The documentary hypothesis (DH) is one of three models used to explain the origins and composition of the first five books of the Bible, called collectively the Torah or Pentateuch, the other two being the supplementary hypothesis and the fragmentary hypothesis. All three agree that the Torah is not a unified work from a single author (traditionally Moses) but is made up of sources combined over many centuries by many hands. They differ on the nature of these sources and how they were combined. According to the documentary hypothesis there were four sources, each originally a separate and independent book (a "document"), joined together at various points in time by a series of editors ("redactors"). Fragmentary hypotheses see the Torah as a collection of small fragments, and supplementary hypotheses as a single core document supplemented by fragments taken from many sources.
A version of the documentary hypothesis, frequently identified with the German scholar Julius Wellhausen, was almost universally accepted for most of the 20th century, but the consensus has now collapsed. As a result, there has been a revival of interest in fragmentary and supplementary approaches, frequently in combination with each other and with a documentary model, making it difficult to classify contemporary theories as strictly one or another. Modern scholars increasingly see the completed Torah as a product of the time of the Achaemenid Empire (probably 450-350 BCE), although some would place its production in the Hellenistic period (333-164 BCE) or even the Hasmonean dynasty (140–37 BCE). Of its constituent sources, Deuteronomy is generally dated between the 7th and 5th centuries; there is much discussion of the unity, extent, nature, and date of the Priestly material. Deuteronomy continues to be seen as having had a history separate from the first four books, and there is a growing recognition that Genesis developed apart from the Exodus stories until joined to it by the Priestly writer.
The Torah (or Pentateuch) is the collective name for the first five books of the Bible: Genesis, Exodus, Leviticus, Numbers, and Deuteronomy. According to tradition they were dictated by God to Moses, but when modern critical scholarship began to be applied to the Bible it was discovered that the Pentateuch was not the unified text one would expect from a single author. As a result, the Mosaic authorship of the Torah had been largely rejected by leading scholars by the 17th century, and the modern consensus is that it is the product of a long evolutionary process.