ATUM was the creator god of Heliopolis, the sole progenitor and head of the ancient Egyptian pantheon according to one of the earliest Egyptian cosmogonies. Atum, "the all" or "the complete one," by spitting, vomiting, or masturbating produced Shu and Tefnut, "air" and "moisture," who in turn generated Geb and Nut, "earth" and "sky." This last chthonic pair produced Osiris and Seth, rivals for the rulership of the land, together with their consorts, Isis and Nephthys. Together these nine deities comprised the great Heliopolitan ennead, but probably the greatest function of this pantheon was to provide a genealogy for the Egyptian king, who was equated with Horus, the son of Isis. Horus had to avenge the slaying of his father, Osiris, by his uncle, Seth.
As early as the Old Kingdom (2686–2181 bce) the sky god, Atum, had been assimilated to the sun god, Re. This new solar deity, Re-Atum, gained or regained a commanding position at the head of the Egyptian pantheon and contributed to some weakening in the myth of divine kingship by clearly subordinating the king to the god by the fifth dynasty. However, the Horus-king was accommodated to the new solar cult by being titled also "Son of Re." At some point the creator god, Atum, was subordinated to Ptah, at least by Memphite priests who described Atum's creation by Ptah as recorded on the Shabaka Stone.
The great temple of Heliopolis, one of the three largest in Egypt, has not survived, and very few finds have been made in its vicinity. The vast amount of religious literature whose origin was Heliopolitan was primarily solar-oriented and had Re as principal god, but the sources are from the fifth dynasty and later. In the solar religion Atum was retained as the old, setting sun, and Khepri was the young, rising sun, but Re was the bright noonday sun. It is probably impossible to estimate the earlier importance of Atum or of the later revivals that may have reawakened interest in this primordial god. The late Contendings of Horus and Seth presents Atum as one of the chief judges before whom most of the other senior deities testify on behalf of Horus, while Seth appears to have had the support of the supreme god Re.
The two volumes of Studien zum Gott Atum (Hildesheim, 1978–1979), edited by Karol Mysliwiec as volumes 5 and 8 of the "Hildesheimer ägyptologische Beiträge," offer comprehensive coverage.
Leonard H. Lesko (1987)