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.
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.
The beginning of the downfall of Mithraism dates from A.D.
In the middle of the 3rd century Mithraism seemed on the verge of becoming the universal religion.
The fraternal and democratic spirit of the first communities, and their humble origin; the identification of the object of adoration with light and the Sun; the legends of the shepherds with their gifts and adoration, the flood, and the ark; the representation in art of the fiery chariot, the drawing of water from the rock; the use of bell and candle, holy water and the communion; the sanctification of Sunday and of the 25th of December; the insistence on moral conduct, the emphasis placed upon abstinence and self-control; the doctrine of heaven and hell, of primitive revelation, of the mediation of the Logos emanating from the divine, the atoning sacrifice, the constant warfare between good and evil and the final triumph of the former, the immortality of the soul, the last judgment, the resurrection of the flesh and the fiery destruction of the universe - are some of the resemblances which, whether real or only apparent, enabled Mithraism to prolong its resistance to Christianity.
The symbolism employed by Mithraism finds its best illustration in the large central relief, which represents Mithras in the act of slaying the bull as a sacrifice to bring about terrestrial life, and thus portrays the concluding scenes in the legend of the sacred animal.
Professor Franz Cumont has traced the progress of Mithraism all over the Balkan Peninsula, Italy, the Rhine-lands, Britain, Spain and Latin Africa.
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.
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.