Mithraism was at full maturity on its arrival at Rome, the only modifications it ever suffered having been experienced during its younger days in Asia.
Modified though never essentially changed, (1) by contact with the star-worship of the Chaldaeans, who identified Mithras with Shamash, god of the sun,(2) by the indigenous Armenian religion and other local Asiatic faiths and (3) by the Greeks of Asia Minor, who identified Mithras with Helios, and contributed to the success of his cult by equipping it for the first time with artistic representations (the famous Mithras relief originated in the Pergamene school towards the 2nd century B.C.), Mithraism was first transmitted to the Roman world during the 1st century B.C. by the Cilician pirates captured by Pompey.
From the end of the 2nd century the emperors encouraged Mithraism, because of the support which it afforded to the divine right of monarchs.
Finally, philosophy as well as politics contributed to the success of Mithraism, for the outcome of the attempt to recognize in the Graeco-Roman gods only forces of nature was to make the Sun the most important of deities; and it was the Sun with whom Mithras was identified.
The beginning of the downfall of Mithraism dates from A.D.
- The sources of present knowledge regarding Mithraism consist of the Vedas, the Avesta, the Pahlevi writings, Greek and Latin literature and inscriptions,.
- The rapid advance of Mithraism was due to its human qualities.
- The most interesting aspect of Mithraism is its antagonism to Christianity.
Mithraism courted the favour of Roman paganism and combined monotheism with polytheism, while Christianity was uncompromising.
In the middle of the 3rd century Mithraism seemed on the verge of becoming the universal religion.
Manichaeism, which combined the adoration of Zoroaster and Christ, became the refuge of those supporters of Mithraism who were inclined to compromise, while many found the transition to orthodox Christianity easy because of its very resemblance to their old faith.
Towards the close of the 3rd century two great religions stood opposed to one another in western Europe, one wholly Iranian, namely Mithraism, the other of Jewish origin, but not without Iranian elements, part and parcel probably of, the Judaism which gave it birth, namely Christianity.
Professor Franz Cumont has traced the progress of Mithraism all over the Balkan Peninsula, Italy, the Rhine-lands, Britain, Spain and Latin Africa.
A missionary religion like Mithraism, which established itself all the way from Western Asia to the borders of Scotland, was certainly not " national."
The cumbrous mythology and cosmogony of Mithraism at last weakened its hold upon men's minds, and it disappeared during the 4th century before a victorious Catholicism, yet not until another faith, equally Iranian in its mythology mad cosmological beliefs, had taken its place.
This new faith was that of Mani, which spread with a rapidity only to be explained by supposing that Mithraism had prepared men's minds for its reception.