A pagan religion consisting mainly of the cult of the ancient Indo-Iranian Sun-god Mithra. It entered Europe from Asia Minor after Alexander's conquest, spread rapidly over the whole Roman Empire at the beginning of our era, reached its zenith during the third century, and vanished under the repressive regulations of Theodosius at the end of the fourth century. Of late the researches of Cumont have brought it into prominence mainly because of its supposed similarity to Christianity.
The origin of the cult of Mithra dates from the time that the Hindus and Persians still formed one people, for the god Mithra occurs in the religion and the sacred books of both races, i.e. in the Vedas and in the Avesta. In Vedic hymns he is frequently mentioned and is nearly always coupled with Varuna, but beyond the bare occurrence of his name, little is known of him (Rigveda, III, 59). It is conjectured (Oldenberg, "Die "Religion des Veda," Berlin, 1894) that Mithra was the rising sun, Varuna the setting sun; or, Mithra, the sky at daytime, Varuna, the sky at night; or, the one the sun, the other the moon. In any case Mithra is a light or solar deity of some sort; but in vedic times the vague and general mention of him seems to indicate that his name was little more than a memory. In the Avesta he is much more of a living and ruling deity than in Indian piety; nevertheless, he is not only secondary to Ahura Mazda, but he does not belong to the seven Amshaspands or personified virtues which immediately surround Ahura; he is but a Yazad, a popular demigod or genius. The Avesta however gives us his position only after the Zoroastrian reformation; the inscriptions of the Achaemenidae (seventh to fourth century B.C.) assign him a much higher place, naming him immediately after Ahura Mazda and associating him with the goddess Anaitis (Anahata), whose name sometimes precedes his own. Mithra is the god of light, Anaitis the goddess of water. Independently of the Zoroastrian reform, Mithra retained his place as foremost deity in the north-west of the Iranian highlands. After the conquest of Babylon this Persian cult came into contact with Chaldean astrology and with the national worship of Marduk. For a time the two priesthoods of Mithra and Marduk (magi and chaldaei respectively) coexisted in the capital and Mithraism borrowed much from this intercourse. This modified Mithraism traveled farther north-westward and became the State cult of Armenia. Its rulers, anxious to claim descent from the glorious kings of the past, adopted Mithradates as their royal name (so five kings of Georgia, and Eupator of the Bosporus). Mithraism then entered Asia Minor, especially Pontus and Cappadocia. Here it came into contact with the Phrygian cult of Attis and Cybele from which it adopted a number of ideas and practices, though apparently not the gross obscenities of the Phrygian worship. This Phrygian-Chaldean-Indo-Iranian religion, in which the Iranian element remained predominant, came, after Alexander's conquest, in touch with the Western World. Hellenism, however, and especially Greece itself, remained remarkably free from its influence. When finally the Romans took possession of the Kingdom of Pergamum, occupied Asia Minor and stationed two legions of soldiers on the Euphrates, the success of Mithraism in the West was secured. It spread rapidly from the Bosporus to the Atlantic, from Illyria to Britain. Its foremost apostles were the legionaries; hence it spread first to the frontier stations of the Roman army.
Mithraism was emphatically a soldier religion: Mithra, its hero, was especially a divinity of fidelity, manliness, and bravery; the stress it laid on good fellowship and brotherliness, its exclusion of women, and the secret bond amongst its members have suggested the idea that Mithraism was Masonry amongst the Roman soldiery. At the same time Eastern slaves and foreign tradesmen maintained its propaganda in the cities. When magi, coming from King Tiridates of Armenia, had worshipped in Nero an emanation of Mithra, the emperor wished to be initiated in their mysteries. As Mithraism passed as a