"historylike", "part of a broader spectrum of originally anonymous, history-like ancient Near Eastern narratives." Scholarly writings frequently refer to Genesis as myth, but there is no agreement on how to define "myth", and so while Brevard Childs famously suggested that the author of Genesis 1–11 "demythologised" his narrative, meaning that he removed from his sources (the Babylonian myths) those elements which did not fit with his own faith, others can say it is entirely mythical. Genesis 1–2 reflects ancient ideas about science: in the words of E.A. Speiser, "on the subject of creation biblical tradition aligned itself with the traditional tenets of Babylonian science." The opening words of Genesis 1, "In the beginning God created the heavens and the earth", sum up the author(s) belief that Yahweh, the god of Israel, was solely responsible for creation and had no rivals. Later Jewish thinkers, adopting ideas from Greek philosophy, concluded that God's Wisdom, Word and Spirit penetrated all things and gave them unity. Christianity in turn adopted these ideas and identified Jesus with the creative word: "In the beginning was the Word, and the Word was with God, and the Word was God" (John 1:1). When the Jews came into contact with Greek thought, there followed a major reinterpretation of the underlying cosmology of the Genesis narrative. The biblical authors conceived the cosmos as a flat disc-shaped Earth in the centre, an underworld for the dead below, and heaven above. Below the Earth were the "waters of chaos", the cosmic sea, home to mythic monsters defeated and slain by God; in Exodus 20:4, God warns against making an image "of anything that is in the waters under the earth". There were also waters above the Earth, and so the raqia (firmament), a solid bowl, was necessary to keep them from flooding the world. During the Hellenistic period this was largely replaced by a more "scientific" model as imagined by Greek philosophers, according to which the Earth was a sphere at the centre of concentric shells of celestial spheres containing the Sun, Moon, stars and planets. The idea that God created the world out of nothing (creatio ex nihilo) has become central today to Islam, Christianity, and Judaism – indeed, the medieval Jewish philosopher Maimonides felt it was the only concept that the three religions shared – yet it is not found directly in Genesis, nor in the entire Hebrew Bible. The