I wouldn't be surprised if there has been another thread about it, and I've discussed the topic a little in other threads before, but I'd like to hear more about it:

What do you think the Buddha meant with this and why:

"[1] Breathing in long, he discerns, 'I am breathing in long'; or breathing out long, he discerns, 'I am breathing out long.' [2] Or breathing in short, he discerns, 'I am breathing in short'; or breathing out short, he discerns, 'I am breathing out short.' [3] He trains himself, 'I will breathe in sensitive to the entire body.' He trains himself, 'I will breathe out sensitive to the entire body.' [4] He trains himself, 'I will breathe in calming bodily fabrication.' He trains himself, 'I will breathe out calming bodily fabrication.'

Do you think it is supposed to be practiced in steps, like most teachers seem to interpret it, or all at once? I mean, its not like the Buddhas put the numbers there when he gave the discourse, is it?

And do you think the body means entire physical body or breath body? There are valid arguments for both:

Physical body: bodily fabrications is mentioned directly afterwards, and according to the Culavedalla sutta, bodily fabrication means the breath. Why would the Buddha throw around different expressions meaning the same thing (breath, (body of) breath, bodily fabrication)? Also, if one isn't aware of the entire physical body, one can't be sure whether one is really filling the physical body with the jhana factors, which one should do according to a lot of suttas, the Kayagatasati sutta for example.

Breath body:
Much later in the sutta, the Buddha says
:"I tell you, monks, that this — the in-&-out breath — is classed as a body among bodies"

If entire body means breath body, then what does breath body mean? Entire breath?

If you've tried both approaches: do they lead to different results and/or different kinds of jhana?

Buddhadasa Bhikkhu has explained this correctly, here: http://www.dhammatalks.net/Books3/Bhikkhu_Buddhadasa_Anapanasati_Mindfulness_with_Breathing.htm

1. Kaya sankhara means 'body fabricator' rather than 'body fabrication'. Read MN 44 more thoroughly, where it states applied & sustained tthought are the verbal fabricator because 1st one thinks and 2nd one breaks out in speech. Similarly, the state of the breathing is the cause for the state of the physical body. The term 'fabricator' infers a 'cause' where as the term 'fabrication' infers an 'effect' or 'end product'.

2. We must keep in mind the purpose of practise, which is to understand the 4 noble truths. Each of the last 14 stages begins with the phrase: "He trains himself". This means at each of the 14 stages, there is full realisation of the three trainings, namely, morality, concentration & wisdom. Therefore, at stage 3, the enlightenment realisation must occur of: 'When the mind is like this, the breathing becomes like this; when the breathing becomes like this, the body becomes like this, when breath & body are like this, the mind feels like this'. In other words, it must be clearly discerned when the mind is free from craving, attachment & judgments, the breath calms.When the breath calms, the body calms, when calmness occurs, this is peace, this is Nibbana. This cause & effect relationship, between the mind, breath & body, must be seen clearly (vipassana) for the 3rd stage to be complete. When this cause & effect relationship (the 4 noble truths) is seen clearly, the three trainings of morality, concentration & wisdom are fulfilled. This is why Buddhadasa is correct when translated the term "sabba kaya" as "all bodies" (rather than the 'whole body'). The Pali word 'sabba' means 'all' (such as in the phrases 'may all being be happy' & 'all conditioned things are impermanent'). The Pali word for 'whole' is 'kevala' rather than 'sabba'. Thus, the Buddha said: "I tell you monks, the breath is classed as a body among bodies'. The word 'kaya' can be limitted or broad. The word 'kaya' means 'collection' and often refers to the five aggregates (such as in the term 'sakkaya ditthi'). At step 3, the Pali is 'all bodies', which means the breath body & the physical body (and also the mental body - nama kaya).

3. The 4 tetrads are practised in stages however the steps within are often practised together. For example, steps 1 & 2 are practised together, since the length of the breath will vary naturally. Once samadhi is correct, then step 3 will occur. Here, the length of the breath is discerned, the same as stages 1 & 2, but also how the different breathes effect the body is also discerned. Then when the mind discerns 'making the mind let go' calms the breathing, step 4 occurs. So in perfect practise of the 1st tetrad, all 4 steps will eventually occur together.

3a. Tetrad 1 must be completed before Tetrad 2 can occur, since the cause of Tetrad 2 occuring is the calming of the breathing until it can only be discerned (naturally) in the nose tip area. This one-pointed samadhi should occur naturally (rather than forced), otherwise the rapture may be difficult to control & the mind will not be detached enough for insight to occur.

4. In tetrad 2, step 5 must pass before step 6 occurs. In other words, rapture must calm before happiness is discerned. The 7th step is the same as the 3rd step. Here, it is discerned rapture & happiness are the mind conditioner or fabricator. Thus this must occur with the 5th and 6th steps. The 8th stage is a little different because it discerns how to calm rapture & happiness (which is merely via letting go & also dispassion towards them). At this stage, if samadhi is correct, the mind should already have discerned Nibbana & thus realised rapture & happiness are coarse & disturbing in comparison to the peace of letting go & purity/equinimity of mind (Nibbana). Thus the attitude of non-attachment & non-craving will calm rapture & happiness. Rapture & happiness are the mind conditioners (rather than the 'mental fabrication').

5. Tetrad 3 is generally a mystery because few reach it. Tetrad 3 occurs when rapture & happiness calm and underlying mental defilements (not thoughts) become the objects of meditation and then are progressively cleansed. Tetrad 3 is extremely profound and unimaginable to those that have not reached it.

