When I was 19, I was reading a theology book by Charles Hodge. The author's book happened to be one of the larger ones on theology in the library of the college I was attending. I was trying to figure out how to answer the Catholic challenge to how the Protestant knows which books of the Bible are the right ones or not. The simple way of putting this to the Protestant has been to point out that there is no inspired table of contents. Since the Bible does not tell us which books are in the Bible, how are we to know which books are in the Bible?
The question about “which books” is a good one, but the framing of the question about there being no inspired table of contents only works for Christians who use the Bible as their criterion for truth. Another way of saying this would be, “Christians who use the Bible as their foundation for epistemology, are going to be hard pressed in answering the question, because that foundation provides no answer.”
Plenty of Protestants do use the Bible as a foundation for their epistemology, but the Bible was not always looked at this way. A book that lays this out extensively, is “Canon and Criterion in Christian Theology,” by William Abraham. One point of the book traces how the Canon became a functional epistemology, rather than living words from which we derive our daily bread. The forces which led some Christians to use it this way are well attributed in the book and are worth the read. A simpler way of talking about the Bible is that it is God’s grace to his communities to help them live out their faith and morals.
Upon leaving the library that day, I had a descent answer for “How a Protestant (or Catholic) knows” which books are to be in the Canon or not. Internal and external evidence. Internal and external evidence provides a good answer to this epistemological question. In fact, the back and forth between plenty of Catholics and Protestants on this very subject, usually misses the question altogether.
In my own correspondence with Catholics, it seems we are often we trying to get at the answer to another kind of question. It is the question of authority. Is it the Scriptures or is it the Catholic Church? At this point the Catholic rightly challenges the insufficiency of some Protestant thinking. The Protestant may only prove they are arguing in a circle. “The Bible is the authoritative document for the Church because the Bible says so.”
The Catholic however, at least plenty of writing from Catholic apologists on this subject, finds themselves in a similar circular position. Why? The Catholic answer for how we know which books are in the Bible is “Because the Catholic Church has told us so” or “because the Catholic church determined that long ago.” With a little further push, we can ask, “How do you know that the Catholic Church told you so” and “How do you know the Catholic Church determined that long ago” and “How do you know they made the right decision regarding the Canon?”
Here the Catholic may try to get out of the circle, but the obvious answer lingering over their head is “Because that is what we are told by the Catholic Church.” The intelligent Catholic will see the problem with this and may begin to discuss Jesus’ words to Peter as well as an unbroken line of bishops from the Apostles onward to solidify their position. This is of course allowed, but everyone should see that the Catholic has now moved from “authority” to arguments and evidence, which is the same position the Protestant has to make decisions from.
All of this proves that for an individual Catholic to “know” why their authority is right about Scripture, they must employ arguments and evidence which hope to show the conclusion. That is what epistemology is all about. Therefore, for Protestants and Catholics that are aware of what the question “How do you know what you know” is all about, they will have to begin engaging in arguments and evidence.
This is obviously true as witnessed in encyclopedic and academic discussions by Catholics on the subject. Even the Catholic must search the question of “Why the Church picked some books over other books?” And, because of that they will have to go look at the same sources that Protestants look at to discover a ‘good enough’ answer. By “good enough” I mean to say, “satisfactory to their conditions.” The difficulty with a historical subject like the Canon is that we will have to deal with approximate truth, not mathematical certainty.
The point here is that each person has to sort through the historical evidence about which books were adopted by the Christians as a whole, or by some smaller group of Christians in one region or another. All of this is quite tedious in some respects. There are hundreds and hundreds of pages to sort through. I have often gone back to look over the evidence and arguments from each side. One’s feeling of being ‘settled’ on the question can be unsettled at times.
The same goes for Catholics. Even if a Catholic feels “settled,” it likely has more to do with a prior commitment to the authority of the Catholic Church, than it does to arguments and evidence. That prior commitment however still needs to have arguments and evidence to support it. Therefore any Catholic’s supposed certainty on a topic, are still subject to searching the arguments and evidence they considered to have convinced them of such commitment in the first place. Thus, even a Catholic might become unsettled if pushed enough to consider more.
