What is papañca?

Papañca means proliferating with ignorance.

For example, SN 22.81 says 'contact' in dependent origination is 'contact with ignorance' ('avijjāsamphassajena').

For example, MN 18 says papanca (arising following contact, feeling & perception) is/results in vexation & suffering.

SN 22.5 says the word 'samudaya' ('arising') means when the mind continues to desire the five aggregates. Therefore, the word 'cessation' means when ignorance, desire & clinging cease.

Suttas such as MN 140 say a Buddha does not die ('marana') because their mind is free from conceiving 'self'.

The 1st noble truth summarizes all suffering as attachment (upadana).

Since MN 18 says papanca is vexation & suffering, papanca must be similar to attachment.

AN 4.174 says the cessation of sense contact is appapanca or non-papanca. AN 4.174 accords with the definition of cessation in SN 22.5, namely, the cessation of ignorance & attachment towards the five aggregates & sense contact.

AN 4.174 may also suggest views about Buddhas & death are papanca. They are certainly papanca because the word 'death' ('marana') does not apply to Buddhas (refer to SN 22.85).

Therefore, papanca appears to mean mental proliferation that produces suffering and is characterized by wrong views.

Papanca appears to not simply mean thinking, conceptualization or differentiating. Papanca appears to refer to ignorant thinking & foolish proliferating.

• The PTS dictionary says it means "obstacle or impediment", and that it maybe isn't related to the Sanskrit prapañca.

• It's used in DN 21 e.g. like this:

  “But how does a mendicant appropriately practice for the cessation of concepts of identity that emerge from the proliferation of perceptions?”
  “Kathaṃ paṭipanno pana, mārisa, bhikkhu papañcasaññāsaṅkhānirodhasāruppagāminiṃ paṭipadaṃ paṭipanno hotī”ti?

  In papañcasaññāsaṅkhānirodhasāruppagāminiṃ perhaps the "proliferation" part of the meaning comes from saṅkhā rather than papañca, and "perception" is from saññā -- therefore papañca by itself only means "impediment" not "conceptual proliferation".

• In MN 18 too it's mostly used in compound words like papañcasaññāsaṅkhā (as in DN 21 above).

• The only other way it's used in MN 18 is in papañceti which Ven Sujato translated as ...

  What you think about, you proliferate.
  yaṃ vitakketi taṃ papañceti

  ... but I don't know how to verify/justify that translation.

• There are not many suttas in which it's used at all: it's not a commonly-used word.

  (That search also returns results like pāpañca i.e. with a long first vowel, but I think that's a different word, which means evil).

  (That search may be unreliable e.g. it didn't find it's being used in Snp 4.11, I don't know why, so maybe by relying on this search as I do in this answer I miss some places where it's used).

• A few suttas use it in the formula "Papañca udapānañca", e.g. SN 1.47, where it's translated as "a drinking place and a well" (I don't know why, so I'll ignore this meaning), ditto in the phrase "Papañca vivane".

• It's used in AN 4.174, in phrases like iti vadaṃ appapañcaṃ papañceti translated as "you’re proliferating the unproliferated". However a) I don't understand the overall meaning of this sutta b) for all I know this might just as well be translated as "you're hindering the unhindered".

• It's used in Thag 17.2 translated as follows ...

  Whoever is devoted to proliferation,
  A wild animal delighting in proliferation,
  Is deprived of nibbāna,
  The unexcelled safety from the yoke.

  Whoever has given up proliferation,
  Delighting in the path free of proliferation,
  Is blessed with nibbāna,
  The unexcelled safety from the yoke.

  ... I dont know why that's translated as (specifically) "proliferation" instead of (more generally) "an unspecified kind of hindrance". The same formula is used in AN 6.14 and AN 6.15.

• It's used in Snp 4.11 whose topic is "Arguments and Disputes". I guess this is a famous use of the word. Here it's used in the phrase Saññānidānā hi papañcasaṅkhā -- note that here again it's used with Saññā and saṅkhā explicitly.

That's about all there is, the only places it's used.

In summary I think that:

• It's rarely used
• It just means "hindrance"

• In the (only) places where it's (famously) used i.e. DN 21 and MN 18, it's used in the compound word papañcasaññāsaṅkhā -- which maybe explains why that's translated as "conceptual proliferation" ... I guess that compound word means literally "the hindrance of numerous perceptions".

• Snp 4.11 uses the similar-but-not-identical phrase ...

  Na saññasaññī na visaññasaññī,
  Nopi asaññī na vibhūtasaññī;
  Evaṃ sametassa vibhoti rūpaṃ,
  Saññānidānā hi papañcasaṅkhā

  That's translated as ...

  Neither one of normal perception nor yet abnormal,
  neither unperceiving no cessation of perception,
  but form ceases for one who (has known) it thus:
  Conceptual proliferation has perception as its cause.

