"We see and distinguish the materials of nature because we see them change. We ourselves change. Over and over we are born and grow and perish. Deep within the hypothalamic nuclei of our brains, our biological clocks oscillate in circadian rhythms. Because we are time-bound creatures with an awareness of our “changing face,” as Yeats writes, we are naturally also driven or tantalized to imagine ourselves outside of time. A central facet of our survival instinct seems to depend on our reluctance to accept our mortality. We fantasize about time stopped, time eliminated; we sing about the inexorable turned as if by magic into the contingent. If we can halt time, as John Donne sings, then 'death shall be no more.´."