The book of Psalms is divided into five separate books. Each one ends with a doxology or a song of praise. Coincidently, it is not understood why Psalms is divided into five books. Some theologians suggest the five-fold division is based on the five books of the torah (Genesis to Deuteronomy). The division of the Psalms is not based on authorship or chronology, as several authors composed the Psalms, and their individual songs are mixed throughout the various passages. The books are split in this way: Book 1: Psalm 1-41, Book 2: Psalms 42-72, Book 3: Psalm 73-89, Book 4 Psalm 90-106, Book 5: Psalm 107-150. There is a group of fifteen Psalms that are called the Songs of Ascent, also called Pilgrim Songs; they consist of Psalm 120-134.