The ‘feeling’ of ‘being settled’ on a topic has more to do with one thinking they have covered the kind of information that could or would satisfy them. Therefore, there is no telling if one will always feel settled on such a matter because the prospect remains that they may have weighed the evidence improperly.
2 Stories – Protestant and Catholic on “being settled.”
A Protestant Christian researches the question of the Canon and thinks they have settled the issue in their own mind and heart and are glad to discuss the question with whoever may be interested. One such encounter with a well-trained Catholic unsettles them a bit. Although they knew some of the things the Catholic pointed out, such as the fact that some Church Fathers held the Apocrypha as Scripture, they did not remember there being so many.
Moreover, this Catholic seemed to be aware of the sources she was using to share her position. This situation put her at a loss because she could not share anything that the Catholic had not already read. She felt she could not get the upper hand if she wanted to. As much as she thinks her information is valid, she found the Catholic’s challenge formidable.
What does a Protestant Christian do to settle the question again? They must open their source materials and weigh the arguments and the evidence once more. Perhaps they were speaking with too much epistemic certainty in times past, and now they need to re-examine how certain their position was.
A Catholic Christian researches the question of Petrine (Peter’s) authority which begins in Matthew 16 and continues to this day in the Pope. The road of study was long, but the Catholic thinks they have settled the issue in their own mind and heart. Moreover, they are glad to discuss the question with whoever may be interested, especially with their Protestant friends (maybe they will get another Scott Hahn out of their witnessing!).
However, they happened to sit down on a plane with a well-trained Protestant who points out that the early church fathers such as Origen and Chrysostom did not hold to such a view on Petrine authority. Moreover, others such Irenaeus present only a partial case which appears more Orthodox than Catholic. Since the church fathers are often the backdrop of much Catholic Apologetics, the Catholic begins to question the kind of knowledge he had.
What does a Catholic Christian do to settle the topic in their mind again? The only thing they can really do (to get at the truth) is to go and look at the source materials again. Was the Catholic position as clearly laid out in the Church Fathers as Catholic Answers wanted them to think? If they are kind and wise, they may choose to moderate the kind of certainty they say they have on the topic in future conversations, at least with well-trained Protestants.
Perhaps Catholics and Protestants can serve each other by making sure neither group speaks with epistemic certainty on topics that are much more inductive and hence approximate. Charles Hodge’s answer was incredibly simple and (accidently or on purpose) gave the right answer to how we know what we know about the Canon or even Petrine Authority. The question is one of epistemology, and the answer is simply internal and external evidence. That must be our method. Moreover, we should answer in approximating ways on these topics. “I am fairly certain this is the case” or “I think there is strong, moderate, or weak evidence for this being the case.”
The above highlight’s the very large role of reason in figuring out these questions. Neither the Protestant or the Catholic can get around (nor should they) the use of reason in their quest for if the Canon is correct or if the Catholic Church is the true church. One does not come to accept the authority of the Catholic church, especially if they are Protestant, without arguments and evidence. One does not see a smaller Canon as the right decision, except with arguments and evidence. The available arguments and evidence on such topics must be processed through the lens of reason.
Even if one says, “I have faith in God that the Scriptures are the right one’s” or “I have faith that God chose the Catholic Church,” they still must explain how they went about thinking it was the right decision to put faith in such things in the first place. Reason is the court by which our thoughts are formed, whether we like to admit it or not.
How does Protestant Sarah know?
If a Protestant named Sarah is asked the question about how she knows if the right books are in the Canon, she has several routes before her.
1st – According to Reformed Epistemology, she can simply say, “The belief that I was raised with, namely that the Canon contains 66 books, has had no serious defeaters (reasons against it) to change my belief to something else. I have searched the question out, and I think that I am settled on the topic.” In other words, there is no good reason to give up her belief in the Canon.
