rituals of worship, and the crucial role of priests, expanding considerably on the role given to Aaron (all Levites are priests, but according to P only the descendants of Aaron were to be allowed to officiate in the inner sanctuary). P's God is majestic, and transcendent, and all things happen because of his power and will. He reveals himself in stages, first as Elohim (a Hebrew word meaning simply "god", taken from the earlier Canaanite word meaning "the gods"), then to Abraham as El Shaddai (usually translated as "God Almighty"), and finally to Moses by his unique name, Yahweh. P divides history into four epochs from Creation to Moses by means of covenants between God and Noah, Abraham and Moses. The Israelites are God's chosen people, his relationship with them is governed by the covenants, and P's God is concerned that Israel should preserve its identity by avoiding intermarriage with non-Israelites. P is deeply concerned with "holiness", meaning the ritual purity of the people and the land: Israel is to be "a priestly kingdom and a holy nation" (Exodus 19:6), and P's elaborate rules and rituals are aimed at creating and preserving holiness. Good cases have been made for both exilic and post-exilic composition, leading to the conclusion that it has at least two layers, spanning a broad time period of 571–486 BCE. This was a period when the careful observance of ritual was one of the few means available which could preserve the identity of the people, and the narrative of the priestly authors created an essentially stable and secure world in which Israel's history was under God's control, so that even when Israel alienated itself from God, leading to the destruction of Jerusalem and the exile in Babylon, atonement could still be made through sacrifice and ritual. Date Julius Wellhausen, the 19th century German scholar who formulated the documentary hypothesis, fixed the chronological order of its sources as the Yahwist and Elohist, followed by the Deuteromist, and last the Priestly. There is currently no general agreement on the absolute dates of any of these sources, but a growing number of scholars place both the Yahwist (the narrative strand) and the Priestly material (a mix of narrative and legal material) in the late Neo-Babylonian or Persian periods. Scope P is responsible for the first of the two creation stories in Genesis (Genesis 1), for Adam's genealogy, part of the