Babylonian astrology was the first known organized system of astrology, arising in the second millennium BC. In Babylon as well as in Assyria as a direct offshoot of Babylonian culture, astrology takes its place as one of the two chief means at the disposal of the priests (who were called bare or "inspectors") for ascertaining the will and intention of the gods, the other being through the inspection of the livers of sacrificial animals (see omen). Early origins There is speculation that astrology of some form appeared in the Sumerian period in the 3rd millennium BC, but the isolated references to ancient celestial omens dated to this period are not considered sufficient evidence to demonstrate an integrated theory of astrology. The history of scholarly celestial divination is therefore generally reported to begin with late Old Babylonian texts ( 1800 BC), continuing through the Middle Babylonian and Middle Assyrian periods ( 1200 BC). By the 16th century BC, the extensive employment of omen-based astrology can be evidenced in the compilation of a comprehensive reference work known as Enuma Anu Enlil. Its contents consisted of 70 cuneiform tablets comprising 7,000 celestial omens. Texts from this time also refer to an oral tradition – the origin and content of which can only be speculated upon. At this time Babylonian astrology was solely mundane, and prior to the 7th century BC the practitioners' understanding of astronomy was fairly rudimentary. Because of their inability to accurately predict future celestial phenomena and planetary movement very far in advance, interpretations were done as the phenomena occurred or slightly before. By the 4th century, however, their mathematical methods had progressed enough to calculate future planetary positions with reasonable accuracy, at which point extensive ephemerides began to appear. Divinatory basis The history of Babylonian astrology shows the development of astronomical knowledge within the context of divination. A collection of 32 tablets with inscribed liver models, dating from about 1875 BC, are the oldest known detailed texts of Babylonian divination, and these demonstrate the same interpretational format as that employed in celestial omen analysis. Blemishes and marks found on the liver of the sacrificial animal were interpreted as symbolic signs which presented messages from the gods to the king. The gods were also believed to present themselves in the celestial images of the planets or stars with whom they were associated. Evil celestial omens attached to any particular planet were