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In what ways are the Advaita concept of 'Nirguna Brahman' and the Buddhist concept of Buddha Nature similar and different?
In what ways are the Advaita concept of 'Nirguna Brahman' similar, and/or different, to the Buddhist concept of Buddha Nature?
This is a good comparison, that is where the doubt arose:
Nonduality in Buddhism and Advaita Vedanta
Maybe there is a similarity...?

The article you referenced doesn't mention "Buddha Nature".

And the Gelug presentation (the only one I read so far) is not accurate.

One short paper that compares and contrasts Vedanta and Buddhism is Acharya Mahayogi Sridhar Rana Rinpoche's essay "Madhyamika Buddhism vis-à-vis Hindu Vedanta".

When we compare the Advaita Vedanta, especially as interpreted by Shankara and Madhyamika, whether be it the Svatantric from of Bhabya or Prasangic form of Candrakirti, the sharing of the same language, culture and analogies while talking about two different paradigms becomes obvious. Because of the use of the same language structure (be it Pali or Sanskrit) and the same analogies to express two different paradigms many Vedantins or scholars of Buddhism with Vedantic backgrounds have been fooled into thinking Buddhist Madhyamika is a re-interpretation of Hindu Vedanta.
In fact, the Buddha, after long years of Brahmanic as well as Sramanic meditation, found the concept of Brahma (an ultimately real, unchanging, eternal substratum to this ephemeral transient world) not only inadequate to solve the basic issue of humanity- i. e. sorrow (dukha) and questioned the very existence of such an eternal substratum; but also declared that a search for such an imagined (Skt. Parikalpita Atman) Brahman was a form of escapism and therefore not really spiritual [...]

[...]

Since the concept of Brahman, the truly existent (Skt. paramartha sat) is the very foundation of Hinduism (as a matter of fact some form of an eternal ultimate reality whether it is called God or Nature is the basis of all other religious systems); when Buddhism denies such an ultimate reality (Skt. paramartha satta) in any form, it cuts at the very jugular veins of Hinduism.

[...]

Many Hindu scholars believe that without an ultimate eternal reality then there can be no liberation from the changing, transient samsara; therefore even though the Buddha denied the ultimate reality, he could have meant only conceptually really existing reality, no the eternal ultimate reality which is beyond concepts. Otherwise there cannot be liberation. The fault with this kind of thinking is that it is measuring the thesis (which is no thesis) of the Buddha (or interpreting the Buddha) from within the Hindu paradigm. Remaining within the Hindu paradigm, an eternal ultimate reality is a necessity (a necessary dead end as the Buddha saw it) for the soteriological purpose, i. e. for liberation. Since according to the Buddha there is no Brahman- such a concept being merely an acquired fabrication (skt: parikalpana) learned from wrong (skt: mithya) scriptures, hankering after, searching for such a Brahman is necessary a dead end which leads nowhere, let alone liberation. The Buddhist paradigm if understood correctly, does not require an eternal something or other for liberation. In Buddhism liberation is not realizing such a ground but rather a letting go of all grounds, i. e. realizing groundless.

[...]

But even though Sankara copied the use of these words from Buddhism and also copied many other conceptual words from Nagarjuna to elucidate his Vedantic paradigm, the paradigm that he tries to clarify with these words different. [...] In the Vedantic context, the relative truth (Skt. samvritti satya) is that this samsara is an illusion and the ultimate truth (skt. paramartha satya) is that there is an ultimately existing thing (skt. paramartha satta) transcending/ immanent in this world. The relative truth will vanish like a mist and the both transcendent and immanent Brahman will appear as the only Truth, the world being false. To sum it up, the Vedantic ultimate truth is the existence of an ultimate existence or ultimate reality. Reality here is used as something which exists (skt. satta). However, the Buddhist ultimate truth is the absence of any such satta i. e. ultimately existing thing or ultimate reality.

I think what Buddhism teaches is entirely different in this context. I will resort to logic to answer some of your questions.
Below I question the understanding of Nirguna Brahman:

Shankara asserts that each observer consciousness is identical with
  nirguna brahman (brahman without qualities), and that with liberation,
  the inner physical organ associated with that observer consciousness
  returns to maya-illusion, and that the observer consciousness merges
  with brahman without qualities.

If nirguna brahman is without qualities then how is it known ? It can not be known.
Secondly, if nirguna brahman is an eternal,permanent entity and everybody merges with it then why do karma ? One can kill himself right now and achieve the nirguna brahman. But that doesnt happen. Clearly your nirguna brahman (brahman without qualities) demands qualities in order to merge!! But being himself nirguna(without qualities) how can it demand saguna(good qualities) ?
Thirdly , observer consciousness which merges with the nirguna brahman can not be you or me. Buddha says self is not worth identifying as observer or the participant.In short Observer consciousness which gets liberated is not you or me or anyone because there is no self which is permanent and unchanging.
To answer your question

In what ways are the Advaita concept of 'Nirguna Brahman' similar,
  and/or different, to the Buddhist concept of Buddha Nature?

Nirguna Brahman and Nature of Tathagata can not be compared. Nirguna Brahman is said to exist. Tathagata is not said to be existing or non-existing.

You didn't understand Advaita Vedanta at all.  All these questions are already answered. - If nirguna brahman is without qualities then how is it known ? It can not be known.
Secondly, if nirguna brahman is an eternal,permanent entity and everybody merges with it then why do karma ? One can kill himself right now and achieve the nirguna brahman. But that doesnt happen. Clearly your nirguna brahman (brahman without qualities) demands qualities in order to merge!! But being himself nirguna(without qualities) how can it demand saguna(good qualities) ?

@Rohith Your answers are akin to Münchhausen trilemma... in case you argue of existance of something you should be able to provide a scientific validation.

Buddha Nature is known as "tathagatagarbha".
According to this article:

Tathagatagarbha, or Tathagata-garbha, means "womb" (garbha) of Buddha
  (Tathagata). This refers to a Mahayana Buddhist doctrine that Buddha
  Nature is within all beings. Because this is so, all beings may
  realize enlightenment. Tathagatagarbha often is described as a seed,
  embryo or potentiality within each individual to be developed.

And according to this article:

The 'tathagatagarbha' symbolizes the potential for enlightenment (a
  principle) rather than a material "essence" of ultimate truth.

Buddha Nature is said to originate from the concept of the "luminous mind" in Pabhassara Sutta, which is anyway not eternal, not unconditioned and not impermanent (see this answer).
Nirguna Brahman is described in Advaita as the substratum of all phenomena in Vivekachudamani 289 and as the material cause of the phenomenal universe in Aparokshanubhuti 45.
So, while Buddha Nature is simply the potential for enlightenment (a principle), it is not the material "essence" of ultimate truth, which Nirguna Brahman is. So Buddha Nature and Nirguna Brahman are not the same.
The second concept often wrongly equated with Nirguna Brahman, is Madhyamaka's "emptiness of emptiness" or shunyata. This answer in Hinduism.SE explains why both are not the same. Basically, Nirguna Brahman is empty of qualities but not empty of substance. Meanwhile, shunyata is empty of substance and even this emptiness itself is empty of substance or existence. In other words, Nirguna Brahman is a Transcendental Absolute Reality, while shunyata is devoid of any transcendental or absolute reality.
This is supported by Banaras Hindu University Professor T. R. V. Murti's statement (quoted below) in this book chapter: Murti T.R.V. (1973) Saṁvṛti and Paramārtha in Mādhyamika and Advaita Vedānta. In: Sprung M. (eds) The Problem of Two Truths in Buddhism and Vedānta. Springer, Dordrecht:

It has been the fashion to consider that the differences between the
  Madhyamika śūnyatā and Brahman are rather superficial and even verbal,
  and that the two systems of philosophy are almost identical. At least
  Professor Radhakrishnan thinks so, and Stcherbatsky's and Dasgupta's
  views are not very different. I hold a contrary view altogether: that
  in spite of superficial similarities in form and terminology, the
  differences between them are deep and pervasive.

The third concept usually mistaken for Brahman is the concept of the Eternal Buddha. This comes from the notion that the Buddha's dharmakaya or Dharma Body is Eternal. This does not mean that the Buddha is an eternal being or entity. Rather, it means that the Buddha's teachings (called the Dharma or Dhamma) is eternal. This originates from the Vakkali Sutta where the Buddha told Vakkali:

"Enough, Vakkali! What is there to see in this vile body? He who sees
  Dhamma, Vakkali, sees me; he who sees me sees Dhamma. Truly seeing
  Dhamma, one sees me; seeing me one sees Dhamma."

And also from the Mahaparinibbana Sutta:

Then the Blessed One said to Ven. Ananda, "Now, if it occurs to any of
  you — 'The teaching has lost its authority; we are without a Teacher'
  — do not view it in that way. Whatever Dhamma & Vinaya I have pointed
  out & formulated for you, that will be your Teacher when I am gone.

All Vedanta schools accept that Atman is eternal (according to Bhagavad Gita 2.20), and Brahman is absolute and eternal.
Meanwhile, the anatman or anatta teaching subscribed by all schools of Buddhism, states that there is no eternal self (i.e. no permanent standalone eternal entity) in all phenomena.
The eminent German indologist Professor Helmuth von Glasenapp explains aptly in his essay "Vedanta and Buddhism: A Comparative Study":

Nothing shows better the great distance that separates the Vedanta and
  the teachings of the Buddha, than the fact that the two principal
  concepts of Upanishadic wisdom, Atman and Brahman, do not appear
  anywhere in the Buddhist texts, with the clear and distinct meaning of
  a "primordial ground of the world, core of existence, ens realissimum
  (true substance)," or similarly.

For more discussion on the differences between doctrines in Hinduism and Buddhism, please see this answer.

