One bhikkhu approached another and asked him: “In what way, friend, is a bhikkhu’s vision well purified?”

“When, friend, a bhikkhu understands as they really are the origin and the passing away of the six bases for contact, in this way his vision is well purified.”

Then the first bhikkhu, dissatisfied with the other’s answer, approached another bhikkhu and asked him: “In what way, friend, is a bhikkhu’s vision well purified?”

“When, friend, a bhikkhu understands as they really are the origin and the passing away of the five aggregates subject to clinging, in this way his vision is well purified.”

Again, the first bhikkhu, dissatisfied with the other’s answer, approached still another bhikkhu and asked him: “In what way, friend, is a bhikkhu’s vision well purified?”

“When, friend, a bhikkhu understands as they really are the origin and the passing away of the four great elements, in this way his vision is well purified.”

Again, the first bhikkhu, dissatisfied with the other’s answer, approached still another bhikkhu and asked him: “In what way, friend, is a bhikkhu’s vision well purified?”

“When, friend, a bhikkhu understands as it really is: ‘Whatever is subject to origination is all subject to cessation,’ in this way his vision is well purified.”

Then the first bhikkhu, dissatisfied with the other’s answer, approached the Blessed One, reported everything that had happened, and asked: “In what way, venerable sir, is a bhikkhu’s vision well purified?”

“Bhikkhu, suppose there was a man who had never before seen a Kiṃ tree. He might approach a man who had seen a Kiṃ tree and ask him: ‘Sir, what is a Kiṃ tree like?’ The other might answer: ‘Good man, a Kiṃ tree is blackish, like a charred stump.’ On that occasion a kiṃsuka tree might have been exactly as that man had seen it.

“Then that man, dissatisfied with the other’s answer, might approach another man who had seen a kiṃsuka tree and ask him: ‘Sir, what is a kiṃsuka tree like?’ The other might answer: ‘Good man, a kiṃsuka tree is reddish, like a piece of meat.’ On that occasion a kiṃsuka tree might have been exactly as that man had seen it.

“Then that man, dissatisfied with the other’s answer, might approach still another man who had seen a kiṃsuka tree and ask him: ’Sir, what is a kiṃsuka tree like?’ The other might answer: ‘Good man, a kiṃsuka tree has strips of bark hanging down and burst pods, like an acacia tree.’ On that occasion a kiṃsuka tree might have been exactly as that man had seen it.

“Then that man, dissatisfied with the other’s answer, might approach still another man who had seen a kiṃsuka tree and ask him: ‘Sir, what is a kiṃsuka tree like?’ The other might answer: ‘Good man, a kiṃsuka tree has plenty of leaves and foliage and gives abundant shade, like a banyan tree.’ On that occasion a kiṃsuka tree might have been exactly as that man had seen it.

“So too, bhikkhu, those superior men answered as they were disposed in just the way their own vision had been well purified. “Suppose, bhikkhu, a king had a frontier city with strong ramparts, walls, and arches, and with six gates. The gatekeeper posted there would be wise, competent, and intelligent; one who keeps out strangers and admits acquaintances. A swift pair of messengers would come from the east and ask the gatekeeper: ‘Where, good man, is the lord of this city?’ He would reply: ‘He is sitting in the central square.’ Then the swift pair of messengers would deliver a message of reality to the lord of the city and leave by the route by which they had arrived. Similarly, messengers would come from the west, from the north, from the south, deliver their message, and leave by the route by which they had arrived.

“I have made up this simile, bhikkhu, in order to convey a meaning. This is the meaning here: ‘The city’: this is a designation for this body consisting of the four great elements, originating from mother and father, built up out of boiled rice and gruel, subject to impermanence, to being worn and rubbed away, to breaking apart and dispersal. ‘The six gates’: this is a designation for the six internal sense bases. ‘The gatekeeper’: this is a designation for mindfulness. ‘The swift pair of messengers’: this is a designation for serenity and insight. ‘The lord of the city’: this is designation for consciousness. ‘The central square’: this is a designation for the four great elements—the earth element, the water element, the heat element, the air element. ‘A message of reality’: this is a designation for Nibbāna. ‘The route by which they had arrived’: this is a designation for the Noble Eightfold Path; that is, right view … right concentration.”