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In one of the most famous similes in the canon, the Buddha compares a spiritual seeker working with their mind to a goldsmith working with gold.
Gold ore has obvious impurities: clumps of sand, gravel, and dirt. The washer places the gold in a tub and washes it again and again until he has washed all the impurities away. But there still remains sand and grit. Again he washes the gold ore until the sand and grit are gone. Even still there is fine sand and dust. Again and again he washes the gold until it is clean.
All that remains is gold dust. Then the goldsmith puts it in the crucible to melt it. Whenever impurities bubble up, he blows them away. Over and over he blows away this dross until it is malleable and glowing. Until he has blown away all the dross, it is still brittle and hard to work. Finally, it is ready to be made into a belt, earring, necklace, or chain.
In the same way, a new spiritual seeker starts with obvious problems: mistakes in behavior, speech, or thought. A new spiritual seeker that is conscientious by nature will learn to abandon these kinds of mistakes.
When he is free from these obvious impurities, there are the more subtle issues like thoughts of desire, thoughts of anger, thoughts of aggression. Again he works to abandon this kind of thinking.
Again he looks at even more subtle issues such as thoughts of social position, thoughts of his hometown, thoughts of reputation. Again he works to abandon this kind of thinking.
All that is left, then, are thoughts about the Dhamma. However, his mind is not yet calm or concentration. He has not yet achieved deep meditation. He is only able to concentrate with great effort. But after a time, he achieves all of these things. He meditation is calm, developed, and deep, and he can sustain it with little effort.
If he chooses, he can then turn his mind toward the higher knowledges, to see for himself what is possible.
If he chooses, he can develop superpowers. He can make copies of himself using his mind and delete those copies whenever he chooses. He can appear and disappear. He can walk through walls or mountains as though they were empty space. He can dive into the earth and swim as though it were water. He can walk on water as though it were dry land. Sitting cross-legged he flies through the air like a bird. He can touch the moon and sun with his hand. He can go to the Brahma heavens.
He could develop the Divine Ear. With this power he can hear any sound on earth or in heaven, no matter how far away.
He could develop the ability to read other’s minds. He knows when someone’s mind is full of desire, anger, or delusion. He knows when someone’s mind is constricted or scattered. He knows when someone’s mind is small or large, developed or undeveloped, concentrated or unconcentrated, liberated or enslaved. He can see this directly for himself.
He could remember all of his paths lives. Thousands of past lives. Many eons of world contraction and expansion. He remembers his name, family, appearance, and support. He remembers his pleasures and his miseries. He remembers his own death and rebirth.
He could remember the past lives of other people. He sees directly how they are reborn according to their past actions: powerful or weak, beautiful or ugly, lucky or unfortunate. These people who behaved unethically in body, speech, or mind; insulting wise people; having wrong views of the world and acting accordingly are reborn in a terrible situation, even into hell. But people who act ethically in body, speech, and mind; don’t insult wise people; having right views and acting accordingly are reborn in a good situation, even heaven. This is the Divine Eye.
He could indeed end all of the corruptions of the mind and be free and liberated right here and now.
-Paṃsudhovaka Sutta AN 3.102 (A i 256)