With respect to the Advaita Vedanta, I assume your question relate to the idea that "All is one, one is all" which expresses non-duality (hence the tag 'nonduality'). From there, I assume you have in mind that the Advaita Vedanta posit this 'oneness' (or one primordial ground of which varieties are a manifestation) as something akin to Buddha Nature.
If it is what you have in mind, that is not Buddhist, and it is not what Buddhist have in mind when they speak of Buddha Nature. In addition, the Buddhist conception of non-duality is different.
From the Madhyamika perspective, for instance, there are three types of dualistic appearances:

The appearance of conventionalities
Appearance of inherent existence
Appearance of apprehending subject and apprehended object as being two different substances

Now, while Madhyamika posit that apprehended object and apprehending consciousness are different substances, Cittamatra assert that apprehended object and apprehending consciousness are the same substance. According to Cittamatra tenets, the apprehended object and the apprehending consciousness both arise simultaneously from a seed that lies in the mind-basis-of-all (alaya vijnana). The mind-basis-of-all being a type of consciousness (the 8th) that is neutral and acts as a repository, and is the object-possessor of the seeds that are "deposited" in it.
Even from this perspective, there isn't anything like a notion of "oneness" similar to that of some Hindu systems. Especially, even in the case where phenomena are not established externally (to consciousness), persons are different from each other and do not emanate from a common ground.
As to Buddha Nature, without going in the details, Karl Brunnholzl gives a decent list of what it is taken to be in different scriptures. It is in  'When the Clouds Part: The Uttaratantra and Its Meditative Tradition as a Bridge between Sutra and Tantra'.

Different Ways of Explaining the Meaning of Tathagatagarbha:

Tathagatagarbha as emptiness
Tathagatagarbha as Minds Luminous Nature
Tathagatagarbha as the Alaya-Consciousness
Tathagatagarbha as a Sentient Being
Tathagatagarbha as the Dharmakàya, Suchness, the Disposition, and Nonconceptuality

Generally speaking, Buddha Nature teachings are part of the Third Turning of the Wheel of Dharma and thus require the wisdom realizing emptiness described in the Second Turning of the Wheel of Dharma to interpret correctly. In this regard, I don't think they can be equated in any way with Vedanta. See here for more on how to regard the provisional and definitive meanings of the Three Turnings of the Wheel of Dharma.

While it is correct that the Third Turning of the Wheel is a clarification of the second and first, it has more to do with the interpretive and definitive nature of the teachings as you mention. But the third turning focuses on the cittamatra school of tenets and hence the interpretations could be closer to Advaita than the true Madhyamika interpretation of the second turning, hence the doubt...

The Third Turning is not a clarification of the Second. The Second Turning is definitive and needs no clarification to one who has realized it. It is the Third Turning which is provisional, not the Second.

Also, I don’t know much about Advaita, but this article says that Advaita “borrowed” some of the concepts, words, and reasoning and “retrofitted” it upon existing religious dogma. At least that seems to be the thesis of this article: https://en.m.wikipedia.org/wiki/Buddhist_influences_on_Advaita_Vedanta

I know the second turning is definitive. When I said clarification, it was with regards to the intent of the Buddha when turning both the first and second wheels. In any case, you could be right, it is the borrowed terminologies that make this difficult to compare. Moreover, I've seen so many interpretations of Advaita, it is really difficult to gain an authoritarian commentary...


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English translation of Vipallāsakathā
I need English translation of Pali sutta Vipallāsakathā.
I am mainly interested in the following part :

Anattani  anattāti,  asubhaṃ asubhataddasuṃ;  Sammādiṭṭhisamādānā,
  sabbaṃ dukkhaṃ upaccagun”ti.

It is the same of Sutta Pitaka Vol 13 : Sutta. Aṅ. (2): catukkanipāto vipallāsasutta, except only the end paragraph which is the sutta's summary by sāriputta-mahāsāvaka :

These four, bhikkhus, are distortions of saññā, distortions of citta,
distortions of diṭṭhi. Which four?
In what is aniccā, bhikkhus, [seeing] permanence is a distortion of
saññā, a distortion of citta, a distortion of diṭṭhi. In what is
dukkha, bhikkhus, [seeing] sukha is a distortion of saññā, a
distortion of citta, a distortion of diṭṭhi. In what is anatta,
bhikkhus, [seeing] atta is a distortion of saññā, a distortion of
citta, a distortion of diṭṭhi. In what is asubha, bhikkhus, [seeing]
beauty is a distortion of saññā, a distortion of citta, a distortion
of diṭṭhi.
These four, bhikkhus, are distortions of saññā, distortions of citta,
distortions of diṭṭhi.
Perceiving constancy in the inconstant,
pleasure in the stressful,
self in what's not-self,
attractiveness in the unattractive,
beings, destroyed by wrong-view,
go mad, out of their minds.
Bound to Mara's yoke,
from the yoke they find no rest.
Beings go on to the wandering-on,
leading to birth & death.
But when Awakened Ones
arise in the world,
bringing light to the world,
they proclaim the Dhamma
leading to the stilling of stress.
When those with discernment listen,
they regain their senses,
seeing      the inconstant as inconstant,
the stressful as stressful,
what's not-self as not-self,
the unattractive as unattractive.
Undertaking right view,
they transcend all stress & suffering.

For the end paragraph in Sutta Pitaka Vol 23 : Sutta. Khu. Paṭisambhidāmaggo Mahāvagge vipallāsakathā, which is the sutta's summary by sāriputta-mahāsāvaka:

These 4 vipallāsa of diṭṭhisampanna-puggaka(sotāpanna) were abandoned(by sotāpattimagga) to arise or not? Some vipallāsa were, but some not. Saññāvipallāsa, cittavipallāsa, and diṭṭhivipallāsa which taking (this object:) "impermanent (khandha) as permanent (khandha)"  were abandoned to arise. Saññāvipallāsa, cittavipallāsa which taking (this object:) "suffering (khandha) as pleasant (khandha)" still arise, but diṭṭhivipallāsa  were abandoned to arise. Saññāvipallāsa, cittavipallāsa which taking (this object:)  "foul (khandha) as beautiful (khandha)" still arise, but diṭṭhivipallāsa  were abandoned to arise. Saññāvipallāsa, cittavipallāsa, and diṭṭhivipallāsa which taking (this object:) "anattā (khandha) as attā (khandha)"  were abandoned to arise.
6 vipallāsa (3 permanent vipallāsa, 3 attā vipallāsa) were abandoned to arise and to take 2 objects (permanent object, attā object). 2 vipallāsa (1  beautiful vipallāsa, 1 pleasant vipallāsa) were abandoned to arise and to take 2 objects (beautiful object, pleasant object), but 4 vipallāsa (2  beautiful vipallāsa, 2 pleasant vipallāsa) were not abandoned to arise. (The conclusion:) 8 vipallāsa (3 permanent vipallāsa, 3 attā vipallāsa, 1  beautiful vipallāsa, and 1 pleasant vipallāsa) were abandoned to arise and to take 4 objects (permanent object, beautiful object, pleasant object, and attā object), but 4 vipallāsa (2  beautiful vipallāsa, 2 pleasant vipallāsa) were not abandoned to arise.

Anattani anattāti (Seeing) non-self as non-self
asubhaṃ asubhataddasuṃ; Unattractiveness as unattractiveness
Sammādiṭṭhisamādānā, (he is) holding on to right view.
dukkhaṃ upaccagun”ti. (He is) above sufferings

I marked this answer down because it included "self/Atman" within brackets. When the realisation of not-self occurs, it is the mind that is above suffering and the mind the holds onto right view (rather than a "self" or "he"). The Pali suttas teach about citta vimmutti (liberation of mind) rather than atta vimmuti (liberation of self). It is proper to not study Buddhism for the purpose of building egoism. In MN 22, the Buddha called studying dhamma to build egoism as grasping a poison snake. With metta

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Is Nirvana the goal, for Zen and Theravada?
What is the main goal for Theravada Buddhism and Zen Buddhism? Is it Nirvana for both or is there any additional differences?
Can the answer be detailed because this is an assignment and I am trying to be as detailed as possible. Thanks so much!

Is that your homework?

A policy for homework questions on other SE sites is to help the OP, not by doing their homework for them, but by helping with their problem. Here I guess the OP would find it helpful if you could give some relevant references, to one or articles which explain "the main goal for Theravada Buddhism and Zen Buddhism", whether it's "Nirvana for both", and/or any "additional differences". I think it would be fine to give several partial answers -- e.g. one person might answer with references about Theravada, while someone else might post an answer about Zen.

The OP is probably able to read a lot already, if they searched the internet and/or this site, about Zen and Theravada and Nirvana. They asked for "detailed", but maybe what they're missing is an overview or summary, of a possible structure for the answer. So maybe a good question is (or a good answer would be), "What several sections or topics could a long and detailed answer contain?" (and, preferably, any reference for each topic).

There is no goal in Zen. To have a goal is spin the wheel of samsara. Zen is all about getting to the basics, which are beyond words and concepts. I should know I have been practicing Zen for seventeen years and I am still a beginner.

If not a goal, then what is the motivation or intent of practicing zen? Surely there is a motivation or intention, right?

That's a good question but if you look at intention and motivation isn't that like desire and what the Buddha taught was samsara is very much like a made up world as stated in the lankavatara sutra. Things are both real and not real. Quite a conundrum! That's the beauty of the Buddha's meditation. But then we have another problem. What is the correct form of meditation that lead to the Buddha's awakening. Is it Vipassana/Mindfulness or is it samadhi, jhana, Zazen or Absolute samadhi?

Isn't it the term "goal" that smells of Samsara? How about the purification of mind, the relinquishment of defilements and the development of wholesome qualities, such as compassion.

@Lanka I think that Zen includes doctrine that "the original mind" is undefiled or something like that.

@ChrisW. That's true - it does. The Ven. Dalai Lama, describes the original mind, as being a glass of pure, transparent water (undefiled). That is its original form/state. When defilements are present its like muddy water.

@Lanka Maybe it's analogous to this dichotomy -- one (method) is a gradual process (towards a result), and the other (method) "takes the result as the path".

@ChrisW. Yes, it seems that way. I would think OP's answer addresses the first method, i.e. "the gradual process, towards a result".

