A: The general idea of the "Documentary Hypothesis," as it is called, is that the Torah (ie, the first five books of the Bible, also called the Pentateuch) as we have it today is the result of editing together documents from three or more different sources. The idea began when a French Physician named Jean Astruc noticed sometime in the middle of the 18^th century that Genesis 1 referred to God as "Elohim" and Genesis 2 -- which seems to tell an alternative story of creation – used the name "YHWH" (commonly rendered Jehovah) . Subsequent scholars took this idea and ran with it, scouring the entire Pentateuch for evidence of underlying sources, based on alleged variations in point of view, vocabulary and style. The source of Genesis 1 is designated "E" for "Elohim." The source of chapter 2 is called "J" for Jehovah. Later theorists proposed even more alleged sources, such as "P" for Priestly Code , "D" for Deuteronomy., and "H" for Holiness.

Using these criteria the documentarians attempted to explain the various "doublets" or (alleged) multiple accounts of various Biblical episodes – the J version and the E version. The original documentarians viewed these sources as pre-Mosaic documents which Moses must have used to compile the books known by his name. In 1805, Wilhelm M. L. De Wette asserted that none of the Pentateuch dated back before the time of David, ie., about 1000 BC. Furthermore, he claimed the book of Deuteronomy was an entirely new fabrication created in the days of King Josiah (621 BC), expressly to be "found" and justify the king's reforms!

Originally it was assumed that E was the oldest document, and that some later "redactor" added the later material called "J" In 1869, however, a Dutch scholar named Abraham Kuenen argued that J must predate E, because J is so full of "primitive" anthropomorphisms. When Julius Wellhausen wrote his definitive book on this subject in 1878, he had the main sources in the order JEPD, reflecting an evolutionary view of the development of the Israelite religion from more primitive to more complex.

There are many problems with the documentary hypothesis. Name differences are no longer considered a valid criterion for source division. The Septuagint does not correspond to the Masoretic Text with respect to divine names in no less than 180 instances, so there is no assurance which names originally went with which passages anyway. For another thing, different names are sometimes used together in the same passage, making it very difficult to assign it to one source or the other without assuming a later "redactor" to edit them together, and that would be circular reasoning.

It is perfectly reasonable for one author to use different names for the same person, anyway. For example, a newspaper article might refer to "The president" in one paragraph and say "Mr. Clinton" in another, but no one assumes the article must have been written by two people on that basis alone! Besides, many ancient cultures, including the Babylonians, Egyptians and Greeks, had multiple names and titles for the same gods.

The documentary hypothesis is also called upon to explain alleged double-accounts and discrepancies, but the use of repetition and duplication is common on ancient Semitic literature. Most "discrepancies" disappear with careful exegesis.

You can find a very fine discussion of the issues in "A Survey of Old Testament Introduction" by Gleason Archer, which has been published by Moody Press in Chicago.