  ... i.e. translating papañca and/or papañcasaṅkhā as "conceptual proliferation" again, even though it's missing the word saññā.

  I guess that literally should be translated as "perceptions cause many troubles" -- except that papañcasaṅkhā should be understood as actually saying (or meaning) papañcasaññāsaṅkhā: IMO it's been abbreviated from papañcasaññāsaṅkhā to fit the meter (because Snp 4.11 is verse, and they do that when it comes to versifying).

• All three (MN 18, DN 21, and Snp 4.11) are describing this as a cause of arguments and quarrels (MN 18 and Snp 4.11), and/or envy and hostility (DN 21).

  That explains this introduction to MN 18:

  This discourse plays a central role in the early Buddhist analysis of conflict. As might be expected, the blame for conflict lies within, in the unskillful habits of the mind, rather than without. The culprit in this case is a habit called papañca.

A good reference on this topic is Bhikkhu Ñāṇananda's 155 pg. book, Concept and Reality in Early Buddhist Thought. It is available online as a free download.

Quoting from the blurb on the back cover:

This work deals primarily with two important, but controversial doctrinal terms, found in the Pali Canon - Papañca and Papañca- saññā-sankhā. The characteristically Buddhistic doctrine of 'not-self' (anattā) is shown in new dimensions of significance having far-reaching implications not only in the context of Buddhism but also for the student of philosophy, psychology and ethics, as well.

I think it probably means "recognizing". Thus we get something like

What one perceives that one thinks about. What one thinks about one recognizes. One's recognition is the starting point from which a person is beset by the proliferating perceptions associated with the theme. This occurs with respect to sights known by the eye in the past, future, and present.

How to analysis this vocabulary?

Pac(a/i) + [ṃ of abbhāsa(root-repeating)] + pac(a/i) + a = papañca (saddanīti dhātumālā).

Pāka/vipāka, which use the same pac(a/i)-root, didn't abbhāsa by Buddha, because it is resultant. It is not the lead-cause dependent-origination-loop's repeating. So, Buddha didn't abbhāsa it.

What does pac(a/i) of papañca mean?

It refers to kilesa-vatta (unwholesome-causes) of the dependent origination which are the causes of the dependent-origination-loop's repeating. Because Kamma-vatta (formation/kamma-becomming) depending on kilesa-vatta (avijjā/taṅhā/upādāna) to cook(pacati) pāka/vipāka (resultants) of the dependent origination (vaṭṭa/paṭiccasamuppāda).

Why Buddha did abbhāsa(root-repeating) to pac(a/i) as papañca?

To refer papañca to kilesa-vatta (unwholesome-causes) of the dependent origination. I described above.

Where are kilesa-vaṭṭa (formation) in dependent origination?

The italic text below of Saṃ. Nidāna. Vibhaṅgasutta are kilesa-vaṭṭa (formation), the bold text are vipāka-vaṭṭa, the regular text are kamma-vaṭṭa:

– Katamo ca, bhikkhave, paṭiccasamuppādo?

– And what, bhikkhus, is paṭicca-samuppāda?

Avijjā·paccayā, bhikkhave, saṅkhārā;

Conditioned by avijjā, bhikkhus, there are saṅkhāras

saṅkhāra·paccayā viññāṇaṃ;

conditioned by saṅkhāras, there is viññāṇa

viññāṇa·paccayā nāmarūpaṃ;

conditioned by viññāṇa, there is nāmarūpa

nāmarūpa·paccayā saḷāyatanaṃ;

conditioned by nāmarūpa, there are saḷāyatanas

saḷāyatana·paccayā phasso;

conditioned by saḷāyatanas, there is phassa

phassa·paccayā vedanā;

conditioned by phassa, there is vedanā

vedanā·paccayā taṇhā;

conditioned by vedanā, there is taṇhā

taṇhā·paccayā upādānaṃ;

conditioned by taṇhā, there is upādāna

upādāna·paccayā bhavo;

conditioned by upādāna, there is bhava

bhava·paccayā jāti;

conditioned by bhava, there is jāti

jāti·paccayā jarā-maraṇaṃ soka parideva dukkha domanass·upāyāsā sambhavanti. Evam·etassa kevalassa dukkha'k'khandhassa samudayo hoti.

conditioned by jāti arise jarā-maraṇa, sorrow, lamentation, dukkha, domanassa and distress. Thus arises this whole mass of dukkha.

Which are the evidence sutta of this answer?

Every sutta which are contented papañca and papañceti are the evidences. They talking about dependent origination (paṭiccasamuppāda). So, I analysis papañca-word as dependent origination follow to those suttas' context.

Why atthakathā comments papañca as the Resistance?

