Source criticism is the search for the original sources that form the basis of biblical text. In Old Testament studies, source criticism is generally focused on identifying sources of a single text. For example, the seventeenth-century French priest Richard Simon (1638–1712) was an early proponent of the theory that Moses could not have been the single source of the entire Pentateuch. According to Simon, parts of the Old Testament were not written by individuals at all, but by scribes recording the community's oral tradition. The French physician Jean Astruc presumed in 1753 that Moses had written the book of Genesis (the first book of the Pentateuch) using ancient documents; he attempted to identify these original sources and separate them again. He did this by identifying repetitions of certain events, such as parts of the flood story that are repeated three times, indicating the possibility of three sources. He discovered that the alternation of two different names for God occurs in Genesis and up to Exodus 3 but not in the rest of the Pentateuch, and he also found apparent anachronisms: statements seemingly from a later time than Genesis was set. This and similar evidence led Astruc to hypothesize that the sources of Genesis were originally separate materials that were later fused into a single unit that became the book of Genesis.