I believe that the essence of human existence is summarized by the Greek story of Damocles. Damocles is a servant of a rich, but cruel tyrant named Dionysus. Damocles tells Dionysus that he envies his station, his food, his life. Dionysus offers a trade. Damocles enjoys the food, the wine, the comfort, and then notices a sharp sword suspended over his head, suspended by a single horsehair. Realizing that something so thin and fragile is the only thing preserving him, Damocles cannot enjoy the food, wine, or comfort. This story is, in fact, what human life is. We enjoy and jubilate but if we ever have occasion to look up and see that the sword is over us, we will be striken with, to borrow from Kierkergaard, fear and trembling. I think it would be awesome if a series of Buddhist commentators were to coment on the story of Damocles and thus highlight some of the essential differences between the Western conception of spirituality (points of terminus) versus the Eastern conception of spirituality (points of change). Imagine if Damocles had said: "The sword may fall but it cannot hit your servant" - that would be very Zen koan.