Sola Scriptura is a topic I have written a lot on, including my book Not by Scripture Alone: A Latter-day Saint Refutation of Sola Scriptura (an online version can be found here). There has been no meaningful response to this work by Evangelical apologists (Kathy Peterson embarrassed herself on this; see Responding to a Protestant Apologist on Sola Scriptura).
The worth of studying historical theology is that one can see that many of the “proof-texts” used for Sola Scriptura (as well as Sola Fide and other Protestant heresies) were long-refuted at the time of the Reformation and post-Reformation era. Such added to the enjoyment one had of reading Bellarmine’s Controversies. Here are some of his comments against some arguments of his time in favour of Sola Scriptura, arguments Latter-day Saints encounter by errant Protestants today, too. The following comes from Robert Bellarmine, Controversies of the Christian faith (trans. Kenneth Baker; Keep the Faith, 2016)
2 Tim 3:16-17
Bellarmine presents the arguments of those he is responding to:
But the words “for teaching, for reproof, etc.” explain the sufficiency of Scripture. For, only four things are necessary for the man of God, that is, for the Christian teacher. First, that he can teach the doctrine of the Faith. Second, that he can refute errors against the Faith. Third, that he can teach the doctrine of morals. Fourth, that he can correct those erring in the area of morals; but Scripture does all these things. For, it serves for teaching, that is, the dogmas of the Faith; for arguing, that is, to refute those erring in Faith; for instructing in justice, that is, for teaching the precepts of justice; for rebuking, that is, to teach the precepts of morals; Paul concludes from this that the man instructed in Scripture is perfect, and suitable for every good work. (p. 252)
In response to this, Bellarmine writes:
To the other place from Paul one can respond in the same way, namely, that Scripture instructs us sufficiently, and perfects the man of God, because it contains many things expressly; and what it does not contain, it tells us where to seek it. Then I say: Paul in that place does not attribute even this sufficiency to Scripture, and this is deduced for two reasons. First, from that “all Scripture”; secondly, from the phrase “is profitable.” For, when he says “all Scripture,” he is attributing praise not only to the whole body of the Scriptures, but also to the individual books, which are profitable for teaching, for reproof, etc., and nevertheless Kemnitius says that any individual sacred book is not sufficient.
But that this is not so is clear first of all from the very way of speaking. For, by the judgment of all who know Latin, what is said about all Scripture that is divinely inspired, is said about the individual books that are divinely inspired. In the second place, because, when this letter was written, the book of Revelation did not yet exist, nor the Gospel of John, and perhaps something else was still lacking from the body of the Scriptures. Therefore, he is not speaking about the whole body of the Scriptures. Thirdly, from the reasoning of the Apostle. For, from this universal principle he wanted to conclude to a particular—the Scripture of the Old Testament; because it was inspired by God, it was profitable for teaching, for reproof, etc. For, he says also: from childhood you have been acquainted with the sacred writings, (that is, the Old Testament; for, when Timothy was a child, the New Testament did not yet exist, obviously, and the adversaries admit this) which are able to instruct you for salvation through Faith in Christ Jesus. There the Apostle in a few words attributes to the Scripture of the Old Testament everything that he attributes thereafter in many words to all Scripture. And lest Timothy have doubts about that, the Apostle proves it by adding: all scripture is inspired by God, etc.
There is no obstacle in the fact that Kemnitius objects that all these helps are not found in any one book; for, this is false that they are not found. For, there is no part of Scripture shorter than the second letter of John, yet in it we see preached that Christ is the true Son of God, which is a dogma of Faith. Also, we see preached that we should love one another, which is a doctrine of morals. Moreover, we see clearly written in that they are the Antichrist who say that Christ did not come in the flesh, which pertains to refuting heretics. Finally, we see that they are reprehended who say “Hello” to heretics, which pertains to the correction of morals.
