Translating Classical Buddhism to Modern English

The Medium Discourses

Chapter 7: King Dīrghāyu

81. Mindfulness of Body

1. Thus have I heard:[1] One time, the Buddha traveled to the country of Aṅga with a group of great monks. They went to Āpaṇa and stayed at Kaineya’s residence.

Introduction

2. After the night passed and the sun rose, the Bhagavān put on his robe and took his bowl into Āpaṇa to solicit alms. When his meal was finished, he put away his robe and bowl, washed his hands and feet, put his sitting mat over his shoulder, and went into a grove in the afternoon. Going into that grove, he spread out his sitting mat under a tree and sat cross-legged there.

3. At the time, a large group of monks had gathered in the discussion hall after the midday meal, and they were conversing about this topic: “Good men, the Bhagavān is rare and extraordinary. He cultivates mindfulness of body and discerns and disseminates it. His is the highest knowledge, highest observation, highest cultivation, and highest discipline. He has well perfected good conduct and resides in a unified mind. The Buddha teaches that mindfulness of body has great rewards. One attains the vision and eyes to see the supreme truth.”

4. Just then, the Bhagavān was sitting in repose and used the divine ear that transcends that of humans. He heard the monks gathered in the discussion hall after the midday meal conversing about this topic: “Good men, the Bhagavān is rare and extraordinary. He cultivates mindfulness of body and discerns and disseminates it. His is the highest knowledge, highest observation, highest cultivation, and highest discipline. He has well perfected good conduct and resides in a unified mind. The Buddha teaches that mindfulness of body has great rewards. One attains the vision and eyes to see the supreme truth.” After hearing this, the Bhagavān then got up from his repose in the afternoon, went to the discussion hall, prepared his seat in front of the monks, and sat down.

5. It was then that the Bhagavān addressed the monks, “What topic have you been discussing together? What was the reason you gathered here in the discussion hall?”

The monks said, “Bhagavān, we monks gathered here in the discussion hall after the midday meal to discuss this topic: ‘Good men, the Bhagavān is rare and extraordinary. He cultivates mindfulness of body and discerns and disseminates it. His is the highest knowledge, highest observation, highest cultivation, and highest discipline. He has well perfected good conduct and resides in a unified mind. The Buddha teaches that mindfulness of body has great rewards. One attains the vision and eyes to see the supreme truth.’ Bhagavān, we’ve been discussing this topic together. This was the reason we gathered here in the discussion hall.”

6. The Bhagavān again addressed the monks, “How do I teach the cultivation of mindfulness of body, discerning and disseminating it? What great rewards does it attain?”

The monks then said to the Bhagavān, “The Bhagavān is the Dharma root! The Bhagavān is the Dharma lord! The Dharma comes from the Bhagavān! May it please him to discuss it. After hearing it, we’ll get a detailed knowledge of its meaning.”

7. The Buddha then told them, “Listen closely, and well consider it. I will discern its meaning for you.”

The monks then accepted the teaching and listened.

The 18 Practices

8. The Buddha said, “How does a monk cultivate mindfulness of body? That monk walks and knows he’s walking. He stands and knows he’s standing, sits and knows he’s sitting, and lies down and knows he’s lying down. He sleeps and knows he’s sleeping, wakes and knows he’s waking, and he sleeps and wakes and knows he’s slept and woke up.

9. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

10. “Furthermore, a monk cultivates mindfulness of body. That monk correctly knows that he’s exiting and entering, well observes and discerns that he’s bending and stretching high and low. His manner is peaceful, and he wears his outer and other robes and [carries] his bowl well. He’s correctly aware when walking, standing, sitting, lying, sleeping, waking, speaking, and being silent.

11. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

12. “Furthermore, a monk cultivates mindfulness of body. That monk produces mindfulness of what’s bad and unwholesome. He subdues and extinguishes it with mindfulness of what’s good. He’s like a carpenter or a carpenter’s apprentice who ties wood together with a cord and then chops off the excess with a sharp ax to make it straight. Thus, the monk produces mindfulness of what’s bad and unwholesome, and he subdues and extinguishes it with mindfulness of what’s good.

13. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

14. “Furthermore, a monk cultivates mindfulness of body. That monk puts his teeth together, presses his tongue up against his palate, and uses his mind to govern his thoughts, subduing and extinguishing them. It’s like two strong men arresting a weak man. They go from place to place holding, controlling, and disciplining him. Thus, that monk puts his teeth together, presses his tongue against his palate, and uses his mind to govern his thoughts, subduing and extinguishing them.

15. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

16. “Furthermore, a monk cultivates mindfulness of body. That monk is mindful of breathing in and knows he’s mindful of breathing in. He’s mindful of breathing out and knows he’s mindful of breathing out. He breaths in long and knows he’s breathing in long. He breaths out long and knows he’s breathing out long. He breaths in short and knows he’s breathing in short. He breaths out short and knows that he’s breathing out short. He learns to breath in with his whole body and learns to breath out with his whole body. He learns to calm his physical action when breathing in and learns to calm his verbal action when breathing out.

17. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

18. “Furthermore, a monk cultivates mindfulness of body. That monk’s body is wet and moistened by joy and happiness that arises from seclusion. It thoroughly fills what’s in his body. There’s nowhere that joy and happiness that arises from seclusion doesn’t reach. It’s like a bath worker who fills a dish with soap and mixes it with water to make a ball. The water wets and moistens it and thoroughly fills it. There’s nowhere it doesn’t reach. Thus, a monk’s body is wet and moistened by joy and happiness that arises from seclusion. It thoroughly fills what’s in his body. There’s nowhere that joy and happiness that arises from seclusion doesn’t reach.

19. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

20. “Furthermore, a monk cultivates mindfulness of body. That monk’s body is wet and moistened by joy and happiness that arises from concentration. It thoroughly fills what’s in his body. There’s nowhere that joy and happiness that arises from seclusion doesn’t reach. It’s like a mountain spring that fills to overflowing with the purest and clearest water. On all four sides, there’s no way for water to go into it. From the bottom of that spring, the water spontaneously wells up and flows out to wet and moisten the mountain and thoroughly fill it. There’s nowhere it doesn’t reach. Thus, a monk’s body is wet and moistened by the joy and happiness that arises from concentration. It thoroughly fills what’s in his body. There’s nowhere that joy and happiness that arises from concentration doesn’t reach.

21. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

22. “Furthermore, a monk cultivates mindfulness of body. That monk’s body is wet and moistened by happiness that arises from the absence of joy. It thoroughly fills what’s in his body. There’s nowhere that happiness that arises from the absence of rapture doesn’t reach. It’s like the blue lotus and the red and white lotuses, which are born from water and grow in water. At the water’s bottom, their roots, stems, flowers, and leaves are all wet and moistened. They are thoroughly filled, and there’s nowhere the water doesn’t reach. Thus, the monk’s body is wet and moistened by happiness that arises from the absence of joy. It thoroughly fills what’s in his body. There’s nowhere that happiness that arises from the absence of joy doesn’t reach.

23. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

24. “Furthermore, a monk cultivates mindfulness of body. What’s in that monk’s body is filled with the accomplishment of the mental freedom of a pure mind. There’s nowhere in his body that that pure mind doesn’t reach. He’s like a person wearing a seven- or eight-cubit robe. From head to toe, there’s no part of his body that isn’t covered. Thus, what’s in that monk’s body is filled with the accomplishment of the mental freedom of a pure mind. There’s nowhere in his body that that pure mind doesn’t reach.

25. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

26. “Furthermore, a monk cultivates mindfulness of body. That monk is mindful of the perception of light. That mindfulness is well-acquired, well-maintained, and well-intended. As before, it’s likewise afterward. As after, it’s likewise beforehand. As day, it’s likewise at night. As night, it’s likewise during daytime. As below, it’s likewise above. As above, it’s likewise below. Thus, he isn’t mistaken, and his mind has no fetters. He cultivates a radiant mind, and his mind is never covered by darkness.

27. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

28. “Furthermore, a monk cultivates mindfulness of body. That monk observes appearances, and that mindfulness is well-acquired, well-maintained, and well-intended. He’s like a person sitting and observing someone lying down or lying down and observing someone sitting. Thus, the monk observes appearances, and that mindfulness is well-acquired, well-maintained, and well-intended.

29. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

30. “Furthermore, a monk cultivates mindfulness of body. That monk follows this body’s loveliness and ugliness from head to toe according to its abiding. He observes the various ways it’s filled with impurities. That is, in this body there’s beard, hair, nails, teeth, coarse, fine, and thin skin, flesh, tendons, bones, heart, kidneys, liver, lungs, large and small intestines, spleen, stomach, dung, brain and spine, tears, sweat, phlegm, pus, blood, fat, marrow, saliva, bile, and urine. He’s like a man with eyes to look at a container full of various seeds. He discerns them clearly as rice, millet, barley, wheat, large and small sesame, oilseed, and mustard seed. Thus, the monk follows this body’s loveliness and ugliness from head to toe according to its abiding. He observes the various ways it’s filled with impurities. That is, in this body there’s beard, hair, nails, teeth, coarse, fine, and thin skin, flesh, tendons, bones, heart, kidneys, liver, lungs, large and small intestines, spleen, stomach, dung, brain and spine, tears, sweat, phlegm, pus, blood, fat, marrow, saliva, bile, and urine.

31. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

32. “Furthermore, a monk cultivates mindfulness of body. That monk observes the body’s elements: ‘In this body of mine, there’s the element of earth, element of water, element of fire, element of air, element of space, and element of consciousness.’ It’s like a butcher’s son who slaughters a cow, skins it, spreads its hide on the ground, and divides it into six pieces. Thus, the monk observes the elements of his body: ‘In this body of mine, there’s the element of earth, element of water, element of fire, element of air, element of space, and element of consciousness.’

33. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

34. “Furthermore, a monk cultivates mindfulness of body. That monk observes a dead corpse, whether one day or two, six or seven days old. It’s been pecked by crows and kites, eaten by wolves and dogs, burned, or buried in the ground, and it’s thoroughly rotted and decayed. He compares himself to what he’s seen: ‘Now, this body of mine will be likewise. Both have this principle; it’ll never escape this.’

35. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

36. “Furthermore, a monk cultivates mindfulness of body. That monk sees as before a skeleton, bluish, rotted, half-eaten, or just bones on the ground at a charnel ground. He compares himself to what he’s seen: ‘Now, this body of mine will be likewise. Both have this principle; it’ll never escape this.’

37. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

38. “Furthermore, a monk cultivates mindfulness of body. That monk as before sees skin, flesh, and blood removed [from the bones] and only sinews connecting them at a charnel ground. He compares himself to what he’s seen: ‘Now, this body of mine will be likewise. Both have this principle; it’ll never escape this.’

39. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

40. “Furthermore, a monk cultivates mindfulness of body. That monk as before sees bones with sinews removed and scattered in different directions at a charnel ground: Foot bones, shoulder bones, thigh bones, hip bones, back bones, shoulder bones, neck bones, and skull bones. Each lies in a different place. He compares himself to what he’s seen: ‘Now, this body of mine will be likewise. Both have this principle; it’ll never escape this.’

41. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

42. “Furthermore, a monk cultivates mindfulness of body. That monk as before sees bones at a charnel ground as white as seashells, blue like a pigeon, or red like smeared blood, and they’re decayed, broken, and reduced to dust. He compares himself to what he’s seen: ‘Now, this body of mine will be likewise. Both have this principle; it’ll never escape this.’

43. “Thus, a monk follows his physical actions, knowing the above as it truly is. If he thus goes into seclusion and lives alone, his thoughts aren’t careless. He cultivates diligence, stops mental disturbances, and attains a concentrated state of mind. After attaining a concentrated state of mind, he then knows the above as it truly is. This is called a monk who cultivates mindfulness of body.