And what is the noble search? There is the case where a person,
  himself being subject to birth, seeing the drawbacks of birth, seeks
  the unborn, unexcelled rest from the yoke: Unbinding. Himself being
  subject to aging... illness... death... sorrow... defilement, seeing
  the drawbacks of aging... illness... death... sorrow... defilement,
  seeks the aging-less, illness-less, deathless, sorrow-less, undefiled,
  unexcelled rest from the yoke: Unbinding. This is the noble search.
   -Ariyapariyesana Sutta

"aging-less, illness-less, deathless, sorrow-less, undefiled, unexcelled rest from the yoke: Unbinding" here refers to Nibbana. So yes, it is the goal in Theravada Budhhism.

I think this question might go unanswered so I'll give it a try.
This answer isn't detailed, but it's how I might structure an answer. The structure is kind of historical. For more details you can google for words I quoted (for example sila).

The earliest Buddhist Dhamma is maybe the "Four Noble Truths": which are about suffering or unsatisfactoriness ("dukkha"), the cause, and the cessation of suffering -- and the "Noble Eight Way", which is the path leading to the end suffering.
So the goal is to end suffering ... or to complete the way, to do what needed to be done etc.
The "Noble Eightfold Way" can be summarised as the "Threefold Training". Some of the training is seen as being more intended for monks than for laypeople.
The bit intended for everyone (including laypeople) is morality also known as "sila" (including "the precepts") -- of which you get summaries like this or this. These are maybe not the goal (or maybe they are the goal for laypeople), but a goal. Or maybe the goal is "sukha", maybe a good rebirth.
The other two parts of the three-fold training are concentration and wisdom: so those might be called goals too.
The "suttas" (which are transcripts of the Buddha's doctrine) are fairly long. Two other parts of the "Tripiṭaka" are the "Vinaya" (the monastic rules, for monks and nuns, also from the Buddha) and the "Abhidhamma" (which I think is a scholastic analysis or reworking, commentary, on material in the suttas). It's quite lengthy.
I'd say that it (at least the suttas) is almost all about the Way, rather than about the Goal.
The Way includes abandoning "fetters", also "hindrances" and "outflows" and so on. Because these are the Way, these too could be seen as goals.
Nibbana is one of names for the Goal -- it's one of many names.
I think that, later, people discussed the metaphysical nature of nibbana: "does it exist?" etc.
Buddhist doctrine migrated via China. Some scholars say it was influenced there by Taoism. From there it reached Japan. So fas as I know, at some point some Japanese masters decided there was too much scholarship (too much text, perhaps) ... and put more emphasis on meditation. It continued the tradition of learning from teachers ("lineage"), living in monasteries, and so on.
One of the early (Theravada) doctrines (from the Four Noble Truths) is that suffering is caused by desire, that suffering ceases when desire ceases: so you get suttas like this. I don't know much about Zen, I think that one of its doctrines is to meditate without a goal (which may be similar to "without desire", and is relevant to your question). Another value seems to be spontaneity -- maybe not a goal in itself but a characteristic of an "enlightened" state of mind -- which ("spontaneity") is, maybe, not one of the explicit Theravada values? I'm not sure whether to see this as a lack of "attachment" (as might be understood by Theravada), and/or as something with a Taoist influence.
Zen Buddhism doesn't only exist in Japan: also in Vietnam and Korea. A reason that Zen is famous in the English-speaking world is that it was one of the first forms of Buddhism in the United States.
All that said, the goal might be similar. Here's a quote from Thich Nhat Hanh (a famous Vietnamese Zen monk):

Oprah: Thank you for the honor of talking to you. Just being in your
  presence, I feel less stressed than when the day started. You have
  such a peaceful aura. Are you always this content?
Nhat Hanh: This is my training, this is my practice. And I try to live
  every moment like that, to keep the peace in myself.
Oprah: Because you can't give it to others if you don't have it in
  yourself.
Nhat Hanh: Right.
Oprah: I see. I know that you were born in Vietnam in 1926. Is there
  any wonderful memory of your childhood that you can share?
Nhat Hanh: The day I saw a picture of the Buddha in a magazine.
Oprah: How old were you?
Nhat Hanh: I was 7, 8. He was sitting on the grass, very peaceful,
  smiling. I was impressed. Around me, people were not like that, so I
  had the desire to be like him.

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text:
How much concentration do I need to practice vipassana?
I have read some articles and book, it says that you need to develop some basic level of concentration before you can start practicing vipassana(insight) meditation.
What are the criteria to know if I already reached that basic level of concentration?
Thank you very much!

In Tibetan tradition, before you can do Vipashyana, you have to practice Shamatha-type meditation until you learn to attain so-called "Calm Abiding" or "Fully Pacified Stable One-Pointed Effortless Meditative Equipoise".
According to a traditional presentation, Calm Abiding is considered attained when a meditator can effortlessly focus on a chosen object of observation, without getting distracted and without falling into lethargy, for a substantial period of time.

"substantial period" is  a subjective measure. Some say it is 2 minutes, some say 10 or 15.
"object of observation" means any object or theme, like a flame of a candle, flower, a far away mountain peak -- or a visualized/imaginary object of any kind, the most popular being an image of Buddha statue. (With imaginary objects it is best to use something very familiar that you remember very well.)
"without getting distracted" means without forgetting about meditation and getting carried away in thoughts.
"without falling into lethargy" means, without getting sleepy or even losing clarity of mind.
"effortlessly" means without fighting with oneself over distractions and lethargy.

Here is a set of more detailed guidelines on achieving Calm Abiding: an excerpt from a lecture given by Gelug meditation master Lati Rinpoche.

Hi Andrei, thank you very much for answering my question on point and even made it in bold. Sometimes whenever I meditate, I always start with samatha and then proceed to vipassana. But I didn't have any clue when should I switch, so I sometimes switch in between samatha and vipassana. Whenever I feel like I can't concentrate anymore I switch back to samatha, is it right to do that way?

Yes, that is absolutely right, to switch to samatha when you lose concentration in vipassana. In fact, in my understanding the Buddha meant these two meditation aspects to be practiced together, one supporting the other. Learning to tranquilize the mind is a source of insight into how mind works, and insight into mind workings leads to an increased ability to tranquilize the mind. So even though for absolute beginners they are taught separately, eventually it becomes one meditation that has elements of both. @r721n3lmn

Your reply and comment cleared much of my confusions. Thanks a lot, much love.

I recently did a 10 day Silent Retreat based on Vipasanna Meditation by S. N. Goenka.
https://www.dhamma.org/en-US/index
There are no prerequisites for the course and it is given in many centers around the US, Canada and other parts of the world.  I recommend it highly.
I did read a recommended book, Art of Living by William Hart (The Art Of Living as Taught by S.N. Goenka from Amazon).  I also practiced meditating on my own for two months before I did the course – there is usually a pretty long wait list for the course at least here in Texas.
You will be minimally qualified to do Vipassana meditation when you leave the course and follow up practice on your own or through a Vipassana Sangha is recommended.

To practice Vipassana, what you need is right mindfulness or Samma-sati. Concentration comes as you develop right mindfulness. There are actually four ways of doing it. You can develop concentration first and then switch to Vipassana or develop both concentration and Vipassana in tandem or develop Vipassana first and then switch to concentration. Whoever claims that developing concentration first is the only way is misinformed. Read the Yuganaddha Sutta for details.

In SN Goenkas course we spend first 4 days developing concentration of breath called anapanasati. The sutta you have referenced is addressed to monks. I think it is safe to assume that 99% of those monks all had developed basic concentration skills. How can you practise Vipassana without developing concentration first. I mean you need to concentrate on the sensation on body.

@BodhiWalker "I think it is safe to assume that 99% of those monks all had developed basic concentration skills." This is a wrong assumption. I don't believe even SN Goenka claims that his technique is the only way :)

if you can teach people Vipassana without developing faculty of concentration I will be deeply impressed. Let me know exactly who teaches and where is this taught...I will try my best to attend that retreat or course.

I suggest you to study the Mahasi Sayadaw technique. Concentration comes as you develop mindfulness. Also read the Bāhiya Sutta. See the technique taught there by the Buddha himself.

I've read somewhere, that those people who can go practice vipassana directly are people that already have some basic concentration. In the article I read, it says that those people are for example: people who are living in country side that aren't used to fast paced lifestyle like those who lives in a big city, so when they learn to practice vipassana they can learn it directly.

@r721n3lmn Almost everyone one has basic concentration. Otherwise how would you even count from 1 to 10 or remember what you need to buy in the grocery? :)


text:
Hereditary illness and kamma
Many physical and mental illnesses are genetic or hereditary, whether partially or completely, the contributing factor is genetic, nevertheless.
For example, you are born into a family that has genetic illness e.g. anxiety disorder, compulsive disorder, cancer, diabetes, to name a few.
The question is, since genetic or hereditary illness will then pass down to your children.
If you get married and have children, as parents, are you doing bad kamma?

I guess this question is, specifically, about whether it's especially bad kamma to have children if you know you have a genetic/heritable illness.

Are you asking for everyone's opinion? Or for references (ancient and/or modern)?

Related topics: Should a Buddhist have Children? and Should person with schizophrenia have children?

Hereditary illness or not...the offspring you will produce will become old, fall ill and die. The dukkha is inevitable. We may as well say that dukkha is hereditary to all humans so  should we have kids?
If your intention in having a child is good, if the child is born out of love and not lust, if child is born not out of any form of sexual misconduct...then you will be fine...there will be no bad kamma.

What do you mean “kamma will be merciful?” Can you elaborate in your answer the intended meaning here? Is kamma like a judge or jury or a god in that it weighs the evidence and punishes or rewards people?

@Yeshe Tenley my sincere apologies, I was not being technically right. I was trying to be poetic ascribing it somewhat anthropomorphic role. I changed the answer.

@BodhiWalker but we know heredity will be passed down to our children, yet we still want to have children. Would that be the same as you know there is an ant on the floor yet you step on it, if this counts as killing then why the former one doesn't count as passing down the illness?

@B1100 no it will not be same. If you deliberatly step on ant your intention is to harm life that is bad karma. In case of giving birth to child your intention was not to harm her. But still if you are filled with so much compassion towards unborn child you should not have child. You might be passibg down the illness but that is not your true intention, simultaneously you are also giving her a chance to become a Buddha. In any case suffering is inevitable.

