5. The Pentateuch is no longer assigned in its entirety to Moses; it is thought, rather, to contain material selected from four different sources, which the compiler had before him in writing.[16] These documents did not reach their final form until some time subsequent to Moses, but all of them contained ancient material, much of it going back to the time of Moses, some of it even to pre-Mosaic days. Among the contents of the Pentateuch special attention is called to three legal codes--the Book of the Covenant, the Deuteronomic Code, and the Priestly Code--belonging to different periods in Hebrew history, and reflecting different stages in the religious and social development of the nation. The Deuteronomic Code, in some form, is believed to have been the basis of the reforms instituted by Josiah {89} and to have been written most probably during the early part of the seventh century. On these general questions respecting the Pentateuch there seems to be general agreement among critical scholars; on the other hand, there is wide divergence of opinion concerning points of detail, such as the chronological order in which the several documents reached their final form, their exact dates, the manner and time of their compilation, the detailed distribution of the material among the several sources, etc. The differences of opinion on these points are due to the fact that the data upon the basis of which the problems must be solved are not sufficiently numerous or decisive. 6. Doubt is thrown upon the authorship of a number of Old Testament books, or parts of books, which have been assigned to certain authors by both Jewish and Christian tradition. As already stated, the Mosaic authorship of the Pentateuch is denied; the book of Lamentation is taken away from Jeremiah; parts of Isaiah and Zechariah and the whole of Daniel are assigned to persons other than the prophets bearing these names. The accuracy of the psalm titles is questioned; few of the psalms, if any, are assigned to David or his age; and most of the psalms--by some scholars all--are placed in the post-exilic period. A conservative scholar, like W. T. Davison, is not willing to say more than "that {90} from ten to twenty psalms--including 3, 4, 7, 8, 15, 18, 23, 24, 32, and perhaps 101 and 110--may have come down to us from David's pen, but that the number can hardly be greater, and may be still less."[17] The same uncertainty is believed to exist respecting the authorship of Proverbs and of Ecclesiastes, which is considered one of the latest books in the Old Testament canon. Other books, like Job, which in the absence of external testimony were formerly assigned to an early date, are now placed in the later period of Hebrew history.