What is the importance of the Holy Grail in the book, Thou Art That?

The quest for the Holy Grail, a key component in the Arthurian legends, is mentioned often by Joseph Campbell as an illustration of how Westerners seek to learn things on their own. Whereas in the East, yogis take spiritual responsibility for guiding their charges, in the Western legends, Sir Gawain suggests that the knights swear an oath to proceed into the dense forest individually, avoiding established trails. The quest for the grail satisfies a need to participate in religion subjectively and heroically, not just depending on the objective presence of the gifts in the Mass to save them.