The Grail represents a private, personal journey for enlightenment and power. It is fundamentally a shaman's quest, not the path for Catholic saints. Relying on visionary experience and miraculous/magical adventures with otherworldly beings of ambiguous morality, the seeker enters a world too loosely structured for the rigid dichotomies that were fast characterizing Christian thinking. The Grail world contains shape shifting powers, were friendly foes become foe-like friends. It is true the world of the unconscious, where the conscious mind's binary categories fail to explain reality. Black and white, good and bad, ally and enemy, sacred and profane, are not easily distinguished. The Grail is a cup, not a box. There are no separate corners for saints and sinners. On the contrary, the Grail, like its pagan antecedent, the Cauldron of Mystery, contains a heady, hallucinatory brew of seekers, fools, risk-takers, failures, and fighters. Its healing power satisfies each person in terms of what he or she needs most for self-discovery. If we dare to look into the round, spherical vessel of the Grail, we become, like its contents, stirred, mixed, and intermingled, losing our sense of separateness. For ultimately, that is the lesson of self-discovery; we are not separate, but part of the whole.
Thought provoking, even. While I differ with Tom on some metaphysical conclusions that he draws, from a Gamesmaster's point of view this all makes for fascinating source material. I see entire campaign worlds in this one paragraph. For this reason I recommend "Fire in the Head" for Gamesmasters. The ideas percolating through the work are fascinating indeed, believe about them what you may.