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During my first weeks with my teacher, Ajaan Fuang, I began to realize that he had psychic powers. He never made a show of them, but I gradually sensed that he could read my mind and anticipate future events. I became intrigued: What else did he know? How did he know it? He must have detected where my thoughts were going, for one evening he gently headed me off: "You know," he said, "the whole aim of our practice is purity of heart. Everything else is just games."
That one phrase — purity of heart — more than intrigued me. It reverberated deep down inside. Although I was extremely disillusioned with Christianity, I still valued Kierkegaard's dictum: Purity of heart is to will one thing. I didn't agree with Kierkegaard as to what that "one thing" was, but I did agree that purity of heart is the most important treasure of life. And here Ajaan Fuang was offering to teach me how to develop it. That's one of the reasons why I stayed with him until he died.
His basic definition of purity of heart was simple enough: a happiness that will never harm anyone. But a happiness like that is hard to find, for ordinary happiness requires that we eat. As the first of the Novice's Questions says: "What is one? All beings subsist on food." This is how the Buddha introduced the topic of causality to young people: The primary causal relationship isn't something gentle like light reflecting off mirrors, or jewels illuminating jewels. It's feeding. Our bodies need physical food for their well-being. Our minds need the food of pleasant sensory contacts, intentions, and consciousness itself in order to function. If you ever want proof that interconnectedness isn't always something to celebrate, just contemplate how the beings of the world feed on one another, physically and emotionally. Interbeing is inter-eating. As Ajaan Suwat, my second teacher once said, "If there were a god who could arrange that by my eating I could make everyone in the world full, I'd bow down to that god." But that's not how eating works.
Ordinarily, even well-intentioned people may not see eating as harmful. We're so compelled to eat that we blind ourselves to its larger impact. Our first pleasure, after the terror of being born, was getting to feed. We did it with our eyes closed, and most people keep their eyes closed to the impact of their feeding throughout life.
But when you go to a quiet, secluded place and start examining your life, you begin to see what an enormous issue it is just to keep the body and mind well fed. On the one hand, you see the suffering you create for others simply in your need to feed. On the other, you see something even more dismaying: the emotions that arise within you when you don't feel that your body and mind are getting enough to eat. You realize that as long as your source of physical or mental food is unreliable, you're unreliable, too. You see why even good people can reach a point where they're capable of murder, deceit, adultery, or theft. Being born with a body means that we're born with a huge bundle of needs that compels and can overwhelm our minds.
Fortunately, we human beings have the potential to civilize our eating habits by learning to wean ourselves from our passion for the junk food of sights, sounds, smells, etc., and look instead for good food within. When we learn to appreciate the joy that comes from generosity, honor, compassion, and trust, we see that it's much more fulfilling than the pleasure that comes simply from grabbing what we can for ourselves. We realize that our happiness can't be independent of the happiness of others. We can give one another our belongings, our time, our love, our selves, and see it not as a loss but as a mutual gain.
Unfortunately, these qualities of the heart are conditional, for they depend on a tender web of beliefs and feelings — belief in justice and the basic goodness of human nature, feelings of trust and affection. When that web breaks, as it so easily can, the heart can turn vicious. We see this in divorce, broken families, and society at large. When the security of our food source — the basis of our mental and material well-being — gets threatened, the finer qualities of the mind can vanish. People who believe in kindness can suddenly seek revenge. Those who espouse non-violence can suddenly call for war. And those who rule by divisiveness — by making a mockery of compassion, prudence, and our common humanity — find a willing following for their law-of-the-jungle agenda.
This is why compassion based only on belief or feeling is not enough to guarantee our behavior — and why the practice of training the mind to reach an unconditioned happiness is not a selfish thing. If you value compassion and trust, it's an imperative, for only an unconditioned happiness can guarantee the purity of your behavior. Independent of space and time, it's beyond alteration. No one can threaten its food source, for it has no need to feed. When you've had even just a glimpse of this happiness, your belief in goodness becomes unshakable. That way other people can totally trust you, and you can genuinely trust yourself. You lack for nothing.
Purity of heart is to know this one thing.