Book of Deuteronomy have given various answers to the problem. The Deuteronomistic history theory is currently the most popular (Deuteronomy was originally just the law code and covenant, written to cement the religious reforms of Josiah, and later expanded to stand as the introduction to the full history); but there is an older theory which sees Deuteronomy as belonging to Numbers, and Joshua as a sort of supplement to it. This idea still has supporters, but the mainstream understanding is that Deuteronomy, after becoming the introduction to the history, was later detached from it and included with Genesis-Exodus-Leviticus-Numbers because it already had Moses
Old Testament account for the many different Old Testaments which exist today. Timothy H. Lim, a professor of Hebrew Bible and Second Temple Judaism at the University of Edinburgh, identifies the Old Testament as "a collection of authoritative texts of apparently divine origin that went through a human process of writing and editing." He states that it is not a magical book, nor was it literally written by God and passed to mankind. By about the 5th century BC Jews saw the five books of the Torah (the Old Testament Pentateuch) as having authoritative status; by the 2nd century BC the Prophets