"Life is continually in flux, a stream of phenomena arising and passing away. Like suffering and non-self, impermanence is one of the three marks of existence revealed to the Buddha on the night of his enlightenment. He pointed out the pain and disappointment we inevitably experience if we cling to what can't last. Only nirvana — the unconditioned — escapes the inexorability of time. Impermanence isn't all bad, however. Without change, there would be no life, no growth, no opportunity for spiritual awakening."

"Impermanence seems to be central to your teachings. Why is it such a big deal?

"Impermanence, or anicca in Pali, is one of the three basic characteristics of samsara — the world as we know it. It's intimately entwined with the other two characteristics: dukkha, the truth of suffering, and anatta, or non-self — the truth that phenomena have no intrinsic, enduring substance. Impermanence tells us that people and objects are inconstant and transitory, that thoughts and feelings are as ephemeral as foam atop a wave. Though impermanence is a reality — a natural law — we strongly resist it, for change leads to the pain and disappointment of loss. The most difficult change we face is the ultimate inescapable loss — death.

"But we all know death is inevitable, don't we?

"Knowing the truth and accepting it are very different things. A classic example is the story of Kisa Gotami, who could not accept that her young son had died. Clutching his lifeless body, she went from neighbor to neighbor, begging for medicine to cure him. One man took pity on her and said, 'I don't have the medicine you need, but I know someone who does.' When she came to me demanding the remedy, I sent her off to collect a mustard seed from every house in which no one had died. Empty-handed after a long search, she realized that death is universal, and was finally able to accept her loss. At the same time, she learned that there's a path to the deathless — to nirvana — for those who let go of their attachment to life.

"Are you suggesting that liberation is possible only for those who stop caring about anything?

"Letting go of attachment to life doesn't mean not caring. It means understanding that the pain of everyday experience comes from denying the truth of impermanence. When we fail to accept it, we get caught up in the vicissitudes of life, the 'eight worldly conditions' — gain and loss, fame and disrepute, praise and blame, pleasure and pain — and are at the mercy of our likes and dislikes. Accepting that life is transitory lets you ease your grip on it. When you're not desperately clinging to something, you're free to care for it in a relaxed and loving way.

"But if change and loss are inevitable, doesn't that make life pretty futile?

"Change isn't always negative. It's the very essence of life — it's vital to growth. Without change, existence would indeed be futile: there could be no righting of wrongs, no learning, no possibility of spiritual awakening. Just as what we like inevitably changes or leaves, so too what we don't like passes. Just observe your mind at work, and you'll see this. Thoughts and feelings change constantly.

"But if everything is inconstant and unreliable, what basis is there for caring? It's pretty hard to care for anything without forming some sort of attachment to it.

"As you become aware that nothing lasts forever, you can deepen your appreciation for things as they are now, and not pin your hopes on what may or may not happen in the future."