One of the defining characteristics of classical Protestantism in all its forms is sola scriptura, which in Latin means “Scripture alone” or “only Scripture.” This can sometimes be misunderstood as the Bible being absolutely the only authority Christians should look to on any matter, but while that is held by some Christians, it is not what is meant. What sola scriptura means is that Scripture is the only infallible rule of faith or authority, not that it is the only one of any kind. In other words, those who hold to sola scriptura do not have a problem with turning to philosophy, history, natural science, tradition, or even experience to help inform their beliefs on a variety of matters, but they simply do not treat these other sources of knowledge or authority as infallible.
This view contrasts with that of the Roman Catholic Church (obviously, since Luther was reacting to Rome). The official teaching of the RCC of course affirms that Scripture itself is infallible, but it also holds that Sacred Tradition, the tradition allegedly handed down from the Apostles, is also infallible. There may be a bit of variation on how Catholics may rank Tradition vs. Scripture, but it’s enough for now to state that official Catholic teaching upholds both the Bible and Sacred Tradition as infallible. A good example of how this plays out is in the doctrines of Mary. It is considered dogma, for instance, that Mary’s body was physically assumed to heaven, yet even Catholic theologians will admit that there is basically nothing in the Bible that even hints at this. What they will claim is that this is nonetheless infallibly true because tradition says so, even though no early church father even mentions this as well. Protestants are often aghast that Catholics could call such a teaching dogma when there is no written evidence of it from the Bible, from the early church fathers, and from early history about Christianity, but Catholics hold fast to what they believe was passed on in tradition.
In any case, one argument Catholics sometimes levy against the idea of sola scriptura is that the doctrine is itself not supported by sola scriptura. In other words, the Bible does not teach it, so it’s a self-defeating position. On face value, this might seem like a strange thing to argue because it sounds like they’re asking Protestants to argue in a circle, but I think we can set aside at the moment the issues of hermeneutic circles or possible non-circular ways of affirming it through the Bible. Let’s just look at this charge specifically: Where in the Bible does it teach that Scripture alone is the only infallible rule of faith?
The text Protestants often turn to is 2 Timothy 3:16-17: “All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, so that the servant of God may be thoroughly equipped for every good work” But again Catholics will ask: Where does it say Scripture alone? After all, Catholics would have no problem agreeing with that verse. Catholics often think that this is a fool-proof way of refuting sola scriptura.
To be honest, though, this argument has struck me as a bit odd. Sure, there is no verse that explicitly states that the Bible alone is God-breathed or infallible. Of course, there are no verses that explicitly say the word “Trinity” or even say that the Father, the Son, and the Holy Spirit are exclusively God. That, obviously, does not mean that it is reasonable to speculate that there is a fourth member of the Godhead, maybe God the Street Fighter, in which case the Trinity should be more like the Quadrinity or something. What the Scriptures do tell us is that the Father, the Son, and the Holy Spirit are each properly called God and yet there is only one God, from which we have formulated the essential doctrine of the Trinity.
Similarly, there is no need for Protestants to find a verse that says explicitly that the Bible alone is the only infallible rule of faith. All Protestants need to point to are verses like 2 Timothy 3:16-17 that affirm that it is the written Scriptures that are considered God-breathed (even though the NT was not yet finished at this time, it is clear that Paul himself as well as Peter considered their own writings to be authoritative). So we have one positive affirmation of the divine nature of the Bible. What affirmation do we have of anything else? Not much. One of the main verses Catholics turn to in order to support the importance of tradition is in 2 Thessalonians 2:15: “So then, brothers and sisters, stand firm and hold fast to the teachings we passed on to you, whether by word of mouth or by letter.” However, this is unconvincing; Paul is addressing them because he himself had taught them something about the man of lawlessness and his letter was to remind them of it. This does not mean that we need to surmise that there is this great big oral and infallible tradition that was quietly passed outside of the written Scriptures for centuries. All that means is that there were specific things Paul taught the Thessalonians, which they all knew, and which he was reminding them of.
Catholics also claim that they gave everyone the Bible and nobody would know the Bible is inspired unless they told them, but not only is that highly debatable, it’s a bit beside the point at the moment. The question right now is whether or not the Bible gives good reason to hold to sola scriptura. Even if one were to buy the Catholic argument here about how their great tradition provided the Scriptures for everyone, a Protestant could just thank the Catholic Church for doing so and simply hold that while they were correct on the infallibility of the Scriptures, this does not mean that tradition itself is infallible.
So here’s what we have: Taken as a whole, we do have biblical evidence that the Bible itself is divinely inspired or God-breathed. We do not see any other source of knowledge called such. We have no reason to speculate that there is another, anymore than we have a reason to speculate on the fourth person of the Godhead. It gets worse when certain teachings like many dogmas on Mary are either completely absent in the Bible or even grate against the Bible’s teachings. If we have one affirmed infallible rule of faith and another claimed rule of faith is unsupported by it, well, we have good reason to reject the latter as an infallible authority. The Catholics are arguing backwards here; Protestants need only to show that the Bible views itself as divinely inspired. If Catholics want to put something else up on the plate, it’s up to them to give the positive case for it.