(Those who read the earlier version of Article IIIb may have expected this to be article IIIc. I decided to make it IVa simply because it is a different topic from the topic of infallibility in article IIIa and IIIb).
Of course a topic like this will invoke strong feelings. Whether Catholic or Protestant, those who practice their faith out of devotion (as opposed to a "meh, whatever" attitude of indifference) belong because they believe their teachings to be true. Of course, Catholicism and Protestantism cannot both be true.
If Protestantism is true, then it means that Catholicism added to the teachings of the Christian faith. However, if Catholicism is true, then it means that Protestantism subtracted from the teachings of the Christian faith.
I would ask the reader to remember I am not writing this as an "in your face" attack on non-Catholic Christians. Rather, I seek to demonstrate why Catholics do not recognize the concept of sola scriptura as part of the teaching of Christ.
Of course the entire subject of the disputes between Catholics and Protestants are too large to deal with in one article — or even a series of articles. The focus of this article is to lay down some pitfalls to avoid. We need to avoid the use of logical fallacies and we need to realize what is under dispute. I have certainly seen internet debates where Catholic and Protestant spoke past each other because they did not realize they used the same terms in different ways leading to each side accusing the other of being obstinate.
Argument from Ignorance is a Fallacy
One thing essential to remember is that the argument that "[X] is not mentioned in the Bible, Therefore it was added later," is an argument from ignorance. The argument from ignorance basically makes an assumption that because a thing was not said it means it is not true. Alternately, some have used it to say that since there is no argument against the view it must be true.
Neither view is correct. No logical conclusion can be drawn from nothing (no knowledge). Rather we need to see what sort of evidence exists for a belief. Now in the court of law, the defendant is assumed innocent until proven guilty. This means that the burden of proof is on one side, while the other side merely has to show why the prosecution cannot prove his case.
However, in discussions where the truth is being sought, both sides need to present their justifications, and we cannot accept the assumption that because one side has failed to present their case that the other side must automatically be true.
The fact that Scripture does not say a thing neither proves a thing nor disproves a thing. One must recognize that there can be other reasons for not speaking on a topic. For example, Paul speaking on circumcision in his epistles may find the topic of primacy irrelevant to the point he wishes to make.
This is important to remember because often debates over religious beliefs boil down to claiming "your side isn't mentioned in [X]. Therefore it is false." Because of this, we must recognize that accepting or denying a belief cannot be based on this sort of reasoning.
Assumptions and Sola Scriptura
This leads us into the next issue of concern, and that is the issue of assumptions and interpretations. What one holds to be true may in fact be true whether or not the individual can explain himself in a logical way or not. However, if one wants to convince another, there needs to be some sort of acceptance of the premise between two parties. If both parties do not accept something, then it is this issue which needs to be established before continuing. This is why Christians of different denominations do not begin their disputes with the question of whether God exists. Since both believe this to be true, they do not need to start here. On the other hand, a Christian and an atheist debating would need to be starting somewhere closer to the question of "does God exist?" (The precise spot would depend on what sort of beliefs the atheist had about the idea of what we can know, whether we can know truth and so on).
Failure to start at the point of difference will result in nothing more than a waste of time, as both sides talk past each other.
In terms of Church authority and Sola Scriptura, the difference is not over whether Catholics believe the Bible to be inspired. We do believe this to be true. The key area of difference is over the authority to interpret Scripture. If a Protestant says "Catholicism cannot be true, for the Catholic Church teaches [X] and the Bible clearly forbids [X]," the Catholic will rightly want to know on what authority the Protestant can interpret Scripture in a binding fashion on this subject. Likewise, the Protestant who hears that the Church has defined something infallibly will generally reject it because they do not believe the Pope has this authority.
Thus, the true issue between Catholic and Protestant is Who has the authority to interpret what is and is not authentically Christian.
Anyone who has been paying attention to this series so far will realize I have done my best to demonstrate the basis on which the Catholic believes in the teaching authority of the Church, though any failure is due to my own lack of ability and not that of the Church. The non-Catholic may not believe in the Catholic authority to interpret Scripture in a binding manner, but they cannot deny we do accept the authority of Scripture in holding this view.
Now, we need to look at Sola Scriptura and the basis for holding it, and why a Catholic does not accept the premise. In doing so, I hope to clear up some misconceptions on what Catholics do believe. Thus I will look at the claims of sola scriptura and do my best to find a representative view of what it means in light of the differences between some denominations on the subject.