Shoaf gives a good analogy to the concept of the origin of the Holy Grail: "I
believe the usual "take" on the development of Arthurian
legend is that the Holy Grail story was invented by pious Christian
authors precisely to give a Christian shape to the material. The
Arthurian story before that was a tale of military companionship, refined
but passionate adultery, marvels, and worldly glory; add the Grail
history (as devised by Robert de Boron and other authors) and all this
is contrasted with lonely battles against the devil's works, extreme
sexual purity and punishment for sexual sins, miracles, and God's
plan for history. Thus, if a monk wanted to read the Arthur stories,
and a skeptical fellow monk said, "What has Arthur to do with Christ?",
the Grail permitted the reader to expound just what Arthur did have
to do with Christ, salvation history, etc.
Evolution of the
Holy Grail as a Christian Relic
1. The Last Supper described in the
New Testament is the basis of the Christian liturgical service of the
Eucharist. For over 1100 years, the Eucharist was received as bread from a
paten/diskos (or equivalent), sometimes accompanied by wine from a
drinking vessel or chalice. Neither of these was ever called a grail.
One still sees speculation that the origins of the Holy Grail are somehow associated with Albigensian beliefs. The quote below strenuously denies that. A. E. Waite (The Holy Grail, 1933?) wrote (408), "There is only one conclusion to be drawn from the evidence: that the attempt to connect the Catharists, Perfecti, and other Sects of Southern France . . . with the literature of the Holy Grail is a marriage of things which can never be brought together. . . .It is intolerable . . . to propose that the literature of the Holy Grail, though it treats on the surface of Secret Eucharistic Words, of an Arch-Natural Mass and of the most Sacred Relics in all the world of Relics, was committed in reality, but deeply beneath that surface, to the denial and rejection of the Mass and the disdain of Relics."
The Grail is Celtic
There were two blessed articles in the ancient 13 Treasures of Britain, the cors bendegeid - a cornucopia or sacred drinking horn, and the cauldron or platter of plenty. It can be assumed that Chrétien, through whatever source, knew of the articles and his procession has a graal, a deep dish large enough to carry a lamprey or a boar's head or even a human head. I personally do not believe that Chrétien's story is a holy grail story but a story of awakening and familial revenge - a return of the king style story. You can also grasp that during this period of story development and the flowering of the grail stories that there would be confusion, either on purpose or by mistake, where the blessed cup, the cors, becomes the sacred body, the cors or corpus Christi. And suddenly, a cauldron/platter and drinking horn becomes a grail and sacred wafer and even more convoluted becomes a grail cup containing a mass wafer. As the original stories were not Christian mystery stories, the conversion and use of the story elements in the Christianized grail mysteries would create different levels of new stories with the original themes buried within, e.g., such themes as the female grail bearer. Writers use story themes, blending them into their message.
One of the problems that has plagued the connection of the early Grail procession with linkage to the religious grail with its sustaining 'host' or 'communion wafer' and with the cup of the last supper is the fact that the graal was carried by a maiden, a practice that is forbidden by the Church. A solution to this problem has been suggested by way of the Viaticum. In the early Grail stories, the maiden enters and proceeds to the dying king where she provided the host that sustained his life. Among the ancient Greeks, the custom existed of giving a supper to those setting out on a journey, equivalent in Latin of this is viaticus, i.e. "of or pertaining to a road or journey". Subsequently, "viaticum" figuratively meant the provision for the journey of life; and finally, by metaphor the provision for the passage out of this world into the next. It generally meant anything that gave spiritual strength and comfort to the dying and enabled them to make the journey into eternity with greater confidence and security. In the course of time, "viaticum" was applied to the Eucharist; and finally, it acquired its present fixed, exclusive, and technical sense of Holy Communion given to those in danger of death. The Catechism of the Council of Trent (De Euch. sacr., n. 3) says: "Sacred writers call it the Viaticum as well because it is the spiritual food by which we are supported in our mortal pilgrimage, as also because it prepares for us a passage to eternal glory and happiness". As early as 325CE, the Holy Eucharist given to the dying was called the "last and most necessary Viaticum" (Council of Nice, can. 13). Formerly Viaticum was administered not only by bishops and priests, but also by deacons and clerics of inferior orders and even by lay people. From a Decree of the Council of Reims (Regino, "De eccl. disc.", I, cxx), it appears that sometimes even females carried the Viaticum to the dying, which practice the Council strictly forbade. Apparently for a while it was difficult to eliminate this abuse. After the tenth century, no mention is made of lay persons carrying Viaticum to the dying. Even though the practice was eliminated by the time of the compilation of the Grail legends, it does not eliminate the possibility that the earlier versions of the legend could be interpreted in this light, a holy maiden, pure and innocent, carrying the viaticum to the dying king.