How the early Christians described the mysteries
When we enter the Christian era, the Eleusinian mysteries do not immediately die out. The mysteries were especially prominent in the Empire under Julian (361-363) and also by the Neo-Platonists. Even an edict issued by Valentinian I and Valens (364-375) did not harm them; it was only with the destruction of Eleusis by Christian monks in 395-96 that the mysteries ended. Because the rites lingered for so long, and because they were such an important part of ancient society, the early Christians were forced to deal with them, and they did so in various ways.
Surprisingly, even among the Christian converts who had previously gone through initiation, we do not find any more specific, reliable information concerning the rites - apparently, even after converting they felt bound by the vow of secrecy they had made. And although we find plenty of testimonies about the ceremonies in the writings of the Fathers of the Church, it is important to be skeptical in our consideration of them since the Fathers viewed the rites with such contempt. In fact, none of the Fathers had ever been initiated at all.
When we do find the mysteries mentioned by the Fathers, often this was done in a very hostile manner. Apologetic writers such as Tertullian accuse the mysteries of being "diabolical apings of Christian truths." St. Augustine also attacks the Eleusinian mysteries, based primarily on what was written about them by Varro. He criticizes the inconsistencies of the myth behind the rites. For example, in City of God he notes that Persephone is represented in varying ways: "…according to a variant opinion in the same book, she is not the fertility, but the lower regions of the earth." If the myth itself is so unreliable, he asks, how can we place any trust in the mysteries which imitate it?
Perhaps one reason the Fathers attacked the rites so bitterly was because there were many general resemblances between the mysteries and early Christian ritual, similarities such as fasting and congregational worship led by a minister. Other similarities include the ideas of salvation, the worship of a pure God, the living of a pure life, and the cultivation of brother love. Some scholars believe that Catholicism owes many of its practices to the mystery religions.
However, it is not only the rituals of the Church that resembled the mystery rites; even the vocabulary of some of the Fathers became quite similar. This was probably done in order to put the non-Christians at ease. Clement of Alexandria states, "I will give you understanding of the mysteries of the Logos by means of images with which you are familiar." Indeed, his language is filled with technical terms from the rites, so convincingly that it is quite difficult to completely understand for those of us unfamiliar with the rites:
Oh! mysteries truly holy! Oh! Stainless light! The daduchs lead me on to be the epapt of the heavens and of God; I am initiated and become holy; the Lord is the hierophant and seals the mystes for himself, himself the photagogue.
Clement is not the only Christian writer using this method. Such a technique can be found in the writings of Paul and Ignatius, among others. In fact, in Greek sermons the phrase "this is known to the initiates" is quite common; and the Pseudo-Areopagite warns the initiated Christian who has passed through the "mystagogia" against careless talk. Such language no doubt attracted many pagans who were very comfortable and acquainted with such terms; it also shows us just how prevalent the influence of the mysteries must have been in ancient society.
By now it has become evident that the Eleusinian mysteries were extremely powerful, not only in a pagan world but more incredibly, in an era of Christianity as well. The fact that the mysteries survived so long suggests that they must have offered something to the initiates. What is so unfortunate is the fact that we will most likely never get any closer to a fuller understanding of the mysteries than that which we possess today. The complete secrecy that prevents us from getting closer to these rites is at the same time a testimony to the power that they must once have had.