In the early magical texts "the Zi of heaven" and the "Zi of earth" are invoked to remove the spell that has been cast over the sick or the insane. Even when Ea and his son Asari had taken the place of the demons of the older faith, the official religion was still compelled to recognise their existence and power. The formula of exorcism put into the mouth of Ea himself ends with an appeal to the "life" of heaven and earth. It begins, indeed, with "the charm of Ea," through the efficacy of which the evil spell is to be dissolved; but the charm of the god of wisdom is soon forgotten, and it is to the Zi of heaven and earth that the exorcist finally has recourse. "O life of heaven, mayest thou conjure it; O life of earth, mayest thou conjure it!" thus, and thus only, could the exorcism end. The old associations were too strong to be overcome, and the worshippers of Ea had to allow a place at his side for the "spirits" of an earlier age.
The ancient conception of the Zi lingered long among the Babylonian population. But, as the Semitic element became predominant, it fell more and more into the background, and survived--so far at least as the official religion was concerned--only in a few old formulæ and names. One of the fixed stars, for example, was called Sib-zi-Anna, "the Shepherd of the Life of Heaven," and a common form of oath was by "the life of the gods" or "king" (_nis ilâni_, _nis sarri_). Even Sennacherib swears by "the life of Assur"; but it is questionable whether either he or any of his contemporaries remembered the original meaning and history of the phrase. The Sumerian Zi had received a Semitic translation, and therewith a Semitic connotation. The ideas attached to the Semitic _nêsu_ were not those which had once clustered around the Zi. On the lips of the Semite even the word Zi itself meant "life" and little more. When Pur-Sin II. of Ur, a century or two before Abraham, addresses a dedication in Sumerian to the moon-god, he calls himself "the divine _Zi_ of his country"(220)--in other words, a "god who gives life to his land." There is no question here of a vital force which is the counterpart of a man or god; we have, on the contrary, the Semitic conception of a divine father from whom his people derive their life. The Semite has transferred his own ideas to the language of his Sumerian predecessors, and "life" for him is no materialised reflection of an individual thing, but a principle which is diffused, as it were, from a divine centre. The "Zi of heaven" has become the abstract life, which the god can communicate to those about him.