Now, that expression “it is profitable,” however it is twisted by Kemnitius, still will never mean “it is sufficient.” For whatever he proves, he does not deduce from that word that Scripture is not sufficient; nor is it deduced that Scripture is sufficient, which was what he had to prove. For, whether you say, “Scripture is profitable for this,” or “it has this use,” or “it is referred and ordered to this,” or anything else like that, you will never signify that it alone suffices. Just as also someone may say, food is useful to nourish a man, surely is saying that food was instituted for this purpose that it nourish, but he is not saying that food alone suffices. For, if the natural heat is lacking, or some organ of the body necessary for nutrition, the food will not nourish. Therefore, the Apostle does not say that Scripture alone suffices for teaching, for reproof, etc. and therefore suffices to perfect a man; but it does help and contribute to all of these things.
And although the Apostle himself does not say “it does not suffice,” nevertheless we gather that form his other statements: Like 1 Cor. 11:34, About the other things I will give directions when I come.” And 2 Thess. 2:15, Hold to the traditions which you were taught by us, either by word of mouth or by latter. And also from this place, although it is not concluded that Paul said, Scripture is not sufficient; still it is evidently gathered that he did not say, Scripture alone suffices, because he attributes these praises to every canonical work, and we know also from the admission of the adversaries that not just any canonical work suffices, because then the others would be superfluous. (pp. 253-54)
2 Thess 2:15
The third testimony is in 2 Thess. 2:15: So then, brethren, stand firm and hold to the traditions which you were taught by us, either by word of mouth or by letter. Kemnitius and Hermannus respond to this text in two ways. First they say that the Apostle handed on the same things first by word of mouth, and then by letter, and therefore that he is not talking about an unwritten tradition. But this explanation is ridiculous. In the first place, because that disjunctive particle “or” clearly indicates that those things are different which he handed on and which he wrote. In the second place, because if that were so, the letter of 1 Thess. should contain all the doctrine which the Apostle preached to them. Without doubt he had preached the whole Gospel to them, as is also gathered from chapters 1 and 2 of his first letter to them; therefore it should contain the whole Gospel. However, it does not contain even one hundredth of it, as is clear.
Secondly, they respond that the Apostle here is talking about the teaching, which he had given them orally, and which he had not written, but was written by later Evangelists. For the Apostle, according to what they say, taught absolutely nothing which is not written somewhere in the New Testament. Brentius also in his Prolegomena endorses this solution. On the contrary. For, first of all, in this very chapter the Apostle says that he preached to them about the Antichrist, and in addition to other things, taught them when he is going to come: And you know, he said, what is restraining him now. And, Do you not remember that when I was still with you I told you this? (2 Thess. 2:5-6). But this is written nowhere, that is, when the Antichrist is going to come. Wherefore St. Augustine in book 20, chapter 10 of The City of God says that they knew what the Apostle taught orally, but we cannot know it because we did not hear the Apostle; therefore not everything was written that the Apostle said. Moreover, whether what the Apostle taught was written later or not written does not make much difference for the argument that we derive from this text. For, the Apostle does not promise that he or someone else will write what he spoke to them orally, but he simply orders that they do not give less observance to what they received orally than they do to what they receive by latter. The ancient authors understood this text in this way.
Basil in chapter 29 of his treatise on the Holy Spirit said: For I hold it apostolic to abide also by the unwritten traditions. I praise you, it is said, that you remember me in all things, and keep the ordinances as I delivered them to you (1 Cor. 11:2). And, Hold fast the traditions which you have been taught whether by word of mouth, or by letter (2 Thess. 2:15). Chrysostom on this text said: Hence it is clear that they did not hand on everything by epistles, but many things also without letters. Both the former and the latter are worthy of true faith. Oecumenius and Theophylact use the same words concerning this passage, and Damascene agrees with them in book 4, chapter 7 of his work on Faith: Paul writes that the apostles handed on many things that were not written down. Therefore, brothers, stand firm and hold on to the Traditions which you were taught whether by word of mouth or by letter. (pp. 229-30)
Deut 4:2
[A]ll the contemporary heretics believe that there is no word of God except what is written; but this proposition certainly is found nowhere [in] all of Scripture. They usually cite especially Deut. 4:2: You shall not add to the word which I command you, nor take from it, but this does not help their cause because Moses does not say, to the written word, but to the word which I command you. (p. 227)
