Source criticism, in biblical criticism, refers to the attempt to establish the sources used by the authors and redactors of a biblical text. It originated in the 18th century with the work of Jean Astruc, who adapted the methods already developed for investigating the texts of classical antiquity (in particular, Homer's Iliad) to his own investigation into the sources of the Book of Genesis. It was subsequently considerably developed by German scholars in what was known as "the higher criticism", a term no longer in widespread use. The ultimate aim of these scholars was to reconstruct the history of the biblical text and also the religious history of ancient Israel.
In general, the closer a source is to the event which it purports to describe, the more one can trust it to give an accurate description of what really happened. In the Bible where a variety of earlier sources have been quoted, the historian seeks to identify and date those sources used by biblical writers as the first step in evaluating their historical reliability.
In other cases, Bible scholars use the way a text is written (changes in style, vocabulary, repetitions, and the like) to determine what sources may have been used by a biblical author. With some reasonable guesswork it is possible to deduce sources not identified as such (e.g., genealogies). Some inter-biblical sources can be determined by virtue of the fact that the source is still extant, for example, where the Books of Chronicles quotes or retells the accounts of the books of Samuel and Kings.
Source criticism has been applied to several parts of the Tanakh (the Hebrew Bible or Old Testament).
The documentary hypothesis considers the sources for the Pentateuch (the first five books of the Bible), claiming that it derives from four separate sources: the Yahwist, Elohist, Deuteronomist, and Priestly:
For example, of the two creation stories at the start of Genesis, the first is ascribed to P, while the second (the creation of Adam and Eve in chapter 2) is ascribed to J.
The writers of the Tanakh sometimes mention sources they use. These include Acts of Solomon (1 Kings 11:41), Chronicles of the Kings of Judah (1 Kings 14:29 and in a number of other places), Chronicles of the Kings of Israel (1 Kings 14:19 and in a number of other places), the Book of Jashar (Josh 10:12-14, 2 Sam 1:18-27, and possibly to be restored via textual criticism to 1 Kings 8:12), and Book of the Wars of the Lord (Num 21:14).
A more complicated and speculative form of source criticism results from critical evaluation of style, vocabulary, reduplication, and discrepancies. An example of this kind of source criticism is found in the book of Ezra-Nehemiah (typically treated by biblical scholars as one book) where scholars identify four types of source material: letters to and from Persian officials, lists of things, the Ezra memoir (where Ezra speaks in first person), and the Nehemiah memoir (where Nehemiah speaks in first person). It is thus deduced that the writer of Ezra-Nehemiah had access to these four kinds of source material in putting together his book.
Source criticism also leads many scholars towards redaction of the book of Isaiah from original multiple authorship.
Source criticism is the search for the original sources which lie behind a given biblical text. It can be traced back to the 17th-century French priest Richard Simon, and its most influential product is Julius Wellhausen's Prolegomena zur Geschichte Israels (1878), whose "insight and clarity of expression have left their mark indelibly on modern biblical studies". An example of source criticism is the study of the Synoptic problem. Critics noticed that the three Synoptic Gospels, Matthew, Mark and Luke, were very similar, indeed, at times identical. The dominant theory to account for the duplication is called the two-source hypothesis. This suggests that Mark was the first gospel to be written, and that it was probably based on a combination of early oral and written material. Matthew and Luke were written at a later time, and relied primarily on two different sources: Mark and a written collection of Jesus's sayings, which has been given the name Q by scholars. This latter document has now been lost, but at least some of its material can be deduced indirectly, namely through the material that is common in Matthew and Luke but absent in Mark. In addition to Mark and Q, the writers of Matthew and Luke made some use of additional sources, which would account for the material that is unique to each of them.
There is general consensus among New Testament scholars that the Mark used a variety of sources, most of them written, and that the authors of Matthew and Luke were dependent on some version of Mark plus a lost collection of "sayings" called the Q Document. There is less of a consensus that the writers of the Gospel of John may have used a hypothetical Signs Gospel.