A few responses all crammed together, if you will permit me...
1. When Paul was referring Timothy to 'all Scripture' in 2 Timothy 3:16, the reference there had to be what we call the Old Testament and what they referred to as the Law and the Prophets (this was the general term, but did include the books of poetry, such as Psalms). It has nothing to do with the Gospels, Acts, the Epistles, or Revelation, which are the New Testament.
What is interesting is that in 2 Peter 3:16, Peter refers to Paul's writings as Scripture! However, when Paul was writing to Timothy, his reference would have been to the Law and the Prophets.
2. The basic purpose of the Scriptures was to describe man's relationship to God and God's provision for those who believed on Him. It deals with true history and true science, but it is neither a history nor a science text. However, where it deals with history or science, it is accurate. It might be said that the Bible is a history and science guide, giving the parameters within which the truth can be found. My husband and I have found, in our combined areas of research, that this is exactly right -- the Bible knows what it is talking about in whatever area it touches.
3. Assyrian, it is common among all the Christian churches I have attended (several different denominations) to consider the Bible inerrant in the original mss/tablets. If you consider what the Bible is, what comprises it, that is not hard to understand.
Evidence is mounting that Genesis itself is a series of eyewitness tablets, signed off by each of the respective authors. These would have been collated and edited by Moses (we can see some editorial comments in them) and thus considered one of his books, along with the rest Pentateuch. The four other books are history and law. Then you have the other books of history, written by the scribes of the times lived. Following that is Job, which is the earliest completed book of the Bible, describing the time immediately following Peleg.
The histories in these books are either true or they are not. They do not leave room for 'part myth, part truth.' They are presented as straightforward history and must be accepted or rejected on their own terms.
Following them are the books of Poetry: Psalms, Proverbs, Ecclesiates, Song of Songs (Song of Solomon). It is these books you might want to agree or disagree with in part. The Israelites, however, considered them to be Holy Scripture, having stood the test of time and concordance with the rest of Scripture.
Then the OT has the books of the Prophets. A lot of history is repeated here and/or referred to. Again, the history itself is either accurate or it is not. It was considered by the people of the time and those that followed to be accurate. The prophecies themselves which are contained in these books have shown themselves to be startlingly accurate.
Now, are there problems with our modern versions? Yes, some. For instance, the Masoretic text, which is the basis for our Old Testaments in English and most other modern languages, systematically drops a cipher for 100 from the genealogies in Genesis 5 and 11. When these years are added in, the earth's age is extended by about 2000 years and there is no longer any problem with coordination with Egyptian chronology. The original numbers can be found in the Alexandrian Septuagint, which was translated 250-300 years before Christ by Hebrew scholars from paleo-Hebrew to classical Greek. So we do have this check for a number of things, and we can see where the translators of the Masoretic seemed to have something going on which has caused some arguments later.
We have found, probably originating in the Middle Ages when all was being done by hand, a few transposed numbers and such, and the spelling of some names is altered somewhat. That is most of the changes, actually.
Aside from that, there are three parts of the New Testament which are not found in the earliest mss. The first is the ending of Mark. The earliest mss we can find end Mark with 16:8. The addition later is one which has caused enormous confusion, for it is the only place where it is written that baptism is necessary for salvation and it is also the place where it was written that poison could be drunk and snakes handled without harm. This is entirely different from everything in all the rest of the New Testament.
The second passage which is not in the earliest mss is actually a very famous one. It is when the woman caught in adultery is brought to Jesus. It may very well have happened, but, as I said, the earliest mss simply do not have this incident (John 7:53-8:11).
The last known alteration in the NT appeared to have happened, again, in the Middle Ages, when a marginal note by someone was inserted into the text. This can be found in 1 John 5:7-8 and is usually given in study Bible text notes rather than in the text itself.
But in the long run, the Bible is still totally dependable. The history is valid, the science is valid, the prophecies are valid, and the message God has given us about our relationship with Him and what He has done for us in Christ Jesus is unchanged through time. Those who doubt the message or the validity have been given the science remarks and the history to help validate the authenticity of this Book.
And that is why the science and history are so vehemently attacked by some. If you can destroy credibility, then all man had to depend upon is himself. For some, that is exactly what they want.
For me, I have found God is faithful and I can depend on Him entirely.
4. Mallon, if the Scriptures were written as filtered through man's understanding, then we would not have passages such as "Concerning this salvation, the prophets, who spoke of the grace that was to come to you, searched intently and with the greatest care, trying to find out the time and circumstances to which the Spirit of Christ in them was pointing when he predicted the sufferings of Christ and the glories that would follow." 1 Peter 1:10-11.
Rather, the histories were given by those who lived them. The prophecies were from God and they clearly did not always understand what they were writing, but they were faithful to put down what they had been shown.