My dissertation talks a lot about early Alexandrian Christianity, both as an important influence on Christian Platonism and as an issue that was debated in Joseph Smith’s day (was it good or bad?) An intriguing aspect of Alexandrian Christianity was the secret tradition or secret discipline. Here’s a passage from my dissertation.
Many fathers did talk about a secret tradition, most notably Clement of Alexandria. Eusebius quoted from Clement’s Hyptotyposes: “The Lord after his resurrection imparted knowledge to James the Just and to John and Peter, and they imparted it to the rest of the apostles, and the rest of the apostles to the seventy, of whom Barnabas was one.” Clement frequently used the language of the mysteries when speaking of the higher truth. “The mysteries are not exhibited incontinently to all and sundry,” explained Clement, “but only after certain purifications and previous instructions.” Clement alluded to practicing “greater” and “lesser” mysteries, similar to Eleusis. Clement declared, we “shall address ourselves to the true gnostic science of nature, receiving initiation into the minor mysteries before the greater.” In the “Letter to Theodore,” Clement spoke of a “more spiritual Gospel” of Mark “for the use of those who were being perfected. Nevertheless,” continued Clement, Mark “did not divulge the things not to be uttered, nor did he write down the hierpahantic teaching of the Lord.” Instead Mark “brought in certain sayings of which he knew the interpretation would, as a mystagogue, lead the hearers into the innermost sanctuary of the truth hidden by seven veils.” Mark left the more spiritual gospel with the church in Alexandria, said Clement, “where it even yet is most carefully guarded, being read only to those who are being initiated into the great mysteries.” As Clement said in the Stromata, “The Saviour Himself, then, plainly initiates us into the mysteries.”
Other early fathers spoke of the secret tradition after Clement. To Celsus’s charge that Christians did not teach certain things openly, Origen said Jesus, the apostles, and prophets, “saw better than Plato (by means of the intelligence which they received by the grace of God), what things were to be committed to writing, and how this was to be done, and what was by no means to be written to the multitude, and what was to be expressed in words, and what was not to be so conveyed.” Basil, quoted above, spoke of rites coming from the secret tradition in the fourth century and Pseudo-Dionysius made similar comments in the fifth or sixth century. Dionysius said that “the first leaders or our hierarchy … in their written and unwritten initiations … brought the transcendent down to our level.” He also spoke of being “initiated in the sacraments of the sacred mystagogy by our hierarchy’s mysteries and traditions” but warned, “see to it that you do not betray the holy of holies.… Keep these things of God unshared and undefiled by the uninitiated.”
In the following weeks, I’m going to put up a series of posts on stuff related to the secret tradition. I don’t pretend to be an expert on the topic, but find the topic very interesting and want to share some of the things that I’ve found. I’d be very interested to hear from those with more expertise.
 Eusebius, Church History, 2.1.4
 Clement, Stromata, 5.4; 5.11; 4.1.
 Clement of Alexandria, “Letter to Theodore,” in The Ancient Mysteries: A Sourcebook of Sacred Texts, ed. Marvin W. Meyer (Philadelphia: University of Pennsylvania Press: 1987), 233. Clement’s “Letter to Theodore,” remains controversial, though Scott Brown’s extensive research on the work declares it authentic and cites a number of scholars who agree. Scott G. Brown, Mark’s Other Gospel: Rethinking Morton Smith’s Controversial Discovery (Waterloo, Can.: Wilfrid Laurier University Press, 2005). Guy Stromousa asserts that Clement’s letter to Theodore states “in no ambiguous terms the existence of esoteric doctrines, relating to the teaching of Jesus, in the Alexandrian church,” and also notes that “in the Eclogae Propheticae, Clement refers to certain books kept secret by the Christian gnostikoi in Alexandria.” Guy G. Stromousa, Hidden Wisdom: Esoteric Traditions and the Roots of Christian Mysticism, 2d ed. (Leiden: Brill, 2005), 71.
 Clement, Stromata, 4:25.
 Origen, Against Celsus, 6.6
 Pseudo-Dionysius, Ecclesiastical Hierarchy, 1.5; 1.1. Dionysius referred to these rites as “theurgy,” 1.1.