Assyrian Monotheism versus Babylonian Pantheism
by Estéban Trujillo de Gutiérrez
“Henceforward “the heaven of Anu” denoted the serene and changeless regions to which the gods fled when the deluge had broken up the face of the lower heaven, and which an Assyrian poet calls “the land of the silver sky.”
It was to this spiritualised heaven that the spirit of Ea-bani, the friend of Gisdhubar, ascended, and from which he gazed placidly on the turmoil of the earth below; and it was from his seat therein that Anu assigned their places in the lower heaven to Samas, Sin and Istar, the Sun, the Moon and the Evening Star, according to the legend of the seven wicked spirits.
But the spiritualisation of Anu did not stop here. As a Semitic Baal he had become a supreme god, the lord and father of the universe. It was only a step further, therefore, to make him himself the universe, and to resolve into him the other deities of the Babylonian pantheon.
We read occasionally in the hymns of “the one god.”
“The ban, the ban,” a poet writes, personifying the priestly sentence of excommunication, like the Ara of Aeskhylos or the divine burden of Zechariah (ix.l),
“is a barrier which none may overpass; the barrier of the gods against which they cannot transgress, the barrier of heaven and earth which cannot be changed; the one god against whom none may rebel; god and man cannot explain (it); it is a snare not to be passed which is formed against the evil, the cord of a snare from which there is no exit which is turned against the evil.”
The conception of Anu, however, as “the one god” was pantheistic rather than monotheistic. The cosmological deities of an older phase of faith were in the first instance resolved into him. In place of the genealogical, or gnostic, system which we find in the account of the Creation in days, we have a pantheistic system, in which Lakhama and the other primeval forces of nature are not the parents of Anu, but are identified with Anu himself.
It is easy to conceive how the old deity An-sar, “the upper firmament,” with all its host of spirits, might be identified with him; but when we find Uras also, the Sun-god of Nipur, made one with Anu, “the hearer of prayer,” and the eagle-like Alala, the bridegroom of Istar and double of Tammuz, equally resolved into the god of Erech, it is plain that we have to do with an advanced stage of pantheism.
This monotheistic, or rather pantheistic, school of faith has been supposed by Sir Henry Rawlinson to have grown up at Eridu; but the fact that it centres round the name of Anu points rather to Erech as its birth-place. How long it flourished, or whether it extended beyond a narrow group of priestly thinkers, we have no means of ascertaining.

Assyrian bas-relief perhaps showing their warrior god Asshur as an Eagle, accompanying Assyrian warriors from the west palace at Nimroud, biblical Calah (p. 214. Austen Henry Layard. A Popular Account of Discoveries at Nineveh. London. John Murray. 1852).
http://www.bibleorigins.net/SundiscEagleAssyrian.html
It is interesting, however, as showing that the same tendency which in Assyria exalted Assur to the position of an all-powerful deity who would brook neither opposition nor unbelief, among the more meditative Babylonians produced a crude system of pantheism.

Austen Henry Layard. A Popular Account of Discoveries At Nineveh. London. John Murray. 1852, p. 211.
http://www.bibleorigins.net/Sundiscarcherdrawnbow.html
Whatever question there may be as to whether the pure and unmixed Semite is capable of originating a pantheistic form of faith, there can be little doubt about it where the Semite is brought into close contact with an alien race. The difference between the Assyrian and the Babylonian was the difference between the purer Semite and one in whose veins ran a copious stream of foreign blood.”
A.H. Sayce, Lectures on the Origin and Growth of Religion as Illustrated by the Religion of the Ancient Babylonians, 5th ed., London, 1898, pp. 190-2.