@BodhiWalker He is aware there is ant, steps on it but his intention is to go to work, not killing. The same thing as heredity illness, it's not the parents' intention to pass down the illness to the child. But why the former one still counts as killing although his intention is to go to work yet the latter one does not count as passing down the illness, both of them do not have intention to harm, right? When we aware about something, does it mean there is intention?

@B1100 In my opinion, if he steps on an ant being fully aware that he is doing it, the the intention may not be of harming but then he have not developed the parami of kindness and compassion towards lowely beings. Also here intention is not going to work, going to work is his temporal goal. While stepping on ant he has no good or bad intention, he is simply mindless. So it wont be a bad karma but karma nonetheless. So if you are suggesting that both acts are dont without awareness and mindfulness then i thinkbthey will both be sinilar karma. IMO if we can be aware and there may or may not be

@B1100 2/2 ...contd  if we define intention as delibrate act with full awareness of act with a pre defined purpose then that becomes an intention. However I can do things with utmost awareness without having anyintention whatsoever...like dancing in the rain...

@BodhiWalker if you have participated in meditation class or retreat particularly mindfulness meditation, the teacher will tell you even moving your hand or raise your leg need to have intention, let alone dancing. This is getting complicated, if stepping on ant has intention then why having children is not passing down the illness, I just don't get it.

@B1100 ya I think we are at odds on semantics of the word 'intention'. I will do some research on this.

The occurence of genetically inherited diseases are in most cases, not 100%. There is always a chance that they may or may not manifest. Part of this depends on lifestyle and environmental reasons as well. Some diseases like diabetes and heart disease can be avoided or delayed by lifestyle modifications.
Genetics can be quite complex - two siblings who are not identical twins, may not experience the same type of diseases or medical problems.
That being said, kamma depends on one's intentions. If you had children without evil intentions, then it's not bad kamma.
Whether your children would get a specific disease or not, cannot be known with perfect certainty. However, with perfect certainty, we can say that they will grow old, experience disease and death. They will also experience pain and pleasure. They will also burn with the fires of passion, aversion and delusion, for as long as they are unenlightened.
The fact that your child would experience sufferings of any kind, is not caused by their birth. Birth is merely a symptom of suffering. It's not the cause of suffering.
You should not feel responsible for the phenomena of samsara. It moves along perfectly fine on its own.

Shantideva I think says that we should feel responsible for Samsara in the sense that we should make it our goal to dispel the miseries of the world... do you disagree? The fact that our mere existence in Samsara is a condition for others suffering is one aspect of the first noble truth. @ruben2020

@ruben2020 you can also step on an ant without evil intention. But I believe when you step on ant you cannot have other intention other than evil intention, then why it doesn't work the same as having children and passing down the illness?

Your Karma, good or bad, will depend on how you treat, raise, and teach your child. It is What you do with him/her, that will result in good/bad/neutral karma.
Hence, by just bringing a child into the world, it is neither a good or bad karma, it is neutral.


text:
Does Nibbana mean not self?
I have found a text which states that

nibbāna is a description meaning not-self.

The meaning of the text is clear. Nibbana is nothing but not-self.
Moreover I have also found a sutta(SN22.45) which says that after understanding and realizing not-self the person attains Nirvana.

At Savatthi. “Bhikkhus, form is impermanent. What is impermanent is
  suffering. What is suffering is nonself. What is nonself should be
  seen as it really is with correct wisdom thus: ‘This is not mine, this
  I am not, this is not my self.’ When one sees this thus as it really
  is with correct wisdom, the mind becomes dispassionate and is
  liberated from the taints by nonclinging

.
.
.

“By being liberated, it is steady; by being steady, it is content; by
  being content, he is not agitated. Being unagitated, he personally
  attains Nibbāna.

My question is :Does Nibbana mean not self?

Much like Sankha and Ruben2020 have said, I think it is imperative to understand that selflessness is an apt description of all persons and phenomena, including nirvana. That is, there is nothing which isn't selfless. Another way of saying this is that all things lack inherent existence; including nirvana. There is nothing neither existent nor non-existent that cannot be described as utterly lacking a self.
But nirvana is not a person so how can it be said to be selfless? Also, it is not an impermanent phenomena so how can it be said to be selfless?
One part of the confusion here is that it is usually thought that the Pali Canon is only part of the First Turning of the Wheel of Dharma. However, I don't think this is strictly true. The Second Turning of the Wheel of Dharma can be found in the Pali Canon. In Sutras like this and for instance the Kaccayanagotta Sutta we see the Buddha giving teachings that to my mind are very clearly part of the Second Turning. These teachings are elaborated on by the Buddha in strictly Mayahana Sutras and by the Virtuous Teachers such as Nagarjuna. Nagarjuna's Fundamental Treatise of the Middle Way devotes an entire chapter to nirvana and how it is selfless. So how do the Second Turning Virtuous Teachers say that nirvana is selfless?
Nirvana is not a person and yet it utterly lacks any inherent existence. This is how it is said to be selfless. Nirvana is not an impermanent phenomena and yet it utterly lacks any inherent existence. This is how it is said to be selfless.
Thus, the correct understanding of the selflessness of Nirvana cannot be arrived at without understanding the subtler meanings of selflessness. Understanding selflessness through things not existing permanently, unitarily and independently is the coarsest understanding and this is not sufficient for understanding the selflessness of Nirvana.
Now, does that mean being selfless is a completely sufficient description of nirvana? No. More needs to be said. Nevertheless, nirvana is indeed selfless.
Moreover, understanding the selflessness of all things is essential to gaining our liberation from cyclic existence. Directly realizing the emptiness of all existent and non-existent things and regarding all this as a morass of utterly unreal concepts and appearances is how we arrive at the doorstep of nirvana. I hope this helps.
Finally, I'll note that nirvana comes in two types: with residuals and without. According to my tradition Nirvana without residuals is only attained by fully enlightened Buddhas or Arya beings while in meditative equipoise directly perceiving emptiness.

If the OP wants to understand anatta, it might be precise to distinguish it slightly from sunyata. When you mention the "selflessness of all persons and all phenomena" I guess you might be talking about their "emptiness", which is maybe not quite the same doctrine as Sankha's saying "Everything is not-self". And your last paragraph about "realising emptiness" sounds like Second Turning too. Not that I'm disagreeing with you, I say this because I hope it may be helpful to readers to understand why (or based on what doctrines) different people have different answers.

Thanks @ChrisW, I'm trying to figure out how to make it more precise or helpful. The selflessness of persons and selflessness of phenomena at the subtlest level are exactly the same, but this is clearly explained in Second Turning or Madhyimaka doctrine as you say. However, the OP question and Sankha's answer is clearly showing anatta being used to describe not a person, but a phenomena: that of Nirvana. I think you need Second Turning or Madhyamika explanations for this.

To my (not well-educated) mind, anatta means "not me" (and "not mine" and so on). For example, this body is "not me", and this thought is "not me", and this feeling is "not me", and so on. And, that tree isn't me. Whereas sunyata goes slightly further, and says for example, "that tree isn't only not-me ... it isn't even itself!" Saying "nibanna isn't me, isn't mine, isn't my soul" is one thing, and saying it's "empty" is another, IMO. And I think that according to the Pali canon, abandoning wrong self-view is a first stage of enlightenment (important even before a more "final" nibbanna).

@ChrisW hmm, I don't think that is what it means in my tradition even for the Pali canon. In my tradition, anatta and sunyata are both meaning the same thing at the subtlest level without regard to object: the lack of inherent existence. At other levels and under different tenet systems they can be divided with regard to object: persons vs non-persons and have different meanings. For instance, the Vaibhashikas and Sautrantikas do not recognize the selflessness of non-persons such as Nirvana.

In my tradition, anatta and sunyata are both meaning the same thing at the subtlest level without regard to object: the lack of inherent existence. That's as may be; and I take it that, perhaps (I haven't read his work), Nagarjuna is careful not to contradict the suttas. Still I think that e.g. this topic says that "sakkhya ditthi" (a.k.a. "belief in a self") is the (wrong) view that the five aggregates are "self": and that "anatta" is an extension of that, that it's wrong to view anything (any sankhara or even any dhamma at all) as "self".

Hi @ChrisW, I'm having a hard time understanding if there is any daylight between us. I've edited the answer to better explain that I think this OP is about something that can only be understood correctly through Second Turning teachings where distinctions between anatta and sunyata largely dissolve. Taking anatta to mean a lack of permanent, unitary, independent person is not sufficient to explain what is meant by nirvana to be selfless.

I think it's a better answer now, with additions, though I up-voted it long ago. I wouldn't tend to say that "Nibbana is selfless" though (except when I must) -- I see it more as referring to the result of "abandoning desire", or something like that (not only desire but attachments, maybe views, and outflows, and hindrances, and so on).

Everything is not-self including Nibbana. But Nibbana is much more than that. It is the end of suffering.

This is good! Perhaps it would be more clear to say that 'Nibbana means much more than that' instead of the word 'is'? Also, maybe the answer could be elaborated by explaining how understanding non-self, both in persons and phenomena, from the coarsest level to the most subtle, can lead to Nibbana?

@YesheTenley what's wrong with using 'is'?

Nothing per se, just that I think part of OP's question revolves around whether a description of something is necessary and sufficient or whether more needs to be said. I think 'is' implies the former, where 'means' implies the latter, but I'm probably wrong and your usage is fine.

I think realisation of Anatta is a necessary and sufficient condition for attainment of Nirvana. If not then what is/are the necessary and sufficient condition/s for Nirvana ?

This is @SankhaKulathantille answer so I'll let him speak for himself...

