Not done yet. So far a very interesting synthesis of research about how different source material documents were combined to form the Bible.
People have been reading the Bible for nearly two thousand years. They haven taken it literally, figuratively, or symbolically. They have regarded it as divinely dictated, revealed, or inspired, or as a human creation. They have acquired more copies of it than any other book. It is quoted (and misquoted) more often than other books. It is translated (and mistranslated) more than the others as well. It is called a great work of literature, the first work of history. It is at the heart of Christianity and Judaism. Ministers, priests, and rabbis preach it. Scholars spend their entire lives studying and teaching it in universities and seminars. People read it, study it, admire it, disdain it, write about it, argue about it, and love it. People have lived by it and died for it. And we do not know who wrote it. (Page 1)
A doublet is a case of the same story being told twice. Even in translation it is easy to observe that biblical stories often appear with variations of detail in two different places in the Bible. There are two different stories of the creation of the world. There are two stories of the covenant between God and the patriarch Abraham, two stories of the naming of Abraham's son Isaac, two stories of Abraham's claiming to a foreign king that his wife Sarah is his sister, two stories of Isaac's son Jacob at Beth-El, two stories of God's changing Jacob's name to Israel, two stories of Moses' getting water from a rock at a place called Meribah, and more. (Page 8)
There was evidence that the Five Books of Moses had been composed by combining four different source documents into one continuous history. For working purposes, the four documents were identified by alphabetic symbols. The document that was associated with the divine name Yahweh/Jehovah was called J. The document that was identified as referring to the deity as God (in Hebrew, Elohim) was called E. The third document, by far the largest included most of the legal sections and concentrated a great deal on matters having to do with priests, and so it was called P. And the source that was found only in the book of Deuteronomy was called D. (Page 10)
Julius Wellhausen, a famous biblical researcher, simply put the two pictures together. He examined the biblical stories and laws that appear in J and E, and he argued that they reflected the way of life of the nature/fertility stage of religion. He argued that the stories and laws of Deuteronomy (D) reflected the life of the spiritual/ethical stage. And he argued that P derived from the priestly/legal stage. He traced the characteristics of each stage and period meticulously through the text of each document, examining the way in which the document reflected each of several fundamental aspects of religion: the character of the clergy, the types of sacrifices, the places of worship, and the religious holidays. He drew on both the legal and the narrative sections, through all five books of the Pentateuch, and through other historical and prophetic books of the Bible. His presentation was sensible, articulate, and extremely influential. His was a powerful construction, above all, because it did more than just divide the sources by the usual criteria (doublets, contradictions, etc.). It tied the source documents to history. It provided a believable framework in which they could have developed. Thus the Wellhausen model began to answer the question of why the different sources existed. The first real acceptance of this field of study, then, came when historical and literary analyses were first successfully merged. This model of the combination of the source documented came to be known as the Documentary Hypothesis. It has dominated the field ever since. To this day, if you want to propose a new model, you compare its merits with those of Wellhausen's model. (Page 12)