But Babylonia itself was a dual State. It was probably on this account that Lugal-zaggi-si had fixed his capital at Erech in the centre of the country, midway between north and south. And the gods of Northern Babylonia were not necessarily those of the south. Here Ea was at the head of the divine host; for the south his city of Eridu was what Nippur was for the north, and the same causes which made Bel the dispenser of power to the northern princes, made Ea the guardian and guide of the monarchy in the south. For their worshippers Bel and Ea stood on the same level; the cult of each alike had descended from a remote antiquity, and their priests exercised a similar influence and power. As the Babylonians of the north were called the people of Bel whom Bel could grant to whom he would, so too the mixed races of the south were the creation of Ea to whom the god of Eridu had taught the arts of life.
The union of north and south consequently brought with it the formation of a divine triad. Ea joined himself to Bel and Anu, and the supreme triad of Anu, Bel, and Ea thus came into existence. The process of formation was facilitated by the fact that the three gods were already distinguished from one another in their main features. Anu was the god of the sky; the earlier history of Bel had given him naturally the dominion of the earth; and though, in becoming a Semitic Baal, he had acquired the attributes of a god of the upper sphere, these were allowed to fall into the background. Ea was even easier to deal with; his home was in the deep, and his rule was accordingly confined to the waters and the sea. That he had once been a god of the land as well as of the sea, was dropped out of sight, and in the later centuries of Babylonia it even began to be forgotten that he had created man out of the dust of the ground. He ceased to be the divine potter, and became instead the god of the waters, who pours out the Tigris and Euphrates from the vases in his hands. As god of the earth and the living things upon it, his place was taken by his son. Asari, transformed into the Semitic sun-god Merodach, became the inheritor of his father's wisdom, and therewith of his father's power.
The formation of the Babylonian triad, and the differentiation of the divine persons who composed it, must have been the work of a theological school. It is an artificial scheme elaborated after the union of the northern and southern parts of the country. The universe is divided between the three divine representatives of Northern, Central, and Southern Chaldæa, whose sanctuaries were the oldest in the land, and whose cult had been handed down from time immemorial. The triad once formed became a model after which others could be created. The other great gods followed the example that had been set them, and were similarly resolved into triads. As the orthodox theological system of Egypt rested on the Ennead, the corresponding Babylonian system rested on the triad. The principle in each case was much the same. The Ennead was but a multiple of the triad, and presupposed the sacred number. Perhaps we may see in it the result of a contact between Sumerian modes of thought and the Semitic conception of the divine family. Where the god had a wife and a son, the godhead would naturally be regarded as a trinity.(245)