From beyond the dawn of humanity, we have been dreaming. But what should we make of those strange hallucinogenic states we fall into night after night? While science can now delineate the physiological aspects of dreaming and show that we experience dreaming during the Rapid Eye Movement (REM) phase of sleep, it provides very little explanation about where dreams come from and what function they serve. People have had such preoccupations for millennia. The earliest thoughts about dreams were recorded on Sumerian tablets in Mesopotamia, now modern Iraq. These dream analyses date back some 5,000 years and show that the Sumerians considered dreams to be messages from the gods, or worse, from demons. They believed that dreams were predictive, either warning of approaching danger, or symptomatic, revealing something about the physical, mental or spiritual health of the dreamer, and descriptions immortalised in an epic Sumerian poem include images of the dreamer embracing an axe, thunderstorms, wild bulls, and a fire- breathing thunderbird. These terrifying dreams were, however, interpreted as good omens.
These beliefs spread through the ancient world and persisted in various guises until modern times. Some might even say that the Mesopotamian concept of dream interpretation continues today amongst the superstitious. It certainly infused into the cultural beliefs of the Egyptians who had sacred healing temples for dreaming and the priests who tended these temples were known as the "Masters of the Mysteries". Dreams were considered divinely inspired and were thought to carry prophecy and guidance. The priests provided advice on state affairs and military campaigns. An Egyptian book dated back to about 1250 BCE, the Chester Beatty Papyrus, is the oldest dream interpretation book in existence. In this text, the dream was first described, for example, "a man sees his bed on fire", next, it was evaluated as 'good' or 'bad' and then interpreted.