St. George Decoded - The Cult of Mithras, page 14
I am indebted to David Ulansey's book "The Origins of Mythraic Mysteries" in which he opened up the inner core of Mithraic beliefs. A number of misconceptions are extent about the inner mysteries of this religion. Mithra was a Persian deity and is thus seen to be a Persian belief system that found its favour with the Romans from about the first century BC. It was a mystery religion whose inner truths were revealed to the acolyte as he proceeded through the levels until the core revelation was laid out before him. I say 'he' and 'him' as women were specifically excluded from membership of the cult. It was especially favoured by Romans serving the state, like soldiers and functionaries. (The historical George was just the sort of functionary who could have been a Mithraist before his conversion to Christianity.) The Mithraic Cult spread widely from its place of origin in the Near East and found itself practised in many corners of the Empire. It had no gospel, and left no written system of theology. Quite what it represented had remained largely a mystery. They did leave behind, however, a rich resource of graphic images in their temples.
Ulansey showed that the godhead of this religion was not Persian at all. They worshipped the Greek god Perseus. For a mystery religion, what better than to hide the true identity of its godhead behind another tradition. It seems that the cult was astronomical in nature and its theology was written in the constellations of the night sky. Its core revelation embodied a discovery by a Greek astronomer called Hipparchos in about 120 BC. He had been studying ancient Babylonian star tables and noticed that since the tables had been compiled the positions of the stars with respect to the sun had changed. He came to the conclusion that the starry dome above us, once believed to be fixed, eternal, and immutable, was in fact in motion. Such a conclusion finding its way into general society must have thrown into doubt the eternal and infallible nature of the gods themselves. Into that uncertainty stepped the cult of Mithras, which had a complete explanation for the mysterious shifting of the eternal starry domain of the gods above.
The revelation of the Mithraists was that the Greek hero Perseus was in fact far more powerful than the pantheon of all the existing Roman gods put together, for it was he who had the strength and the power to shift the universe in just such a fashion. Perseus is shown symbolically in battle with Taurus the Bull, see the figure below1. This represents the force that shifted the starry dome from its relationship with the Sun. What Hipparchos had discovered, and what the cult of Mithras adopted, was an astronomical phenomenon visible only from the surface of the Earth called 'precession of the equinoxes', of which more later. He must have been a mighty powerful god to wrench apart the very fabric of the universe. Who could not acknowledge such a powerful deity?
1In these discussions we are dealing with allegory, that is, the constellations involved represent figures in a story, or some physical process. Nobody actually says that the constellation of Perseus rushed across the sky and battled the constellation of Taurus like some Battle of Britain dogfight over the fields of Kent.