One of the most popular religions of the Roman Empire, especially among Roman soldiers, was Mithraism. Its origins are Persian, and involves their ancient hierarchy of gods, as restructured by Zarathustra (c. 628-c. 551 bc) in the holy books called the Avestas.

The universe was seen as involved in an eternal fight between light and darkness, personified by Ahura-Mazda (good) vs. Ahriman (evil). This idea probably influenced Jews while they were in Babylon, which is when they adopted HaShatan -- Satan -- as the evil one!

Within the Persian pantheon, Mithra was “the judger of souls” and “the protector,” and was considered the representative of Ahura-Mazda on earth.

Mithra, legend says, was incarnated into human form (as prophesized by Zarathustra) in 272 bc. He was born of a virgin, who was called the Mother of God. Mithra's birthday was celebrated December 25 and he was called “the light of the world.” After teaching for 36 years, he ascended into heaven in 208 bc.

There were many similarities with Christianity: Mithraists believed in heaven and hell, judgement and resurrection. They had baptism and communion of bread and wine. They believed in service to God and others.

In the Roman Empire, Mithra became associated with the sun, and was referred to as the Sol Invictus, or unconquerable sun. The first day of the week -- Sunday -- was devoted to prayer to him. Mithraism became the official religion of Rome for some 300 years. The early Christian church later adopted Sunday as their holy day, and December 25 as the birthday of Jesus.

Mithra became the patron of soldiers. Soldiers in the Roman legions believed they should fight for the good, the light. They believed in self-discipline and chastity and brotherhood. Note that the custom of shaking hands comes from the Mithraic greeting of Roman soldiers.

It was operated like a secret society, with rites of passage in the form of physical challenges. Like in the gnostic sects (described below), there were seven grades, each protected by a planet.

Since Mithraism was restricted to men, the wives of the soldiers often belonged to clubs of Great Mother (Cybele) worshippers. One of the women’s rituals involved baptism in blood by having an animal- preferably a bull - slaughtered over the initiate in a pit below. This combined with the myth of Mithra killing the first living creature, a bull, and forming the world from the bull's body, and was adopted by the Mithraists as well.

When Constantine converted to Christianity, he outlawed Mithraism. But a few Zoroastrians still exist today in India, and the Mithraic holidays were celebrated in Iran until the Ayatollah came into power. And, of course, Mithraism survives more subtly in various European -- even Christian -- traditions.