alone is used.

The continued existence of a god Bel in the Babylonian pantheon, despite
the amalgamation of Bel with Marduk, is a phenomenon that calls for some
comment. The explanation is to be found in the influence of the
theological system that must have been developed in part, at least, even
before the union of the Babylonian states.[153] Bel, as the god of
earth, was associated with Anu, as the god of heaven, and Ea, as the god
of the deep, to form a triad that embraced the entire universe. When,
therefore, Anu, Bel, and Ea were invoked, it was equivalent to naming
all the powers that influenced the fate of man. They embraced, as it
were, the three kingdoms of the gods, within which all the other gods
could be comprised. The systematization involved in the assumption of a
triad of gods controlling the entire pantheon can hardly be supposed to
have been a popular process. It betokens an amount of thought and
speculation, a comprehensive view of the powers of nature, that could
only have arisen in minds superior to the average intelligence. In other
words, the conception of the triad Anu, Bel, and Ea is again an evidence
of the existence of schoolmen and of schools of religious thought in the
days of the ancient empire. So far, however, as Hammurabi is concerned,
he only refers to a duality--Anu and Bel--which, for him, comprises all
the other gods. He is the 'proclaimer of Anu and Bel.' It is Anu and Bel
who give him sovereignty over the land. In the texts of the second
period the triad does not occur until we come to the reign of a king,
Mili-shikhu, who lives at least eight centuries after Hammurabi. Ea, in
fact, does not occur at all in those inscriptions of the king that have
as yet been discovered. If any conclusion is to be drawn from this
omission, it is certainly this,--that there are several stages in the
development of the ancient theological system of Babylonia. At first a
duality of kingdoms--the kingdom of what is above and below--was
conceived as comprising all the personified powers of nature, but this
duality was replaced by a triad through the addition of the god who
stands at the head of all water-deities. Of course the assumption of a
duality instead of a triad may have been due to a difference among
existing schools of thought. At all events, there seems to be no
political reason for the addition of Ea, and it is difficult to say,
therefore, how soon the conception of a triad standing at the he