When the realization of Anicca/Dukkha/Anatta becomes all encompassing, the meditator attains an absolute certainty of one or another of the three characteristics and this leads to a release. This release leads to an experience of cessation, where there is no arising of sense experience (including mental sense experience). This is the realization of nibbāna. Read more here

Anatta or not-self is a characteristic of all phenomena (including Nibbana), regardless of whether they are conditioned or unconditioned, compounded or uncompounded, permanent or impermanent.
Nibbana is the phenomena which is the end of suffering. It's unconditioned, uncompounded and not impermanent. It's also not-self.
Samsara and dukkha (suffering) are also not-self.
Even a stream winner or sotapanna would have overcome the self-view but would not have attained Nibbana yet. In order for the stream winner to reach Nibbana, he needs to overcome the remainder of the ten fetters.

Is there any quote to support "Even a stream winner or sotapanna would have overcome the self-view but would not have attained Nibbana yet." ? Without Mindfulness how can anyone ever overcome the self-view? Body, feelings, perceptions,consciousness,volitional formations arise...only a mindful person can declare them as not-self.

This is not a quote, but the fact that the Buddha made a distinction between an Arya being (ie., sotapanna) and once-returner, non-returner let alone an Arhat or Buddha makes it quite clear that stream winners have more to do, right? The path is not complete at sotapanna, right?

@DheerajVerma AN10.13 states: "And which are the five lower fetters? Self-identity views, uncertainty, grasping at precepts & practices, sensual desire, & ill will. ... And which are the five higher fetters? Passion for form, passion for what is formless, conceit, restlessness, & ignorance." And MN118 states: "In this community of monks there are monks who, with the wasting away of [the first] three fetters, are stream-winners".

@ruben2020 It is the teaching of Dhamma which uproots all the fetters. What is Dhamma ? Dhamma is the teaching of Anatta. What is Anatta ? Anatta is recognising and realizing for example that eye is not self. This statement alone uproots many fetters. Here is quote from Buddha himself. You have made a valid point but I guess knowing what is anatta(identity "view") and realizing what is anatta are two very different things.

The meaning of the text is clear. Nibbana is nothing but not-self.
I don't think that's clear.
He're the original text:

Aniccā sabbe saṅkhārā,
  dukkhānattā ca saṅkhatā;
  Nibbānañceva paññatti,
  anattā iti nicchayā.

I translate as:

[impermanent] [is every] [conditioned thing]
  [painful and not-self] [and] [conditioned]
  [in-the-case-of nibanna] [description]
  [not-self] [thus it is] [certainly]

I think that may be saying that "nibanna is a description" and "therefore not self".
I don't know how to reconcile that with the doctrine that "nibanna isn't conditioned" (or "is unconditioned").
But anyway I think the chief characteristic of nibanna is that it's a state that's free of attachments and cravings ... and not just "free" but "permanently free" ... and therefore free of dukkha.
The fact that nibanna is also anatta is a kind of a side-effect (e.g. a lack of attachment to "self").
I think it's wrong to say "Nibbana is nothing but not-self" or that "Nibbana is only not-self" ... I think that nibanna is more (or less) than that, it is unattached to (unconditioned by) anything and everything, not just "self".
My question is: Does Nibbana means not self?
I think it is not-self, but it doesn't mean "not-self".
Like France is a country, but doesn't mean "a country".
The word "meaning" was added by the English-language translator/translation you quoted, fwiw.
Is there any quote to support "Even a stream winner or sotapanna would have overcome the self-view but would not have attained Nibbana yet."?
I hope you'll find the answers to this topic: How are 'conceit' and 'identity-view' not the same?

You said, "I don't know how to reconcile that with the doctrine that "nibanna isn't conditioned" (or "is unconditioned")." I'd suggest that a careful study of Chapter 25 of Nagarjuna's Fundamental Treatise of the Middle Way along with the excellent commentary by Je Tsongkhapa in Ocean of Reasoning might help to understand this.

I have found a text which states that

nibbāna is a description meaning not-self.

Actually, that translation is mistake, because the translator has not enough knowledge to translate it. So, what is the knowledge which the translator has to know to translate this text?
VN Pañcasitikakhandhaka & VN Parivāra identify Upāli authored that text; Upāli is Sāriputta's student; And sāriputta authored abhidhamma-pitaka; So there are many abhidhamma's style text inside VN Parivāra; Therefore, If the translator want to translate VN Parivāra's pāli, he need abhidhamma-knowledge:

Aniccā sabbe saṅkhārā, dukkhānattā ca saṅkhatā;
Nibbānañceva paññatti, anattā iti nicchayā.
Saṅkhāra, which means saṅkhata(effect-saṅkhāra)*, is anicca&dukkha&anattā;
But only nibbāna&paññatti which are explained just as anattā.

*Saṅkhāra, which means cause-saṅkhāra, use in more fixed  meaning word, such as saṅkhāra-khandha, saṅkhāra-paṭiccasamuppāda. You can notice it in each context, because it is already appear clearly.


text:
Are there any translations available from the Gandharan Buddhist Texts? When will they be available?
Please find reference for the texts:
https://en.wikipedia.org/wiki/Gandhāran_Buddhist_texts

Like these ones?

https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Dstripbooks&field-keywords=Gandhari
https://www.thriftbooks.com/a/richard-salomon/877720
http://www.rhinoresourcecenter.com/pdf_files/138/1386654811.pdf

Amazon lists 3 pages of books. I didn't check all three pages though.
But it should be enough to get you started.
Have fun. :)


text:
What is wisdom in vipassana meditation?
Having seen that anger disappears after noticing attraction and aversion of the mind towards thoughts, attraction and aversion have disappeared.  Feel like there is no core on mind objects. Is that anatta?

Well, if you wanted to call this something, then wisdom would be suitable. However, I would allow the conventions of chronology to take further course. Let the passage of time reveal its activity.

A wisdom excluded from the Dhamma-discipline is not a perfect wisdom. Therefore, there is no liberation where the Dhamma and Discipline are absent. It is in the Supreme Buddha’s Dhamma that the perfect concentration is described. It is that Dhamma that the contemplations are described as this is the first contemplation (Dhyāna), this is the second contemplation, this is the third contemplation, and this is the fourth contemplation. If one develops wisdom, it has to be a wisdom that is being developed praising the Dhamma and the Discipline. This is wisdom in vipassana meditation. In order to come to this Wisdom, one needs to sever and totally obliterate the three bonds of Nichcha (thinking that one can maintain a permanent state of mind), Sukha (believing that which is happiness/good can be maintained), aththa (thinking that this is a stable, fulfilled state of mind). If “atta” is “in control” or “has essence”, and the opposite of that is the anatta in Tilakkkhana: “one is helpless in this rebirth process”.

Question is whether the stage is anatta. --The answer lies hidden in itself in writing this question on this site. Still the questioner is present then how can it be "anatta. These signs are all of the tranquil  mind to which we are unknown since many lives.Furthermore the mind itself ,being very clever to sustain itself, ask or give false feeling of the very big big states . It goes no telling ,now its ok, you have reached the destination , this is what is anicca,anatta, wts the meaning in continuing . But not be foolished by tricky mind and go on practising. The experience/wisdom of anicca/anatta ,whenever it happens,you will not even on this site also to ask question also. perhaps  you may be then be resolving difficulties/guiding the path goers.

Good question!
Vipassana, the tranquil mind, is the core.
When emotions arise, the tranquil mind observes and assesses before the conscious is involved. Instant emotional, physical and intentional reaction is an uncultivated reaction - which has a tendency to result in more, similar reactions (from the one in question or uncultivated others involved).
In an uncultivated individual the emotions rule the self. This is the result of lack of understanding of Anatta and somehow the individual is putting conscious effort into the stagnation of their naturally dynamic emotions.
Emotions are naturally dynamic and a result of environmental influence, which is also dynamic - so in that sense Anatta is applicable. If one cultivates the practice of unbiased observation, the result will be an understanding and application of Anatta to the heart. The tranquil mind will recognise the burning heart and dualise the self. When the self becomes two, the emotions don't rule the mind and the mind doesn't rule the emotions.
Cultivate in harmony


text:
What is meant by escape from all signs?
Good will , compassion , equanimity etc are objects of meditation.
Good will is used to escape from ill-will. Compassion is used to escape from viciousness. Equanimity is used to escape from passion.
All the above ideas are familiar to me and I understand them well.
Along the similar lines there is a concept of signless (I guess signless is also an object of meditation). Signless is used to escape from all signs.
Following quote from aṅguttara nikāya explains signless :

“Furthermore, there is the case where a monk might say, ‘Although the
  signless has been developed, pursued, handed the reins and taken as a
  basis, given a grounding, steadied, consolidated, and well-undertaken
  by me as my awareness-release, still my consciousness follows the
  drift of signs.’ He should be told, ‘Don’t say that. You shouldn’t
  speak in that way. Don’t misrepresent the Blessed One, for it’s not
  right to misrepresent the Blessed One, and the Blessed One wouldn’t
  say that. It’s impossible, there is no way that—when the signless has
  been developed, pursued, handed the reins and taken as a basis, given
  a grounding, steadied, consolidated, and well-undertaken as an
  awareness-release—consciousness would follow the drift of signs. That
  possibility doesn’t exist, for this is the escape from all signs: the
  signless as an awareness-release.’

I am having difficulty in understanding what are signs?
My question is : what is signless (or what is sign) and what is meant by escape from all signs?

According to Mahayana interpretation, "signs" or "marks" are concepts, or conceptual designations, also known as preconceptions.
The problem with conceptual designations is that we tend to confuse them with reality (=to reify; noun "reification"). To give a canonical example, when someone is attached to his own personal stereotype of what an "attractive woman" should look like, when he meets one that matches his stereotype he no longer sees her as a complete person, instead he only sees his own concept of woman, he sees a sexual object! Then we tend to look with our conceptual brain, instead of looking with an open mind. Then, all we see is our preconceptions or biases - instead of seeing what actually is. Not only we see nothing but our preconceptions, we completely confuse them for reality, we think that what we "think" is what really "is" - but it is not, we see our own mental fabrication! Then on the basis of that fabrication, we develop certain attitude toward the object - for example we want to make acquaintance with the woman, with an implicit intent to get close with her. This is called "following the drift of signs".
Another example of this is racial stereotyping. You see a person of a national origin that you generally associate with ignorant violence - and then all you see is your preconception, you no longer see the real person. On the basis of this you develop aversion to this person, which ends up causing a conflict.
This happens with inanimate objects as well. Once we know that a given object is "a tree" - we no longer really see it as-is, we see our concept: "a tree". It takes a special effort to unsee our abstract concept and see the actual tree.
According to Mahayana, the entire Samsara is an illusory world completely made of such concepts! The notion of "I" or atman is one of such preconceptions. It is on the basis of attachment to preconceptions that we have unsatisfied craving, which manifests as suffering. Complete cessation of reification is "escape from all signs".
This is a rather simplified presentation, it actually goes much deeper than that, but this can get you started. Entire Mahayana was born from study and development of this teaching, passed in the oral form from Buddha's students to next generations. In Mahayana we refer to this as "shunyata" and "prajna-paramita", but it is also present in the Pali Canon in quite a few places like this one, using terms like "groundless", "having no position", "signless" etc.

