The Greek gods were created by man to explain the world around them, act as a means of exploration, provide legitimacy and authority to ancient Greek aristocracy, and provide entertainment for the masses. The religion of the ancient Greeks did not have a single source of written scripture such as the Bible or the Qur'an. Furthermore, the ancient Greeks did not believe in absolute truth as practiced by modern faiths such as Christianity and Judaism. Generally, a Greek city-state would devote itself to a particular god or a set of gods, and depending on the location of the city-state, the characteristics of the gods could vary widely. Many city-states erected temples to their particular gods, and these gods were honored in festivals and animal sacrifices. The ancient Greek gods normally took on human form and lived in a society similar to human society. They exhibited all the emotions of human beings and frequently intervened in human history. The most significant difference between the Greek gods and humans was that the gods were immortal and human beings were not.