Now, about the Holy Grail ...
Richard Barber's book The Holy Grail presents the history of a concept. That's a daring thing to do when the concept's origins are hotly disputed. Barber makes a convincing case for the purely Christian origin of the story of the Holy Grail, linking the Grail to debates about the nature of the Eucharist and changes in the ritual's form dating from the end of the twelfth century — in other words, at exactly the same time as the Grail began to appear in the romances of King Arthur. Claims of a Celtic origin for the Grail story are dealt with, but in later chapters.
So Barber begins with Chrétien de Troyes and medieval Arthurian romance; slightly more than half the book is a close reading of the images of the Grail presented in these texts. Barber's essential point is that Chrétien was the first writer to begin a story of the Holy Grail, but that Chrétien left his Grail story uncompleted — which meant that later writers, attracted by the idea, used the Grail as a story element without really knowing what Chrétien would have done with it. In other words, they had to make up their own story and their own meaning for the image of the Grail. Naturally, therefore, stories and meanings proliferated.
Barber traces some of these stories and meanings as he traces the development of the idea of the Holy Grail forward in time from the twelfth century to the edge of the twenty-first. He looks at Wolfram von Eschenbach, at Thomas Malory, and then hits a period in the seventeenth and eighteenth centuries where Grail stories began to fall out of favour. After which Barber finds a gradual rebirth of Arthurian romance; but a rebirth with some curious ideas about its ancestry.
The concept of pagan and Celtic origins for the Grail are considered as Barber's story moves through the nineteenth and twentieth centuries. His argument here is, essentially, that real scholarship on the Grail was corrupted during much of this time by various ahistorical ideas — including nationalism, occultism, a cod-Jungian insistence on the power of archetypes, and a generally hazy sense of the context of many of the original texts. Barber goes some distance to proving his point by ably deconstructing some very fuzzy thinking from older writers.
In a sense, then, this book is part of an ongoing historiographical process in which a complex of ideas surrounding the oral transmission of religious or folkloric ideas in Europe is coming into question; one thinks of Ronald Hutton's works, such as Seasons of the Sun and Triumph of the Moon. It's interesting work, digging not only into resonant ideas (like the Holy Grail), but also into the odd shapes that imagination and twists these ideas. It's work that is by its nature part of a dialogue, analysing and revising preceding interpretations — therefore implying that the current interpretation itself will one day be analysed and perhaps altered.
This is the real problem with conspiracy theories like Holy Blood, Holy Grail (and Barber considers these in his survey of Grail-related notions, as well). Conspiracy theories live by faith. Once a few vaguely-connected notions are put together in an ill-fitting jigsaw, then questioning any part of the overall construction becomes a heretical attack on the whole. Unless the questioning can be seen as an expansion, extrapolating from the original revelation out to ever-weirder areas. Actual examination of source documents or historical context is frowned on. Barber, whose book largely consists of a careful examination of source documents and historical contexts, does a decent job of pointing out some of the obvious problems with these more fantastical ideas of the Grail, but wisely refrains from growing too involved.
Having said that, I did find that the original Grail idea, as Barber describes it, was less intriguing than the developments and mutations it went through in succeeding centuries. That's not because of claims for the historical actions of the Grail or of some order of Grail knights, though; it's because, as Barber himself points out, the Grail has been the subject of some fascinating literary treatments. Barber's survey of these writings may not be thorough — simply too many tales have been told about the Grail for that — but he has a fine eye for which works to mention. I give him special credit for his excellent discussions of John Cowper Powys' A Glastonbury Romance and of the work of Charles Williams. Barber's own work recalls Williams' prose writings on the development of the Grail and Arthur myths; like Barber, Williams argued strongly for a purely Christian origin to the Grail, discounting notions of Celtic influence.
Barber notes that he's an agnostic, and expected to spend more time dealing with Celtic stories and mythological precursors for the Grail. But his research led him to reconsider his old ideas. This is history as it should be written, then; history as science, where the historian's opinion changes as the facts come to light. I don't think this book is the final word in the history of the Grail. But it is a remarkable step forward.