I think this is a good answer and I've up-voted it accordingly, but I have a question about it... some tenet systems maintain that giving up conceptual thought is enough to arrive at the understanding of emptiness. In other words, when the mind empties of conceptual thought is that enough to directly realize emptiness? Signlessness? Or is there more work to do? Do we need to just stop thinking or having conceptions? Relatedly, when an ordinary person perceives (as opposed to conceives) objects... do the objects appear truly or inherently existent? Or do we perceive them as they really are?

In my understanding, giving up conceptual thought won't cut it. We're not trying to become animals here :)) According to Mahamudra and Dzogchen teachings one has to achieve complete "spontaneous presence", for which conceptual groundlessness plays a merely instrumental role. Concepts are like 2D vision, and this is like 3D vision.

@AndreiVolkov Buddha calls for abandoning of sign of forms, of sounds, of odours, of flavours, of tangibles, and of mental objects. If sign is a concept then do we have to get rid of the concepts of the forms,sounds,odours,flavours,tangibles and mental objects? Buddha doesn't say to abandon preconceived notion of beauty but to abandon the sign of forms.

That's right, it's not as much to abandon all preconceived notions, as to learn to not be their slave, @DheerajVerma It's a sort of multidimmensional cognition that makes one immune to suffering arising due to attachment to views.

There's some other discussion of it here (with lots of references): Understanding animittā (signlessness) as in AN6.13
I think that "sign" i.e. nimitta is a vague or general-purpose word, like the English word "attribute" or "aspect" or "characteristic" -- when I say that word is vague or unclear I mean because different things have different characteristics (different appearances) -- perhaps I should call it an abstract word, if it's one word that describes character or whatever it is that all (different) characteristics have in common.
As well as being used to describe sense-objects, the word ("sign" or "nimitta") is often used (or is more frequently used, in Buddhist talk) to describe meditation stages or "attainments" (e.g. here or here).
Volume 19 of Piya Tan's Sutta Discovery series consists of topics related to "Nimitta".
SD 19.7 starts with different definitions of Nimitta ("object", "basis", "condition"), and how the word is used in the context of meditation.
But his paper which describes "signless concentration" is later, i.e. it's an element of volume 24 which describes "mental concentration (samadhi)" -- see The Discourse on the Question of the Signless Concentration of Mind which begins with,

The term, “signless concentration of mind” (animitta ceto,samādhi) is not fully explained in the
  Nikāyas, “but its placement after the eighth formless attainment [of S 40.9] suggests it is a samādhi qualitatively
  different from those attained in samatha meditation.”

I think it's related to the topic in SD 19.14 -- "Theme: Sense-restraint & wise attention: how to master the senses". A lot (but not all) of that is Abhidhamma material -- its topic is the formula which appears in several suttas:

Here, bhikshus, when a monk sees a form with the eye, he grasps neither its sign nor its
  details.

In that context I think that a sign is your first impression of something, and its details are what you discern afterwards if you then focus on that thing.
When you get a first impression of something the (unmindful or "unreleased") consciousness will "follow" the sign.

I assume this was downvoted by Dhammadhatu and I don't like when the answerers downvote each other's answers. Upvoting can be reserved for special cases when an answer is truly awesome, but downvoting because you disagree... naturally alternative answerers are very likely to disagree with each other. So I'm upvoting this and hoping the other answerer can remove his negative vote?

I assume the same (and felt a passing dislike of that too) I suppose downvoting is justified when an answer is wrong (or even "not useful") -- though apparently "revenge downvoting" as well as "sympathy upvoting" are also sometimes a thing on SE, but aren't to be encouraged much. IMO I might prefer that a downvote (intended as criticism) were accompanied by an explanatory comment, but what can you do, one cannot require that of downvoters. ATM I only assume this answer was downvoted because it references Piya Tan, discourse.suttacentral, and the Visuddhimagga, none of which he finds agreeable.


text:
Spontaneity in Zen
This Zen Buddhism article starts with,

Zen often seems paradoxical - it requires an intense discipline which, when practised properly, results in total spontaneity and ultimate freedom. This natural spontaneity should not be confused with impulsiveness.

What would they mean by "intense discipline" there, for example ... is it the routine in a monastery?
More centrally, to this question, what is the role of "spontaneity"? Is it a goal? A means to the goal? A side-effect or symptom of having reached "the goal"? Is spontaneity practised somehow, or is that a paradox?
Is there famous (written and translated) Zen doctrine on the subject ... an explanation by someone?
Does it (or something like it) exist, as a value or as a goal or whatever it is, in other schools of Buddhism (e.g. Theravada, or ...)?
Is it spontaneity but within some limits? For example, within the limits of "ethical rules" ... or within the limits of, I don't know, calligraphic and/or other arts, for example?
Assuming it's a well-known concept, is "spontaneity" the right word, the right translation for it? What could be other translations? What's the original (pre-translated) word or words?

Does it (or something like it) exist, as a value or as a goal or whatever it is, in other schools of Buddhism (e.g. Theravada, or ...)?
Yes, it exists in Mahayana in general. From a Mahayana viewpoint, the mind of a buddha is free from conceptualization, and is effortless and free from intentions. (at least intentions that are conceptual consciousnesses, if not the omnipresent mental factor of intentions).
This effortlessness is often translated as naturalness, spontaneity, etc. In Chinese, the term is Tzu-jan (or ziran).
But while it is relevant on a soteriological path in Zen, it is not relevant in this specific way in other traditions or practices, to the exception of Mahamudra, Dzogchen and Tantra in general.
In China, it was a central concept to Confucianism and Daoism before Buddhism was introduced. It then became significant in Buddhism as well. The three teachings (Confucianism, Daoism and Buddhism) all relate to this effortlessness / naturalness but they vary greatly in terms of soteriological paths.
Whether we speak of Confucianism, Daoism or Zen, the idea is to act in accordance with circumstances, as opposed to acting in accordance with abstract principles that are general and not fitting particular circumstances. The following koan conveys this idea:

A monk asked Seigen, “What is the essence of Buddhism?” Seigen said,
  “What is the price of rice in Roryo?”

According to commentaries, the meaning is that when rice is scarce, the price is high. Similarly, the essence of Buddhism depends on contexts. A Dharma practitioner must be adaptable and spontaneous/natural.
In the Chuangzu (a Daoist text), it says:

When a man shoots an arrow to win a tile he is skillful. But if he is
  trying to win a silver buckle he starts getting nervous. And if he’s
  competing for gold he almost loses his mind. His native skill is the
  same in each case, but because he has something to lose, he overvalues
  the external. Whenever the external is prized, the internal gets
  clumsy.

To simplify and resorting to an analogy: From a Confucian perspective, in order to play piano "freestyle", playfully and effortlessly, one must have trained before, abiding by the rules, rehearsing classics, etc. On the other hand, the Daoist approach is more like this: From the start, one has to drop off one's intentions and opinions and not try to control ways and outcomes for, by doing so, he is getting in his own way. One already possesses "the native stuff", he just has to drop off whatever is superfluous. By dropping off, nature reveals itself. (that might echo Dogen's way of characterizing his satori experience as a "dropping off of body and mind")
Zen is very complex and multi-faceted. The so-called sudden teachings are closer to Daoism while the so-called gradual teachings are closer to Confucianism in its approach of rules, classics and traditions.
In terms of soteriological path, what is unique to Zen is that Zazen is to be taken in relation to the whole of Buddhist teachings, especially Mahayana. Some teachers are more or less study-oriented (like Zongmi, Yanshou, Chinul, and even Dogen, etc) and others are not.
I would advise the following books:

Effortless Action: Wu-wei As Conceptual Metaphor. By Slingerland.
Yongming Yanshou's Conception of Chan, by Albert Welter.
Collected Works of Chinul, Robert E. Buswell Jr.

And a few valuable Daoist books that are more accessible than the Tao Te Ching. For instance, the Chuangzu and the Liezhi.

Why spontaneity is not relevant on a soteriological path in other traditions or practices?
From the 8th century (Kamalashila), Tibet sought to go back to the source (Indian Buddhism, not Chinese or Korean) but it took them centuries. In the 10th century, Atisa was summoned from India to Tibet to help revive Buddhism after it has been persecuted. Before even reaching Tibet, he sent the Tibetans the very first Lam rim. Lam rim is a textual genre that means: gradual path. The cultivation became a matter of expedients applied more or less forcefully. It is not about simply seeing one's own nature, but carving oneself.
In addition, where Zen generally focuses on the effortless aspect of the mind of a buddha, Tibetan traditions focus on the omniscient aspect of the mind of a buddha. Omniscience is often not posited, and sometimes not accepted, by Zen masters. Sam van Schaik wrote a valuable book on the topic Tibetan Zen: Discovering a Lost Tradition.
The Huayan tradition also focused on omniscience rather than naturalness; on expedient means rather than sudden teachings.
The Pure Land tradition was far away from spontaneity, since they though the practitioner was unable to reach enlightenment by its own power. In
Traditions of Meditation in Chinese Buddhism, there is a chapter on the topic. It is called From Dispute to Dual Cultivation: Pure Land Responses to Chan Critics by David W. Chappell.

