Well!
The post below on possible sources in the Pentateuch really triggered an avalanche of comments regarding the subject of inerrancy.
Rather than do a reader roundup on this, lemme address the subject in a more general way and see if that helps folks out.
First, the teaching of the Church is and always has been that the Scriptures are free of error.
This has to be understood with some nuance, however, as there are things in Scripture that could be taken in a sense that is erroneous. That does not make them errors. It means that the understanding being ascribed to them is erroneous.
For example, when Jesus teaches a parable and says that there was a man who rented our a vineyard and, when it was time to collect his share of the crop, he sent them servants who got beaten, stoned, and killed, and who later sent his son, on whom they fixed murderous designs–it would be erroneous to assume that there was such a man who did all these things. Jesus is asserting something in the parable, but what he is asserting is the deeper spiritual truth that the parable is meant to teach. He is not asserting the literal existence of such a man.
Thus we need to attend to what Vatican II said about the matter in Dei Verbum 11:
Therefore, since everything asserted by the inspired authors or sacred writers must be held to be asserted by the Holy Spirit, it follows that the books of Scripture must be acknowledged as teaching solidly, faithfully and without error that truth which God wanted put into sacred writings for the sake of salvation [SOURCE].
Some have tried to argue that the clause "for the sake of our salvation" narrows the scope of inerrancy to just truths connected in a more or less direct manner with salvation. This won’t work, however, because the passage affirms that "everything asserted by the inspired authors
or sacred writers must be held to be asserted by the Holy Spirit." The only way this could be maintained while simultaneously maintaining that biblical inerrancy is restricted to soteriological truths would be if the only things the sacred authors assert are soteriological truths.
That hypothesis would clearly be false.
It is clear that Scripture does assert things, including matters of history, that are not soteriological. For example, Scripture clearly asserts that Peter was the brother of Andrew in some accepted first century meaning of the word "brother." It teaches the same for James and John, the sons of Zebedee. These matters are historical (at least from our perspective), not soteriological.
Consequently, Scripture contains assertions of a non-soteriological nature, including assertions about history, and such assertions are therefore assertions of the Holy Spirit and therefore without error.
The “for the sake of our salvation” clause thus refers to the purpose for which God put his truth into Scripture, not to a restriction on the scope of God’s truth.
The tricky part is figuring out what is an assertion and what isn’t. Scripture is a complex and rich text that uses many different means of conveying God’s truth. Since some of these involve ancient modes of writing and speech that are not used in 21st century English literature, it isn’t always clear to us what precisely is being asserted. Indeed, Scripture acknowledges that it isn’t always clear, as when St. Peter notes that St. Paul’s writings contain many things that are hard to understand (2 Pet. 3:16).
This difficulty in figuring out what is being asserted by the sacred author has thus been with us since the beginning. It is a principal cause of theological disagreements among Christians, and it is a sign that God wishes us to (a) use the intellects he gave us to try to figure out what he was saying to us and (b) since "no prophecy of Scripture is a matter of private interpretation" (2 Pet. 1:20) to also exercise the theological virtue of faith in relation to the Church, "the pillar and ground of truth" (1 Tim. 3:15) to help us when our own intellects fail.
Above I used the example of a parable of Jesus to show the difference between what the sacred author is asserting and how this could be misunderstood by misinterpreting the sense in which the particulars of the passage are to be taken (i.e., as a literal story of an actual historical event). I picked this because it is an obvious example.
Most of the time, the difficulty is not so obvious. The historical books of the Old and New Testament contain real history, but it is not history written the way we would write history today. It obeys the rules of ancient historical writing, which are significantly different (e.g., you don’t have to footnote everything you claim).
Because we do not today have a full understanding of the rules by which the ancients wrote history (and the rules varied from culture to culture and from time to time), it can be difficult figuring out what is being asserted in the proper sense and what is not being so asserted.
When we encounter something that is not being asserted, we cannot charge the sacred author with error because only assertions can be erroneous. If I’m not asserting that something is true then I am not making a claim that can be in error. The most that could be said is that what I said would be erroneous if taken as an assertion of fact.
Thus if I talk about the sun rising in the morning, and someone fails to note that I am using phenomenological language (the language of appearances), he might say that what I said was false, but he would be wrong. I was not asserting that the sun literally rises in relation to a stationary earth. That is not the sense in which I meant my words to be understood, and so that is not what I was asserting. I would be wrong if I had meant that, but I didn’t mean that. Therefore, my assertion was not false.
When we approach Scripture, we must be sensitive to the fact that there are many things in it that may strike us as being assertions that, to the ancient audience, would not have been so understood. If we run across something that seems false or seems to contradict some other passage, we know that what Scripture says is not wrong. We simply have not correctly identified what is being asserted in one or both passages.
UPDATE: HERE, TOO.