My heart sinks on the all-too frequent occasions when I am invited to review a book about the Holy Grail. The subject has recently inspired some very silly fantasies and conspiracy theories, in which authors try to demonstrate the "secret truth" of Christianity or claim to have discovered the Grail in the cellar of their family home. Richard Barber, however, has written a serious and useful history of the Grail legend, which should dispel some of the more lunatic theories. He believes that our appetite for this absurd speculation springs in part from our uneasiness with mystery. We want to reassure ourselves that scientific investigation is capable of solving the enigmas of the past.
Barber begins by tracing the origins of the Grail story in medieval literature. The Grail itself has changed its identity over time; it was first seen as the cup used by Christ at the Last Supper, then as the vessel in which Joseph of Arimathea collected the blood of Jesus during the crucifixion; it was also seen as a dish, a chalice containing the Eucharist, and later as a stone or a jewel. However it was envisaged, it was regarded as a gateway to the spiritual world, and became a symbol of the beatific vision of God. It expressed a mysterious reality that was always, tantalisingly, just out of reach.
For the 12th-century poet Chretien de Troyes, the quest for the Grail was just one of many adventure stories associated with the court of King Arthur. Percival, a simple and unsophisticated knight, fails in his quest to find the Grail, which at this point simply represented a knight's progress to maturity. In the 13th century, Wolfram von Eschenbach reinvented the story as a journey towards worldly perfection. When Robert de Boron began to invest the story with greater transcendent significance, Galahad, a more ethereal character, was deemed a more suitable Grail hero.
Barber shows clearly that there was no esoteric meaning lurking behind these tales. The legend seized the imagination of Europe, because it expressed the possibility of spirituality for knights. Monks, priests and hermits are subsidiary characters; it is Galahad, Percival and even the sinful Gawain and Lancelot who seek and sometimes find the Grail. The legend is perhaps similar to the Mahabharata, the ancient Indian epic, which originally expressed the way the warrior class understood the priestly religion of the Vedas. The Grail legends - in their rich variety - showed the vitality of the Christian imagination in pre-Reformation Europe, which felt free to change the Gospel story and give it contemporary resonance.
Barber might perhaps have made a little more of the way this chivalric myth departed from the orthodoxy of the day. In this alone, the Grail legend represents an alternative Christianity. The story took off at the time of the Crusades: instead of the massed armies marching off to the Holy Land, the knights undertook an individual, solitary quest for a more elusive, spiritual goal. Wolfram even makes Percival's half-brother a Muslim. And at a time when western Christianity was becoming increasingly dogmatic, the Grail knights could fulfil their quest only if they were able to break with knightly tradition and ask a question. Wolfram makes Percival ask the wounded Fisher King: "What troubles you?", showing a compassion not much in evidence in the crusading, inquisitorial Church. Wagner would develop this theme in Parsifal.
After the Reformation, there was no appetite for stories that departed so shamelessly from scripture, and it is here that the Grail legend begins to degenerate. From the 18th century, each age interpreted the legend according to its own needs. For German scholars, Wolfram expressed an early German nationalism; in the 19th century, the age of science and technology, Merlin became a free spirit, who gained power through knowledge. Tennyson wrote a Grail story for the Church of England, avoiding difficult questions of dogma and expressing a wary distrust of popery.
The legend was also exposed to dry scholarly analysis. Its origins were found to be Celtic, pre-Christian, Jewish and even Iranian; it became a mythical account of ancient fertility rites or had hidden sexual meaning. All these theories, Barber points out, forgot that the Grail stories were imaginative literature. He then exposes the implausibility of recent Grail literature, with its crazy fantasies involving Mary Magdalene, the Merovingians, Cathars, Templars, Rosicrucians and Freemasons in wildly improbable combinations.
These popular accounts trivialise the rich potential of the Grail myth and reveal a poverty in the modern imagination. So do the archaeological attempts to unearth the "real" Grail, which are as ludicrous as the efforts of the Christian right to discover the "real" Noah's Ark. It seems that we find it almost impossible to think symbolically. An object has no meaning unless we can prove that it once existed physically. Barber is right to suggest that we are uneasy with anything mysterious that defies neat, rational analysis. If a story does not conform to the biblical account, it can have no spiritual value; and if the Bible cannot be shown to be factually true, it is not true at all.
Like "mysticism" and "myth", the word "mystery" comes from the Greek verb musteion: to close the mouth and the eyes. It denotes an experience of obscurity, darkness and silence that is foreign to many of us today. It is symptomatic of our spiritual predicament that we call a detective story a "mystery" because it is of the essence of this genre that the problem is cleared up once and for all. Recent speculations about the Grail often read like bad detective stories, and their popularity suggests a widespread misunderstanding of the nature of religious truth. Barber's subtitle is "Imagination and Belief". We need to recover a sense of the importance of the creative imagination in the religious quest or we will never understand the enduring fascination of the Grail legend, nor the elusive reality that it depicts.
Karen Armstrong is the author of A History of God (Vintage)