Though at first a religion of the lower classes, it spread rapidly upwards through society, until at the end of the second century A.D. Mithraism became the officially favoured religion of Rome. From this time on Mithraism had a permanent chaplain at court. The Roman emperors, in their programme of self-deification, had already adopted the radiate crown which symbolized the sun, with which Mithraism’s supreme deity, Ahuramazda, was identified. Mithraism was a doctrine to their liking, for Asiatics had always held that the king received his authority from God, by grace, and not, as did the Roman monarch, from the senate, by permission. Aurelian, therefore, identified the Mithraic deity with “Sol Invictus“, the Lord of Hosts, the unconquered sun, which was simultaneously the name of the Emperor. In A.D. 304 Mithra was officially made the protector of Rome, and three years later Diocletian showed his approval by ordering the enlargement of the Mithraeum at Carnuntum.
Rome seemed on the point of being Asiaticized. Many observers have noted the similarity of the court of Diocletian to that of Chosroes I. A flood of Iranian and Semitic conceptions was sweeping the Mediterranean world, threatening to submerge the elaborate culture erected by Greece and Rome. Yet in fifty years Mithraism had collapsed — at the hands of a rival creed whose mythology and ritual were substantially similar, except in one crucial respect. This was Christianity.
The significant feature which both Mithraism and Christianity have in common, but which differentiates them from the previous mystery religions, is that they concern the relationship of a son with a father, not with a mother. The feature which distinguishes them is that, in Mithraism, the son slays the father, symbolized by the bull— a traditional symbol of father deities— while in Christianity the son submits to the father and himself is slain. Mithraism is a religion of conquest, Christianity a religion of submission. In Mithraism aggression is turned outwards (sadism); in Christianity, it is turned inwards (masochism). Mithraism specifically preached that the good lay in action, in conquest, in grappling with the world; Christianity preached that the good lay in passivity, non-resistance. Not surprisingly, Mithraism became the religion of soldiers, administrators and extroverts, but offered no place for women. In contrast Christianity, in the early days, not only attracted introverts but attracted many women and gave them important roles, and also attracted slaves, whom it constantly urged to obey their masters.
In these two myths we may see, as Ernest Jones pointed out long ago, two new solutions for the Oedipus situation; in the first, the son conquers and replaces the father; in the second, he avoids conflict by submitting to him. (139) But to do so he must also deny his own sexual desires. The myth depicts an attempt to avert Oedipal guilt by tabooing sexual activity altogether. And while Mithra survives, Christ dies. The choice of Christianity in preference to Mithraism therefore not only represents a choice of masochism as against sadism, and a turning in of the death instinct against the self, but also a victory for death instincts as against life instincts. Mithraism adopted as its symbol the life-giving sun, the source of energy. Christianity adopted as its symbol the Cross, an instrument of torture and death.