The cult of Mithras affected early Christianity in two fashions. Firstly, although doctrinally speaking it was not one of the most significant impressions, it was vital to the spread and survival of Christianity. It was with Constantine I that Christianity finally became tolerated within the Roman Empire, a window of opportunity through which it was able to ultimitately gain supreme say within the empire to the unfortunate fate of everything deemed un-christian.

Constantine himself was born into the Romanized Mithraic religion of Sol Invictus following in the religion of his father and, indeed, much of Roman at the time. Diocletian who had, for ease of management of an empire too bloated, divided it into two regions, giving caesarship of the Western half to Constantine's father - Constatius - also in religious affairs, contrary to popular monotheistic tendencies of the people, reverted to a worship of the old gods of Zeus, et cetera, although, without dismissing newer deities such as that of Mithras. Diocletians distaste of all that was Christian and opposed the old order of gods, which seems to have been more a politically motivated distate rather than a philosophical or religious one, was epitomized in severe persecutions, the last of which, before his demise, ocurred in C.E. 303.

Constantine's devotion to his religion can be noted when immediately following his father's death, references to the older Zeus-class of gods was removed from the coinage and in their stead were places references to Sol Invictus. Now, to understand Constantine's conversion to Christianity one must understand Constantine himself. Scholars agree that he had a mysticized impression of the Sol Invictus and considered himself doing the bidding of the sun, that is, Mithras. His was a character of confidence, ambition, and drive for success - altho, a man given to calm delicate mannerisms, as was shown several years later in his presence at the Nicean Council. He inhereitted a strong character, yet clear tolerance of the Christian community from his father, under whom, during the purges of Diocletian, the Western half of the empire remained essentially without persecution.

When on the eve of battle in September of C.E. 312 of the Milvian Bridge Constantine found in his dream the visage of Christ approach him, telling him how to act in order to secure victory in the battle the following day, it is clear that Constantine understood this mystical encounter in terms of his own Sol Invictus sending him a messenger in the form of the Christian deity. Having secured victory, Constantine did indeed convert to Christianity, but not upon the virtue of any words the historical Christ may have uttered in his travels in Judea, but in the understanding as Christ a force of victory and triumph in the battlefield and so on. Constantine, upon having received his dream, neither requested baptism nor even indoctrination into any of the rites a new convert would take and, indeed, it would not be until his deathbed that he would receive baptism.

Also, during the schismatic dilemmas during the early 4th century C.E. that the church was suffering through splintering of dogma, Constantine took little interest, only after the trouble had escalated and involved his own districts, following the defeat of Licinius, both his brother-in-law and caecar of the Eastern Empire, did Constantine dispatch letters to the leaders of the opposing Christian camps: that of the Alexander in Egypt, representing the Roman Based Christian faction, and that of the Antiochan based camp of Arius. Even in this letter Constantine's near indifference to the significant arguments concerning Christian doctrine could be seen, which furthers the conclusion that Christianity - namely Christ - for him was no more than a instrument of the one god, Sol Invictus. It can be assumed that he fell back on no other religious background than that which he was born in as obviously his interest in the religious tenets of Christianity was quite lax and the only apparent interest that Christ bore for him was as a deitific messenger of what Constantine understood as his own manifest destiny.

However, even with this personalized interpretation of the Christian god, Constantine's conversion bore two vital results for the Christian community. Firstly, with his Edict of Milan, in 313 C.E. persecution of the Christians was halted, and practice in the faith could go without the fear of governmental retribution; secondly, Constantine's calling of the Nicean Council to dispel strife between various Christian factions allowed for a solidified Christian doctrine to be forged, particularly in the dispelling of various "heretical" movements, and in the construction of the Nicean Creed, which henceforth would herald the trinitarian nature of Christianity and sound as the official testamant of all Christians. This was, however, a crystalizating of only one of the many flavours of Christianity being preeched at this time. It must be understood a canonical New Testamtent although in the working was not formalized yet; there were a score of different Gospels being circulated at the time, each written to appeal to the people of the region in which it was found, and also influenced by various philosophical and religious movements of the time. For instance, when the Gospel of John was written sometime around the end of the 2nd Century C.E. (the earliest mention of the Gospel is in 180 C.E.) it was clearly influenced by Greek philosophical ideas of the "logos" -clearly a very Hellenized work.

Also, Constantine's Mithraic interpretation of the Christ influenced the usage of the symbol of the Cross as a sign of victory and triumph as opposed to one of hulimity and even disgrace that was felt by many of the Christian community - his order for the painting of the Cross onto the shields of his soldiers drove in a deep psychological effect. As influences of Mithraism still deeply resided within the Roman armies, and the Cross, definitely not a symbol distinct to Christianity, but one of much greater antiquity, also was a reminder of Mithras' own sacrifice and ascension unto heaven. And this, both unto the enemies that would oppose Constantine in the battlefield, and for the soldiers fighting under his sovereign word would inflict profound psychological reactions - either that of increased bravery or that of increased fear. And this would in turn, through the boroughs having already been incised by Mithraic belief, allow Christianity yet another avenue by which to engage the hearts of the people.