Analogies about Correctly Cultivating Mindfulness of Body

44. “If someone thus cultivates mindfulness of body and thus disseminates it, good qualities will be fully present in them, which are the factors of the path. If their mind is filled with mental freedom, it’s like the ocean in which all the small streams are present. If someone thus cultivates mindfulness of body and thus disseminates it, good qualities will be fully present in them, which are the factors of the path.

45. “If there’s an ascetic or priest who doesn’t correctly establish mindfulness of body and travels around will little thought, then Māra Pāpīyān can surely get an advantage over them. Why is that? It’s because that ascetic or priest is empty and lacks mindfulness of body. They’re like a clay pot that’s empty and lacks water when it’s correctly placed [upright] on the ground. If someone were to bring water and pour it into the pot, what do you monks think? Will that pot thus accept the water?” The monks answered, “It would accept it, Bhagavān. Why is that? It’s empty and lacks water, and it’s correctly placed [upright] on the ground. It therefore will surely accept it.”

46. “Thus, if an ascetic or priest doesn’t correctly establish mindfulness of body and travels around with little thought, Māra Pāpīyān can surely get an advantage over them. Why is that? That ascetic or priest is empty and lacking mindfulness of body.

47. “If an ascetic or priest correctly establishes mindfulness of body and travels around with measureless thought, then Māra Pāpīyān will never get an advantage over them. Why is that? That ascetic or priest isn’t empty and has mindfulness of body. They’re like a clay pot that’s full of water and correctly placed [upright] on the ground. If someone were to bring water and pour it into the clay pot, what do you monks think? Would that clay pot accept more water?”

The monks answered, “No, Bhagavān. Why is that? The pot is full of water and correctly placed [upright] on the ground. It therefore won’t accept it.”

48. “Thus, if an ascetic or priest correctly establishes mindfulness of body and travels around with measureless thought, then Māra Pāpīyān will never get an advantage over them. Why is that? That ascetic or priest isn’t empty and has mindfulness of body.

49. “If an ascetic or priest doesn’t correctly establish mindfulness of body and travels around with little thought, then Māra Pāpīyān can surely get an advantage over them. Why is that? That ascetic or priest is empty and lacks mindfulness of body. He’s like a strong man who throws a huge, heavy stone into a mudhole. Monks, what do you think? Would the mud accept it?”

The monks answered, “It would accept it, Bhagavān. Why is that? A heavy stone sinks in mud. It therefore would accept it.”

50. “Thus, if an ascetic or priest doesn’t correctly establish mindfulness of body and travels around with little thought, then Māra Pāpīyān can surely get an advantage over them. Why is that? That ascetic or priest is empty and lacks mindfulness of body.

51. “If an ascetic or priest correctly establishes mindfulness of body and travels around with measureless thought, then Māra Pāpīyān will never get an advantage over them. Why is that? That ascetic or priest isn’t empty and has mindfulness of body. He’s like a strong man tossing a small ball against a level door. Monks, what do you think? Would it enter the door?”

The monks answered, “No, Bhagavān. Why is that? A small ball bounces off a door that’s level standing. It therefore won’t enter it.”

52. “Thus, if an ascetic or priest correctly establishes mindfulness of body and travels around with measureless thought, then Māra Pāpīyān will never get an advantage over him. Why is that? That ascetic or priest isn’t empty and has mindfulness of body.

53. “If an ascetic or priest doesn’t correctly establish mindfulness of body and travels around with little thought, then Māra Pāpīyān can surely get an advantage over them. Why is that? That ascetic or priest is empty and lacks mindfulness of body. He’s like someone seeking fire considers dry wood to be its mother and rubs a dry stick into it. Monks, what do you think? Would that person thus obtain fire?”

The monks replied, “They would obtain it, Bhagavān. Why is that? By rubbing a dry stick into dry wood, they’ll surely obtain it.”

54. “Thus, if an ascetic or priest doesn’t correctly establish mindfulness of body and travels around with little thought, then Māra Pāpīyān can surely get an advantage over them. Why is that? That ascetic or priest is empty and lacks mindfulness of body.