Thank you for the answer (and the references). Could you add a sentence, to explain why it's "not relevant on a soteriological path in other traditions or practices" (e.g. by saying what instead is more relevant in those)? Also fwiw I can't say I remember something like that in the Analects: I dimly remember that as being all about study, e.g. learning the classics so that you have something (appropriate) to play at all.

@ChrisW done. Also, in Slingerland's book, there is a chapter "The paradox of Wu-wei in the Analects". Right from the starts, he says "Confucius places a great deal of emphasis upon the importance of "naturalness" in the moral life."

Hard to say without chinese signs roryo, seems to be 'faraway'.

(In my personal understanding, based on study and practice:)
"What would they mean by "intense discipline" ...?"
This refers to your standard Buddhist training, sila/prajna/samadhi - the paramitas, the minimalism, the discipline of the mind, the tranquility, the egolessness etc. The idea is that "a gorilla" can't be spontaneous until it learns how to behave itself. It has to acquire some real skill before it can relax and let go.
"More centrally, to this question, what is the role of "spontaneity"? Is it a goal? A means to the goal? A side-effect or symptom of having reached "the goal"?
As I understand, spontaneity is an "internal" aspect of Liberation, while Suchness is an "external" aspect of Liberation. When one has fixed one's coarse karmic issues (primarily in terms of one's personal situation and livelihood), has no mental obscurations (illusions, reifications), and no emotional obscurations (active neuroses, attachments) - then one has no conflict with the world, every moment is subjectively perceived as "right" or "such" - everything is just so. This is cessation of dukkha with regards to the world. Similarly, because one has no inner conflict, the discipline being completely integrated, and no illusion of self, one's own activity is subjectively perceived as effortless and full of certainty - i.e. lacking any sense of inner resistance. This is cessation of dukkha with regards to self.
"Is spontaneity practised somehow, or is that a paradox?""
It is generally understood that the lack of remorse due to accomplished ethics, realization of selflessness through practice of murdering Ego's defense, altruistic compassion to others, right meditation, simple living conditions, direct experiential realization of Emptiness, and a certain amount of sleep deprivation - together lead to spontaneity. Also, different teachers have different means of inducing it, e.g. my Zen Master arranged for someone to suddenly blow a vuvuzela in the middle of meditation session. Tibetan masters are known to shout "Phat" with the same intent. Much of Zen anecdotes and some of Tibetan folklore (e.g. Life of Marpa, Life of Milarepa) are full of stories about teachers pulling the rational ground from under the student's feet.
"Is there famous (written and translated) Zen doctrine on the subject ... an explanation by someone?"
I don't know of any. In my experience, Zen masters are not fond of conceptual elaboration. They tend to demonstrate more than explain, or if they do explain they do so in extremely pithy form, that most of the time can't be carried outside of the immediate context.
"Does it (or something like it) exist, as a value or as a goal or whatever it is, in other schools of Buddhism (e.g. Theravada, or ...)?"
There is plenty of texts about this in Tibetan tradition, especially in Dzogchen which is considered by some to be a cousin of Zen. Reference Tögal.
In Pali Canon, supposedly suchness&spontaneity are implied as the culmination of those typical sequences of Jhana that go from coarser to finer, until the student realizes that "even this state is conditioned" - and then follows Release. See for example Cula-suññata Sutta:

He discerns that 'This theme-less concentration of awareness is [still] fabricated & mentally fashioned.' And he discerns that 'Whatever is fabricated & mentally fashioned is inconstant & subject to cessation.' For him — thus knowing, thus seeing — the mind is released [...]

"Is it spontaneity but within some limits? For example, within the limits of "ethical rules" ... or within the limits of, I don't know, calligraphic and/or other arts, for example?"
It is spontaneous manifestation of fully-realized wisdom and compassion - so naturally it represents the very essence of Sat-Dharma that we typically attempt to capture with the ethical rules.
"Assuming it's a well-known concept, is "spontaneity" the right word, the right translation for it? What could be other translations? What's the original (pre-translated) word or words?"
I've seen this referred to as "finding one's true nature", "realization", and even just "zen" as in "show me your zen". Not sure what the Pali Canon level word is though. Perhaps "freedom/liberation/release" and "certainty"?

Case 5 of the Mumonkam  Kyogen Mounts the Tree
Kyogen said: "Zen is like a man hanging in a tree by his teeth over a
  precipice. His hands grasp no branch, his feet rest on no limb, and
  under the tree another person asks him: 'Why did Bodhidharma come to
  China from India?'
"If the man in the tree does not answer, he fails; and if he does
  answer, he falls and loses his life. Now what shall he do?"
Mumon's comment: In such a predicament the most talented eloquence is
  of no use. If you have memorized all the sutras, you cannot use them.
  When you can give the right answer, even though your past road was one
  of death, you open up a new road of life. But if you cannot answer,
  you should live ages hence and ask the future Buddha, Maitreya.
Kyogen is truly a fool Spreading that ego-killing poison That
  closes his pupils' mouths And lets their tears stream from their
  dead eyes.

I remember one sesshin that I went to.  My instructor was recounting the story of a student, who, having been given this koan, showed up to dokusan room, took off all of his clothes, and sat down across from his roshi.  That roshi, not missing a beat, rang his little hand bell signaling that the interview was over.
"What!?" the student exclaimed, "This koan is about spontaneity!  How can you get anymore spontaneous than stripping naked???"  The roshi smiled, started meowing like a cat, and rang the bell a second time.
Zen spontaneity is not a mysterious thing.  At least, not when you've been gazing into emptiness (or mushin) for any extended period of time (that's your vigorous practice, btw).  In fact, this relationship between deep engagement with emptiness and spontaneity is at the very heart of the work we do with koans.  Our small mind is tirelessly verbal.  It give us explanations for everything.  It plans.  It makes excuses.  When we look into mushin, we first put aside that smaller mind.  We must make ourselves free from the burdensome practice of judging.  The rest of the process is watching and waiting to see what comes up.  Sometimes what we find makes sense; sometimes it doesn't.  Sometimes what we see is related to our koan and sometimes it isn't.  No matter what we find, it's important to remember that these things are just appearances.  They miss the source.  The source is what we're after.  It's where all spontaneity comes from.
That student?  He knew what he was going to do before he ever showed up into the dokusan room.  That roshi?  Before his big mind told him to make the sound of a cat (which was really the lion's roar of the true dharma), the thought never occurred to him.  Had he lifted his leg and peed on that student, made him tea, or cut off his own head, he would have been no more right or wrong.

This koan always helped me with the 'goal'.

Luoshan asked Yantou, "When arising and vanishing go on unceasingly,
  what then?"
Yantou shouted and said, "Whose arising and vanishing is it?"

It is the dichotomy that makes 'difficult' from 'easy' and 'goals' from the void. Maybe it is less about where you're from or going, and more about where 'you' are. But hey, what do I truly know.
Basically, keep it up!


text:
How to reconcile non-attachment in a Type-A, North American culture where work is life?
I've been meditating on-and-off for years.
However, the non-attachment preached by the Buddha conflicts with the environment around me. I'm in a large urban center in North America.
Achievement is valued; I feel like I'm contributing to the world in a small way.
I feel like it makes me better at my job to dream big and get attached to goals big and small, whether it's mentoring someone junior or committing years to a project that has an uncertain payoff.
This puts me at odds with my meditation practice, where "letting go" is emphasized.
The best resource I have found specifically addressing this question is Stephen Batchelor's book "After Buddhism". In it, Batchelor lays out one possible interpretation of the scriptures, in which the Buddha and his disciples are very much 'in the world'---businesspeople, merchants, town doctors, etc.---this was refreshing to read and made me feel more at ease.
Am I asking to eat my cake too? I value Buddhism and meditation, but I also value my Western individualist roots and feel egoistic achievement is necessary for progress in science and technology.
Thank you!

Firstly, I am very much against this pop-culture Buddhism where too much emphasis is given to letting go and not that much emphasis on Bhavana and development of wholesome qualities. Letting go of what, exactly? Definitely, check out Thanissaro Bhikkhu's talks on YouTube who shares a similar opinion. There are many things which we need to let go: anger, jealousy, rage, covetousness, stinginess, delusion etc. There are many things we need to develop or "acquire": Metta, Compassion, Euqanimity, Mindfulness, Patience, Humility, Wisdom etc. Knowing which qualities are wholesome and developing them and which are unwholesome and letting go of them is practical wisdom.
Why does achievement need to be egoistic? Why not process and vision driven? We can always frame "achievements" as something bringing long term happiness to ourselves and the people around us instead of something "I" have added to my shining Resume. If that is the case, then no need to hesitate in pouring our energies into it; unless you realise later that this is not really the case.
A very interesting Theravada list is the four Iddhipada (four bases of mental power) cultivated for success in spiritual practice but equally applies in lay achievements. They are Chanda (Desire or Aspiration), Viriya (Energy), Citta (Keeping the Goal in mind), Vimansa (Review or Investigation of results to adjust). So, the Buddha is not against being competent, efficient and energetic in achieving your goals. Quite the opposite, he encourages it.
Also, don't worry about ego too much. Even third path Anagamis have conceit. It is a very deep fetter. So, don't be too worried about it as long as you are aware of it. Even, Ananda the Buddha's attendant once mentioned that we use conceit to overcome conceit (for example to be regular in practice), and moderation in eating to overcome sense desire. Otherwise, you would be going to the extreme of self mortification, which is ignoble and of little benefit.
Hope, this helps.

You will have to be very distinct whether your attachment is towards:
1. Your positive influence to the world;
2. Your reward, no matter big or small;
3. Your egotistic sense of success; and/or
4. Your self/improvement, enlightenment, etc.
If you are towards 1-3, you are not achieving enlightenment.
If you feel you are towards 4 but you are not reducing any suffering, you are not achieving enlightenment either.
Remember, enlightenment is not just about letting go, but void of suffering. Are you following the 4 noble truths? and the 8 folds paths in what you do?
And by the way, egoistic achievement is NOT necessary for progress in science and technology. You can say it is a motivation for some people, but it is not the only possible motivation. Therefore, the "individualistic roots" are neither permanent nor necessary.

