Who put all of the books of the Bible together in one book, and how do we know that they were right?
The logic of the answer to this question is fairly simple, but the evidence is a bit involved. In order to give you a sufficient answer, I suggest you read the chapter in my book "Reasons for Belief" about the reliability of the Bible. Also, there is an outline and power point available at the web site titled "How We Got the Bible" and an article at the web site titled "A Remarkable Collection."
But let me give you the short version. There is obviously no single person who put the Bible together. Some people have suggested that Constantine put the New Testament together. Anyone making this claim is either very ignorant of the evidence or is willfully deceiving.
In the case of the New Testament, the books which eventually made up the accepted 27 in our Greek Bible were selected over the course of roughly one hundred years by consensus of the church "fathers." The four gospels and Paul’s letters were collected and circulating by about AD 90 or perhaps ten or twenty years earlier. By the early second century, those books which were recognized by the church as a whole as having apostolic authority began to be considered a "New Testament." By about AD 150 there was near consensus of all the churches on the content of the inspired books. There was still some debate about a few books at this date, such as 2 Peter, 3 John, Hebrews and Revelation. By about AD 180 the current New Testament canon was virtually accepted as we now have it. We know this both from lists mentioned by writers such as Irenaeus, and from the books which were quoted by early church leaders as having authority.
So, as you see, there was no single person responsible for deciding which books had apostolic authority. If you read the NT books and compare them to books which were NOT accepted in the New Testament, such as the Didache, the Letter of Clement of Rome and the Epistle of Barnabus, you will see immediately a qualitative difference in quality of the New Testament books. In the end, Christians accept on faith that God–directly or indirectly–chose and caused which books ended up in the New Testament. My belief in the reliability and authority of the currently accepted New Testament is based both on the evidence and on faith that God is in control of such things. Bottom line, we know that "they were right" by faith. We cannot get away from the role of faith, despite the evidence for the quality of the NT books.
A similar case can be made for the Old Testament, except that we do not have nearly as much data about how the books were selected. I will let you do the research at my web site or get a copy of Reasons for Belief to discover the details.
John Oakes, PhD