Because the kilesa-vaṭṭa causes the repeating of dependent-origination-loop. So, atthakathā comments papañca as the resistance of the dependent-origination-loop cessation.

Why atthakathā comments papañca as only Taṇhā, Diṭṭhi, and Māna, but the sutta refer to 7 anusaya?

It is just a brief of those 7 anusaya to cover 10 fetters in brief 3 kilesa, some point of atthakathā comment more than 3 as well. So, the sutta and atthakathā similarly explained papañca.

I am not a translator and do not know of the proper translation, but another closely related word that I'm particularly fond of is hypostatize. There is also the noun form hypostatization.

Mark Siderits and Shoryu Katsura translate the Sanskrit version of this term - prapañca - as hypostatization in Nagarjuna's Middle Way so it looks like I'm not too far off :)

The general definition is very close to reification. It means to attribute real ontological identity to a concept and Mirriam Webster gives the root as the Greek hypostatos which is "substantially existing."

Here is my favorite example of hypostatizing...

From Insight Into Emptiness page 258, “For example, a young woman may want to have a child. When she is asleep, she dreams she gives birth to a child and is elated. But later in the dream, the child dies and she is devastated. However, on waking, she sees that neither the exhilarating appearance of having a child that brought her joy nor the horrible appearance of the child’s death that caused her anguish is real.”

Before she woke up she hypostatized her child (attributed real concrete existence to it) and this led to both elation and anguish. After she woke she stopped the hypostatization and the elation and anguish faded. However, there is also something very subtle happening when she woke up: she considered the dream unreal in relation to something else! Unreal and real are a dichotomy and mutually dependent notions :)

Another great and famous example is that of how three different beings perceive a cup filled with a liquid substance.

Three beings each perceive a cup filled with a liquid substance in front of them. The first, a god, looks and takes a sip and perceives, “ambrosia!” The second, a human being, looks and takes a sip and perceives, “water.” The third, a hungry ghost, looks and takes a sip and perceives, “blood and pus.”

Which is real? Which is unreal? What is worthy of being hypostatized and what is not? This is sometimes referred to as the simile of the three cups of liquid in Mahayana texts.

Another famous example by Nagarjuna is the body of a woman being seen differently by an ascetic, a lustful man, or a wild dog:

With respect to the same female body,
Three different notions are entertained
By the ascetic, the lustful and a [wild] dog,
As a corpse, an object of lust, or food.

Each hypostatizes the body as very different things. Which is real? Which is unreal? Can the body be thought of as having any essence whatsoever? Or is each perception thoroughly and utterly relative and dependent? Is there anything whatsoever objectively real or worthy of being hypostatized in such a situation? Can any of it withstand analysis?

In fact, prapañca is a concept so important to Nagarjuna that he opens his famous Fundamental Treatise on the Middle Way with this:

And here is how Siderits characterizes the commentaries on this opening Homage Verse:

Indeed, if you look through the rest of Nagarjuna's verses you will see that this is a major subject of the treatise as the commentaries attest.

Here is that very same Homage Verse as translated by Garfield and commented on by Je Tsongkhapa:

I prostrate to the perfect Buddha,
The best of all teachers, who taught that
That which is dependent origination is
Without cessation, without arising;
Without annihilation, without permanence;
Without coming; without going;
Without distinction, without identity
And peaceful—free from fabrication.

Je Tsongkhapa cites Chandrakirti saying in his Prasannapada that these Homage Verses, "reveal the content and ultimate purpose of the Treatise."

Further, this site gives prapanca in Tibetan as spros pa which is also how it is used in Je Tsongkhapa's Ocean of Reasoning:

free from conceptual and verbal elaboration : sgra rtog gi spros pa zhi ba
sgra rtog gi spros pa zhi ba : free from conceptual and verbal fabrication

First, I will start with a canonical definition of papanca from MN 18 (translated by Ven. Sujato):

Eye consciousness arises dependent on the eye and sights. The meeting of the three is contact. Contact is a condition for feeling. What you feel, you perceive. What you perceive, you think about. What you think about, you proliferate. What you proliferate about is the source from which a person is beset by concepts of identity that emerge from the proliferation of perceptions. This occurs with respect to sights known by the eye in the past, future, and present.
MN 18

And the same applies to the other five senses and their sense objects, including mind and thoughts.

For e.g. I see a cup. Feeling means sensing the vision of the cup with my eyes. Then I perceive it, meaning I identify it as "my late grandmother's cup" from memory. Then I proliferate, meaning I think about the times I spent with my grandmother and the times she drank using the cup. It stirs emotions about my late grandmother. Then I think about what I'm going to do with the cup in future. That's mental proliferation (papanca).