55. “If an ascetic or priest correctly establishes mindfulness of body and travels around with measureless thought, then Māra Pāpīyān will never get an advantage over them. Why is that? That ascetic or priest isn’t empty and has mindfulness of body. He’s like someone seeking fire who considers wet wood to be its mother and rubs a wet stick into it. Monks, what do you think? Would that person thus obtain fire?”

The monks answered, “No, Bhagavān. Why is that? By rubbing a wet stick into wet wood, they won’t obtain it.”

56. “Thus, if an ascetic or priest correctly establishes mindfulness of body and travels around with measureless thought, then Māra Pāpīyān will never get an advantage over them. Why is that? That ascetic or priest isn’t empty and has mindfulness of body.

The 18 Virtues of Cultivating Mindfulness of Body

57. “Someone who thus cultivates mindfulness of body and thus disseminates it should be known to have 18 virtues. What are the 18? That monk can endure hunger, thirst, cold, heat, biting insects, stinging insects, the oppression of sun and wind, and terrible noises. He can also endure being hit with clubs. When he experiences ailments and extreme pain, such that his life is about to end, he’s able to tolerate these discomforts. This is the first virtue of someone who thus cultivates mindfulness of body and thus disseminates it.

58. “Furthermore, that monk tolerates unhappiness. If he becomes unhappy, his mind never attaches to it. This is the second virtue of someone who thus cultivates mindfulness of body and thus disseminates it.

59. “Furthermore, that monk tolerates fear. If he becomes frightened, his mind never attaches to it. This is the third virtue of someone who thus cultivates mindfulness of body and thus disseminates it.

60. “Furthermore, a monk produces the three bad thoughts, which are thoughts of desire, thoughts of anger, and thoughts of harmfulness. If these three bad thoughts arise, his mind never attaches to them. This is the fourth virtue of someone who thus cultivates mindfulness of body and thus disseminates it.

61. “Furthermore, that monk parts with desire and parts with bad and unwholesome things … and attains the accomplishment of the fourth meditation. This is the fifth … eighth virtue of someone who thus cultivates mindfulness of body and thus disseminates it.

62. “Furthermore, once he has ended the three bonds, that monk becomes a stream entrant and doesn’t fall into bad states. He’s certainly destined for right awakening and will experience at most seven existences. After seven rebirths up in heaven or among humans, he’ll reach the limit of suffering. This is the ninth virtue of someone who thus cultivates mindfulness of body and thus disseminates it.

63. “Furthermore, once he ends the three bonds, and lust, hate, and delusion are weakened, that monk attains one rebirth up in heaven or among humans. After one rebirth, he will then reach the limit of suffering. This is the tenth virtue of someone who thus cultivates mindfulness of body and thus disseminates it.

64. “Furthermore, that monk ends the five lower bonds. He’ll be born elsewhere and then [enter] parinirvāṇa. He attains irreversibility and doesn’t return to this world. This is the eleventh virtue of someone who thus cultivates mindfulness of body and thus disseminates it.

65. “Furthermore, if he has calm liberation, that monk parts with form and attains formlessness. According to that manner of concentration, he personally accomplishes its realization. He observes and knows the contaminants and ends the contaminants with wisdom. This is the twelfth virtue of someone who thus cultivates mindfulness of body and thus disseminates it.

66. “Furthermore, that monk [attains] supernormal abilities … the divine ear … knowledge of other minds … knowledge of past lives … knowledge of birth-and-death … has ended the contaminants. Attaining the absence of contaminants, his mind is liberated, and his wisdom is liberated. In the present life, he knows and recognizes for himself the accomplishment of self-realization: ‘Birth has been ended, the religious practice has been established, and the task has been accomplished.’ He is no longer subject to existence and knows is as it really is. This should be known as the thirteenth … eighteenth virtue of someone who thus cultivates mindfulness of body and thus disseminates it.”

67. The Buddha spoke thus. Those monks who heard what the Buddha taught rejoiced and approved.

Notes

  1. Parallels include MN 119. [Back]

Translator: Charles Patton

Last Revised: 14 September 2020