Here is Acharya Nagarjuna's advice:

.... Don’t have as objects of your
  mind the eight transitory things of the world: namely, material gain
  and no gain, happiness and unhappiness, things nice to hear and not
  nice to hear, or praise and scorn. Be indifferent (toward them).

Your question strikes me as wondering if it is possible to make progress towards liberation while maintaining the same level of attachment to the Eight Worldly Concerns. I'm afraid the answer is no. What are the eight worldly concerns?

Hoping for material gain (money, things, materialism)
Fear of material loss (not wanting to lose your stuff)
Striving for worldly happiness (many forms, but all temporary and ultimately unsatisfactory...)
Fear of wordly unhappiness (not getting what we want in terms of above...)
Desiring people to say nice things (aka, how awesome we are)
Aversion to receiving criticism from others (how dare they!)
Wanting others to like us (our reputation is so important)
Fear that others won't like like us (being shunned)

Can progress be made toward liberation without requisite decline of the hold these concerns have on us? Here is what Lama Zopa Rinpoche has to say:

It is very easy to do Dharma activities such as reciting mantras,
  saying prayers, making offerings and things like that with the thought
  of the eight worldly dharmas. That happens. But in reality, the holy
  Dharma, which includes all these activities, actually means renouncing
  this life. Therefore holy Dharma and worldly dharma can never be done
  together. Nobody can do these two things—renounce this life and seek
  the happiness of this life with the eight worldly dharmas—at once. We
  can do one and then the other but never both together in the one mind
  at the same time.

Emphasis mine. Merely becoming aware of the eight worldly concerns and familiarizing with the idea that these are hindrances to be overcome is itself some progress. Which is to say that one mustn't completely eliminate attachment towards these concerns before one can start to make any progress! Rather, you shouldn't fool yourself into believing that progress can be made while ignoring these hindrances or worse thinking these hindrances aren't in fact hindrances.
Making progress in eliminating attachment to these worldly concerns is concomitant with making progress towards liberation.
It is a hard answer, but hopefully worth considering.

However, the non-attachment preached by the Buddha conflicts with the environment around me. I'm in a large urban center in North America.

In North America & in the West, some people even treat Buddhism itself (and teaching Buddhism) as a business (for making money). I would suggest to not take to heart everything you might hear and read, because the heart of Buddhism is beyond the reach of the average person.

Achievement is valued; I feel like I'm contributing to the world in a small way.

Worldly achievement is required to earn a living or livelihood.

I feel like it makes me better at my job to dream big and get attached to goals big and small, whether it's mentoring someone junior
  or committing years to a project that has an uncertain payoff.

Sure. The attitude above shows why you should not allow Buddhist theory to confuse your ordinary & natural thinking processes. Buddhism used inappropriately in the wrong contexts may lead to confusion. It is best for us to avoid getting confused & illogical. This also leads to not harming Buddhism.

This puts me at odds with my meditation practice, where "letting go" is emphasized.

Buddhist meditation is for ending suffering rather than for achieving worldly goals.

The best resource I have found specifically addressing this question is Stephen Batchelor's book "After Buddhism". In it, Batchelor lays
  out one possible interpretation of the scriptures, in which the Buddha
  and his disciples are very much 'in the world'---businesspeople,
  merchants, town doctors, etc.---this was refreshing to read and made
  me feel more at ease.

Stephen Batchelor is I think an example of what I described above; of trying to commercialise "Buddhism" in a way which harms the Buddhist teachings, by attempting to make Buddhism relevant for people that Buddhism is not actually relevant for.

Am I asking to eat my cake too? I value Buddhism and meditation, but I also value my Western individualist roots and feel egoistic
  achievement is necessary for progress in science and technology.

I would suggest to simply give up any trendy aspects of your interest in Buddhism, including that book of Stephen Batchelor's.
For example, if scientists find a cure for AIDS or Cancer, there will be a great celebration in society. It will become the most trendy news. However, if this occurs, this does not mean you should take the AIDS or Cancer medicine cure if you do not have AIDS or Cancer.

Thanks for your comment–I understand you disagree with Stephen Batchelor's book, and similar "Western Buddhist" thought.
Do you have a resource or recommendation where I might learn what you find valuable in Buddhist thought? Of a better framework for thinking about these kinds of things?
My interest in Buddhism has been valuable personally and to those around me, so I'd love to hear more about your perspective before giving up my interest :)

Buddhism has teachings for laypeople and teachings for monks. The teachings for laypeople do not revolve around "non-attachment" or four noble truths. Therefore, it is not necessary to pervert the teachings of non-atachment, four noble truths, etc, so they somehow suit lay people. This link summaries the teachings for laypeople from the Pali suttas: https://www.mahidol.ac.th/budsir/Contents.html

Voted down for the ad-hominem attacking on Stephen Batchelor and the general disparagement of entire sangha jewel in the West. At a minimum, the answer should be clarified to use less absolute language regarding the motivation of Buddhists in the West and the ad-hominem on Stephen Batchelor.

I edited this to try to make it less disrespectful by making it more specific. For example the previous version could be read as disparaging all Buddhists and Buddhism in general, everyone and everywhere in America and in the West, whereas I think you want to warn against a more specific phenomenon (i.e. commercialising it, and altering it towards a different audience and purpose).

@lifer You might like this book, too. It too starts by observing that some suttas are intended for lay people, and it organises and summarises the (bookful of good) advice in these suttas about the lay life: including business and money and partnerships and so on.

@ChrisW thanks. The language is less all encompassing. However, I think the parts critical of Batchelor are unwarranted and harmful. The OP posted he found something Stephen Batchelor said as useful to his mind. The language in this answer was made to disabuse the OP from relying upon Batchelor by criticizing him outside of the specific ideas that the OP found useful. If the answerer disagrees with the ideas that the OP said he found useful, then the answer should be edited to find fault with those ideas and not Batchelor. Otherwise, all mention of Batchelor should be dropped.

I thought that the criticism of Batchelor was: on-topic (relevant to the question); specific (not just "it's bad" but "it's commercialising and adapting"); criticising the person's work[s] more than the person; and relevant to the overall thesis (that the OP would get better advice, that the advice would be more Buddhist, if the advice were based more closely on the suttas). Maybe I'm becoming over-inured to rudeness? But it seems to be normal for Dhammadhatu's answer to disagree somewhat with the interpretation of a published author or translator. You're not required to agree with the answer.

I have many disagreements with Batchelor.  However, the OP has said in his question that Batchelor’s book was helpful to him and gave a synopsis of what he found helpful, e.g, that lay folks can feel free to participate in the world etc., what’s more this answeer seems to agree with that message! The big difference is the answerer apparently doesn’t believe Batchelor is a good messenger. That’s highly problematic and potentially harmful wrong speech. If the answerer has a problem with the message, then spell it out. That is apparently not the case. @ChrisW

I am very wary of and sensitive to people trying to disabuse others of reliance on their teachers. It is disrespectful and arrogant at best and actively harmful at worst. Leads to bad feelings and can turn people away from what they have found helpful. Like you said in another comment, there are many paths and teachings for everybody and to claim monopoly is arrogant. Now, if people espouse certain viewpoints, ideas, doctrines that people disagree with them then please feel free to spell out the disagreements! But questioning authenticity of people the OP has said they find helpful is too far.

The only thing that makes Batchelor relevant here is the view that some Suttas can be interpreted as agreeing that, “the Buddha and his disciples are very much 'in the world'---businesspeople, merchants, town doctors, etc.” if dhammadatu disagrees with this message, then he can say so and provide alternative view with reasons. That would be very much relevant to answering the question. Not trying to pour water on Batchelor as valid teacher while leaving the message unaddressed.

@Yeshe, you're technically right, but over the last few years we kinda noticed it works best to be somewhat tolerant to intolerance. Meaning, it's good to stop someone when they are being a total ass, but sometimes it's almost better to leave it be, especially when it comes to people's opinions on what is right dharma /  wrong dharma, you know? I value your participation, but let's try and make sure our efforts toward reducing conflict are not inadvertently increasing it, if you know what I mean... I think Chris softened the language enough for it to be a passable opinion. Let's move on?

I'm going to let this sit for awhile and think about it. To me this goes to a question of whether site moderators should correct harmful speech when it is flagged. I personally would like to have it pointed out if/when I am speaking harmfully and given a chance to correct. Moreover, if I'm incapable of seeing the harm my speech does I'd consider it a kindness for others to prevent that harm or help mitigate it by removing it. I have personally witnessed the harm that criticizing teachers (even if seemingly warranted) can have on a student of that teacher and lead away from Dharma @AndreiVolkov

Fair enough. Let's let it marinate.

In my opinion, it is totally reconcilable. Not just "reconcilable", Buddhism is the best part of Type-A attitude taken to its logical conclusion.
If you think about it, Siddhartha himself used to be a typical Type-A person: highly ambitious, driven to success, unhappy with status-quo.
In my opinion, the more a Type A person optimizes his or her behavior to achieve their own definition of success, the more they will look like an enlightened Buddhist. And vice versa, the more a Buddhist realizes the teaching in practice, the more they will behave like a (purified, enlightened version of) a good business leader - strong, happy, confident.
Per my live teachers, non-attachment in Buddhism IS NOT cultivation of meekness. It is cultivation of unsinkable optimism and wise flexibility of mind.
(Mahayana) Buddhism is not against achievements either, it just offers the ultimate, more meaningful Achievement for those who are up to the challenge. My teacher said, this world is a perfect gym to train our Enlightened Mind qualities, so take it as such.
Buddhism may be at odds with small-minded, egoistic, fearful, greedy, aggressive attitude of some people - but these attitudes are not approved by the modern civil society either. So we are in complete sync with the spirit of times, I think - and should not be afraid to expose our Buddhist values to the public. IMO to be an open Buddhist would be  beneficial for society these days.

I think this is a good answer. To my mind it seems entirely consistent with avoiding the eight worldly concerns. For instance, how can one generate true confidence while worrying about reputation or trying to avoid criticism?