The context is obviously a legal one, but I think this is a good rule of thumb to go by. Everybody wants to believe that what they believe is true. I'm not talking about theology and interpretation, but about the historicity of one's beliefs. Christians, all Christians, have many suppositions that they carry along with their beliefs. For instance, the major one being inspiration and inerrancy. The Bible doesn't claim any of these for itself in the modern sense.
True, there are statements such as Matthew 5:17-18 and 2 Timothy 3:16. However, none of these prove the Christian supposition. Paul, for instance, says that "all Scripture is inspired" and beneficial. In context, he is clearly referring to the 22 (24) books in the Old Testament, but because of different counting we have 39. So at best, Paul believed these 39 books to be inspired. He's certainly not talking about the 27 which would later compose the New Testament canon. But even with these 39 "inspired" books, Paul says that they only see things "hazily," that is, not in its full splendor. Thus, even for an "inspired" book, it is still, in some sense, insufficient.
Moreover, I will argue, that there are different sorts of "inspiration." For instance, if the Apocalypse of John is inspired, then this is a revelation from God. Still, other books such as Ephesians (if or if not we accept as genuine Pauline) would be "inspired" in a different sense. This epistle wouldn't be a revelation from God as the Apocalypse would be. This epistle can be considered to be influenced or simply approved by God. Thus, in this sense, it is "inspired."
So inspiration is a tricky and complex subject. However, if we get away from this supposition of inspiration, what parts of the Bible and of other extra-biblical literature can we verify as historical? How much of the Gospels can we say with a fair amount of certainty actually happened?
This is actually a fairly complex issue. It is complex because we are dealing with "sources" not really documents. The general scholarly consensus holds to the theory of "Q." That is to say, that Mark was the first Gospel written and that Matthew and Luke used Mark and "Q" as a source. Where Matthew and Luke have unique material not found in "Q" or in Mark, then they used sources named "M" and "L."
And in Historical Jesus studies, you have to have at least 2 independently attested events for it to have probably happened. If it appears in 3 or more, it almost certainly happened.
So for instance: An event occurring in Mark, Matthew and Luke wouldn't equal 3 sources. It would only be 1 source since Matthew and Luke copied Mark. However, if this same event occurred in John, then you do have 2 sources (Mark & John).
The methodology, in my opinion, is good. That is, events occurring in 2 or more witnesses should be given the most priority and we should probably base our beliefs on that which is most certain.
However, I do disagree with the two source theory. I don't think "Q" existed nor do I think Matthew and Luke used Mark. Of course, I am now disagreeing with about 99% of scholarship. But I think there is good evidence for the independence of Matthew and Luke from Mark. I think oral tradition, eyewitness testimony, chreias, and a few other methods explain the similarities and differences in the Gospels. There is no need for the assumption of literary dependence, that is, literary dependence that assumes Matthew and Luke used Mark. I think it is plausible they did use similar sources, but not each other.
I will get into all this at a future date, but I will, in my next entry, get into a few accounts that I think are nearly 100% certain they happened.