text one at a time. Christians should be wary of anyone attempting to coax someone else into accepting hundreds, or thousands of pages of texts that they themselves have probably never read, while saying that without doing so, they are not "real Christians", or members of the "true Church", or of the "Apostolic faith", etc.