I think it is important to point out that the Catholic can use this approach just as well. The Catholic can say, “I was raised with the belief that the so-called Apocrypha is actually God-breathed Scripture, and therefore the Protestant Canon is incomplete. Since I find no serious defeaters to the position, at least nothing serious enough to give up my belief, I will keep my belief.
2nd – Sarah can simply say, “The Church of the first centuries was well within their right to define the Canon in the way that they did. They had to guard from false teaching and recognize the most sacred texts for their community. What would form them and their future mattered. Therefore, I think the church of the first centuries made the right decision.”
This is not a complete answer, but what it hints at is that the nature of the canon is something defined by a community. Moreover, this is a beneficial historical route that does not get caught in circular reasoning. Some Protestant traditions don’t accept tradition (does anyone see the problem with this? 😊 ). These Protestants will typically try avoiding the church history route as a viable path. This is totally unnecessary.
The answer that Sarah gives to the question can affirm good Christians of long ago, helping to define the future of her faith. By affirming these decisions, she is not obligated to affirm any other decision of the early church or the church in centuries afterward. She thinks fallible people can come to good conclusions at least some of the time. Since she seems open minded about such matters, she likely will search out other issues in this same way.
3rd – Sarah can say in a more point-blank way, “There are good arguments and evidence for thinking that the books in the Bible are the correct ones (or the right number of them). Here she will have to point to Jewish history and a smaller Canon, the New Testament which never quotes from a text from the deuterocanonical texts, as well as the centuries that followed where she thinks that ‘on the whole,’ there is good enough reason to side with the Protestant conception of the Canon. Although, since she knows this is an inductive approach, and hence approximate, she decides to accord the ‘extra books’ a valued place in Christian history and reads them occasionally.
It is also important to point that the Catholic has the same route available to them. They can try and point to arguments and evidence.
4th – Sarah, especially if she is leaning to the more spiritual side of herself, may say, “the books of the Bible, given they had the very breath of God in them or upon them, worked through the community of God to help them come to the right conclusion. In this sense, God is the primary cause of the church concluding rightly about the books of the Bible. Of course, if pressed she will have to answer questions as to why there was not unanimity through the first few hundred years, especially in relation to the deuterocanonical texts.
The questions “How do you know which books are in the Bible?” and “How do you know the Catholic Church is the true Church (the Petrine Authority question)?” are both epistemological questions. Circular reasoning on the part of the Protestant or the Catholic will not get the job done. To get the job done, each will have to use their reasoning and search through the various arguments and evidence and weigh their conclusion approximate to the data. Perhaps Catholics and Protestants can afford each other the grace of helping each other lower their level of certainty, while also feeling comfortable as they follow Christ, whether with more or less inspired books.
 I use the word “Protestant” here because of the quick and easy understanding it conveys in contrast to Catholicism. I prefer the terms “catholic” and “orthodox” and perhaps “Anglican” or “Wesleyan” to describe my theology. Protestant does not really convey my thinking very well or the hopes I have for one day seeing Jesus’ prayers in John 17 to be realized.  Epistemology is the study of how we know what we know. The question being posed is more of a philosophical question than a theological question.  I say “no answer” to make quick sense of something. The truth is, that it provides some internal answers, but they are not complete without external evidence as well. And even then, there is not perfect completeness.  Matthew 4:4  Protestants who have used the Bible as a prooftext for all truth, will find it difficult to be consistent in answering the Catholic’s challenges. Protestants in the Wesleyan, Anglican, and to some extent Lutheran and Reformed Churches, churches which are happy to draw on Christian history and reason to form a wider angle on such topics, will not feel crunched by the question (if they know their theology).  A good book covering this approach is “Canon Revisited” by Michael Kruger. This epistemology comes especially from the Philosopher Alvin Plantinga.  Books you could consider for your own research could be some of the others already cited, as well as “Canon” by F.F. Bruce. Also, “The Canon of the New Testament” by Bruce Metzger. One can also find helpful resources on “Canon” when searching the topic on newadvent.org which is a Catholic Encyclopedia Website.  “Canon Revisited” by Michael Kruger again spends some time on this topic but in more formal ways.