Even inanimate objects that appear solid and persistent are revealed by modern physics to be in a constant state of flux. An iron bar is mostly empty space, and even the ostensibly solid, sub-atomic particles occupying that space are either moving so rapidly as to be unimaginable or, alternately, exist as clouds of probability rather than as stationary monuments to permanence.
With living things, the world is even less fixed. As Yeats observed: “O body swayed to music, O brightening glance / How can we know the dancer from the dance?” Biologists as well as Buddhists know that living stuff is always dancing, constantly replenished by, and created from, nonliving components. At every moment, our existence takes place only on the instantaneous, knife-edge of Now, which can never be captured and held immobile.
The story goes that as a young man, the Buddha sought to overcome the imperfections of the real world—sickness, old age, and death—by following the path of traditional Hindu asceticism, mortifying the flesh and nearly starving himself. His eventual enlightenment, however, is said to have involved recognition that all things are temporary, ever-changing, and impermanent. Unlike Christ, who promises eternal life, the last words of the Buddha reportedly began, “Decay is inherent in all things.”