"What is Papañca?" is precisely the name of the article by Andrew Olendzki, the editor of the Insight Journal, who tries to answer this question, and then relates the purpose of vipassana later in his article, beyond my quote below.

Basically, papañca is the layers of thoughts and concepts that obscures what is barely perceived.

Imagine you walk through a canteen line and the canteen staff places five pieces of potato on your plate, while placing six pieces of potato on another person's plate. If you get angry about this, thinking perhaps, that the canteen staff is discriminating against you perhaps due to your ethnicity - well, this is an example of papañca, where it gives rise to aversion. You imagined a lot of stuff, on top of what is insignificant.

Another good example is this answer, where the author wrote that she was terrified because she misinterpreted the nightly sounds of cats mating as an adult woman and her baby crying in pain.

I've recently spoken to a depressed friend who did not feel that he is good enough and suffers from a lack of self-confidence. He cites examples of where others are better than him. I quoted qualities and examples of him that are better than each of those other persons and he was shocked. He never saw it in that way before. He was too obscured in his mental commentaries of his deficiencies that he couldn't see his good qualities and personal strengths.

But papañca can be a lot milder than that. For e.g. your feeling of patriotism or pride towards your country or ethnicity or religion is in my opinion, papañca too, as it a built-up concept.

In the article, he continues to speak of Vipassana as a means of one seeing things as they truly are.

The opposite of "papañca" could be "yathābhūtaṃ pajānāti" which means "seeing things clearly as they truly are".

From Andrew Olendzki's article, "What is Papañca?":

papahcabkirata paja nippapanca tathagata
“People delight in proliferation, the Tathagata in nonproliferation.”
—Dhammapada 254

Papañca is one of those delightful Pali words that rolls off the tongue (or bursts through the lips, in this case) and hits the nail on the head. It points to something so immediate, so pervasive, and so insidious that it deserves to join the English language and enter into common usage. The exact derivation of papañca is not entirely clear, but its sense hovers somewhere between the three nodes of 1) to spread out or proliferate; 2) an illusion or an obsession; and 3) an obstacle or impediment. The place where these three meanings converge in experience is not hard to locate. Sit down with your back straight and your legs folded around your ankles, close your eyes, and attend carefully to your experience. What do you see? Papañca.

This term is used to describe the tendency of the mind to 1) spread out from and elaborate upon any sense object that arises in experience, smothering it with wave after wave of mental elaboration, 2) most of which is illusory, repetitive, and even obsessive, 3) which effectively blocks any sort of mental calm or clarity of mind.

These are the narrative loops that play over and over in the mind, the trains of thought pulling out of the station one after another and taking us for a long ride down the track before we even know we’re aboard. Bhikkhu Bodhi, eloquent as always, calls papañca “the propensity of the worldling’s imagination to erupt in an effusion of mental commentary that obscures the bare data of cognition” (from note 229 in Majjkima Nikaya (MN)).

Also of interest from the Tuvataka Sutta:

Seeing in what way is a monk unbound,
clinging to nothing in the world?"
"He should put an entire stop
to the root of objectification-classifications:
'I am the thinker.'

Ven. Thanissaro's footnote states:

On objectification-classifications and their role in leading to conflict, see Sn 4.11 and the introduction to MN 18. The perception, "I am the thinker" lies at the root of these classifications in that it reads into the immediate present a set of distinctions — I/not-I; being/not-being; thinker/thought; identity/non-identity — that then can proliferate into mental and physical conflict. The conceit inherent in this perception thus forms a fetter on the mind. To become unbound, one must learn to examine these distinctions — which we all take for granted — to see that they are simply assumptions that are not inherent in experience, and that we would be better off to be able to drop them.

That means the mind creates a self and then it objectifies and classifies everything else based on its relationship to the self.

For e.g. to a non-vegetarian, cooked meat looks like delicious food and to a vegan, it's disgusting.

The root of objectification-classification is the mental idea of the self.

The Madhupindika Sutta, cited in the question, seems to state that objectification (papañca) leads to "obsessions of passion, the obsessions of resistance, the obsessions of views, the obsessions of uncertainty, the obsessions of conceit, the obsessions of passion for becoming, & the obsessions of ignorance" and also "taking up rods & bladed weapons, of arguments, quarrels, disputes, accusations, divisive tale-bearing, & false speech".

"If, monk, with regard to the cause whereby the perceptions & categories of objectification assail a person, there is nothing there to relish, welcome, or remain fastened to, then that is the end of the obsessions of passion, the obsessions of resistance, the obsessions of views, the obsessions of uncertainty, the obsessions of conceit, the obsessions of passion for becoming, & the obsessions of ignorance. That is the end of taking up rods & bladed weapons, of arguments, quarrels, disputes, accusations, divisive tale-bearing, & false speech. That is where these evil, unskillful things cease without remainder."