In the beginning there is only one god. Because of the sinful nature of men, they have created many gods (eg. trees, plants, animals, nature, rocks, human beings, ancestors, all kinds of idols and creatures; and bow down to worship them. Therefore, God destroyed (except Noah & his family who were faithful to God and selected pair of each animals) the earth by a great flood. So that mankind can have a new beginning with Noah n his family. However n subsequently, human beings repeated the same mistakes again as before. So, God had to choose a group of people which he called the Israelites n gave them the laws, decrees n commandments to follow.