The Psalter has plainly had a long history. In its present form it obviously rests upon groups, which in turn rest upon individual psalms, that are no doubt often far older than the groups in which they stand. Like the Pentateuch, and perhaps in imitation of it, the Psalter is divided into five books, whose close is indicated, in each case, by a doxology (xli., lxxii., lxxxix., cvi.), except in the case of the last psalm, which is itself a doxology (cl.). This division appears to have been artificially effected. Psalm cvii., which starts the last book, goes naturally with cv. and cvi., which close the fourth book; and the circumstance that the number of psalms in the fourth book corresponds exactly with that of the third, raises a strong suspicion that the break was deliberately made at Psalm cvi. It is very probable, too, that the doxology at the close of Psalm cvi. (cf. 1 Chron. xvi. 36), which differs somewhat from the other doxologies, was originally intended as a doxology to that psalm only, and not to indicate the close of the book. In any case, the contents of books 4 and 5, which are very largely liturgical, are so similar that they may be practically considered as one book. Books 2 and 3 may also be similarly regarded; for whereas in books 1, 4 and 5 the name of the divine Being is predominantly Jehovah, in books 2 and 3 it is predominantly Elohim (God), and there can be no doubt that these two books, at least as far as Ps. lxxxiii., have been submitted to an Elohistic redaction. Psalm xiv., _e.g._, reappears in the 2nd book as Psalm liii. in a form practically identical, except for the name of God, which is Jehovah in the one (xiv.) and Elohim in the other (liii.); the change is, therefore, undoubtedly deliberate. This is also made plain by the presence of such impossible phrases as "God, thy God," xlv. 7, 1. 7, instead of the natural and familiar "Jehovah, thy God." Whatever the motive for the choice of this divine name (Elohim) may be, it is so thoroughly characteristic of books 2 and 3 that they may not unfairly be held to constitute a group by themselves. In this way the Psalter falls into three great groups--book I (i.-xli.), which is Jehovistic, books 2 and 3 (xlii.-lxxxix.), which are Elohistic, and books 4 and 5 (xc.-cl.), which are Jehovistic..