RhetorTheo said:
No, I'm not kidding. How does a P/R/E define what is, and is not, scripture?
There are two methods that immediately come to mind. The first is that we trust that the early church came to the correct NT canon through the soverign guidance of the Holy Spirit.
The second way is tedius and long, and although I haven't studied this in much detail, here is a short and general outline of this method:
Starting with the Gospels as uninspired texts, they are examined to see if they are legitimate, historical documents (textual criticism plays a lot into this). If they are, and Christ is shown to be the Lord, examining His words allows for the conclusion that His 12 disciples would accurately reflect Christ's words and authority on earth (John 14:26, Luke 10:16, Matthew 18:18, etc.). Since Peter authenticates Paul's writings as Scripture (2 Peter 3:14-16), Paul's writings can be (forgive the redundancy) considered Scripture (also consider that Paul saw the resurrected Christ, which made him a legitimate apostle). I personally do not know how Hebrews entered the canon, and I'm not sure why Luke would be considered Scripture beyond the fact that he interviewed those who knew Christ and the apostles personally, but hopefully you get the gist of how some Protestants take to task the issue of the canon. If you're looking for contemporary efforts using this method, I recommend consulting Miller:
http://www.christian-thinktank.com/canonout.html
Scripture was added to with the NT, why can't it be added to again?
I have not studied this in depth either, but what I've read indicates that times of new revelation are always accompained by miracles to authenticate that revelation. I suppose new material could be added to the canon, but until miracles on the level of those described both in the Old and New Testaments (both in power and undeniablility), proposed additions should be ignored.
~Matt
PS
Sorry, but I don't have time to spell check this and proof-read. If something isn't clear, please indicate it and I'll respond as soon as possible.