6. The Buddha taught 'letting go leads to jhana' (refer to SN 48.9 & 10). The entire practise from the start is 'letting go'. The 16 steps, incuding jhana, are mere sign posts. They are merely the scenery rather than the journey itself. It is not necessary to make a deliberate effort to observe the breathing. When the mind lets go, in that stillness & clarity of mind, the breathing will naturally become the object of the mnd.

7. Anyway, that is my take on it. I trust others have different opinions, such as feeling their little toe is experiencing the entire body.

8. Also, there are two levels of enlightened samadhi: (i) neighbourhood concentration & (ii) attainment (jhana) concentration. Therefore, reaching the 2nd tetrad does not necessarily mean jhana has occured. Jhana occurs when the mind is ekkagatta.

As I posted, the Buddha is not throwing anything around. The term 'sankhara' in the context of MN 44 means 'fabricator' rather than 'fabrication'. If you don't believe me & remain stuck on Thanisarro's mistranslation, then refer to Thanissaro's work: 'The Shape of Suffering', at the link, pages 3 to 6, where he psycho-physiologically describes these terms exactly as I have (despite keeping the mistranslations):  

http://www.accesstoinsight.org/lib/authors/thanissaro/shapeofsuffering.pdf

To reiterate: the breathing is the body fabricator because it conditions the state of the physical body. Not only is the breathing necesssary for the life of the physical body but the quality of the breathing will affect the quality & health of the physical body. Similarly, applied & sustained thought (vitakka & vicara) are the verbal conditioner because thought conditions speech. Similarly, perception & feeling are the mind conditioner because they condition the emotions, defilements & thoughts of the mind. For example, a pleasant feeling & perception of 'beauty' will condition defilements & thoughts of love, lust, greed, etc.

As for the Kayagatasati Sutta (despite the Buddha probably not actually speaking it), when it states: "he saturates his whole body with rapture", this does not necessarily mean the mind is aware of the rapture within the physical body. An analogy is watering soil. One is only aware of the water at the surface, coming from the hose, despite the soil underneath being saturated with water.

When the 1st jhana is approached, the nerves in the physical body will start exploding with rapture. The mind will be aware of this. However, when the 1st jhana is actually entered, there will no longer be awareness of the physical body (despite the nervous system being saturated with rapture). In the 1st jhana, the mind is only aware of the rapture in the brain (despite the entire nervous system being saturated with rapture).

Thanks for that great explanation! 
I don't agree at all with the last point though. Ekagatta comes in the secong jhana, it says in like all suttas except mn 111 but that's a lately written one.

How do you mean that the 3rd step occurs naturally after 1 and 2? If I'm aware of the breaths length for long enough time, will my attention automatically spread across the whole physical, mental and breath body? Or can one be at step three while being aware of some of the physical, some of the mental and some of the breath body? 
I thought Buddhadasa was a visuddhimagga guy who taught nose attention and nimittas and stuff like that, not mentioned in the suttas. But this explanation is great.

If one can't feel the body while in the jhanas, how can one kniw one is breathing in and out? If we can't know that, it's not really anapanasati, is it? And in all of the tetrads one trains oneself to do stuff while breathing in and out, there must be someway I can know if I'm breathing or not, right?

Ekagatta comes with the 1st jhana, as the scriptures explain. You are confused about the Pali.

The term in the 2nd jhana is not ekaggata.

By the way, from your point of view, can and should one practice the instructions from the Vitakkasanthana sutta at the same time that one is practicing the instructions fron the Anapanasati sutta?

That could be the case. Which sutta is that from? 

It is a stock phrase in every sutta that explains the jhanas & three knowledges. MN 4, MN 19, etc.

Yes you're right I'm confused about it. The thing is, i thought ekaggatta and ekodibhavam was synonymous -what's the dufference? And the thing before that with ekagatta I haven't seen much.

Excellent point but I already pre-empted this, when I posted:

This leads to the speculation that MN 118 is on the level of neighbourhood concentration since every step is done with awareness of breathing (where as in the 1st jhana, awareness of breathing ceases, due to ekkagatta).

Yes. When meditation begins, when samadhi is coarse, it initially discerns the length of breathing (steps 1 & 2). But as samadhi improves and becomes more receptive, it feels the quality of the breathing (smooth, rough, etc) and how the quality of the breathing influences the feeling of the body (relaxed, stressed, etc). This is step 3. Then it will discern how the state of mind affects the breathing, particularly the progressive calming of the breathing (step 4).

Buddhaghosa is the Indian Brahmin Visuddhimagga guy. Buddhadasa is the modern Thai guy (1906 – 1993)

I would say practise MN 20 only when necessary. Once MN 118 is established, there will not be distracting thoughts. But if distracting thoughts occur, then MN 20 may need to be practised.

It depends on how strong the thoughts are. If the thoughts can be eradicated by using breathing then eradicate them, like using a vaccuum cleaner.

The whole goal of MN 118 is to realise the peace, happiness & freedom of the samadhi mind.  

Are there any other suttas that say one can't feel the body or the breath while in first jhana? I've only seen descriptions where the perception of the physical body ceases at fifth "jhana" (only the first four are called jhana in the suttas as far as I know). I've never seen anything about neighbourhood samadhi in the suttas eihter.

Wait if you meant yes to the first paragraph, then entire body isn't a completely incorrect translation?
Yes I know the difference between Buddhadasa and Buddhaghosa, but I thought Buddhadasa's teachings where from the visuddhimagga.

Ok, so if bringing the mind back directly to the  breath doesn't work then I do mn20? I thought that one should do both at once since I don't know any other sutta on handling distractions. And according to Thanissaro, the first step of mn20 is the same as bringing the mind back to the object, although I think that sounds a little far fetched.

The suttas say the 1st jhana has 5 factors, which are all mental.

As for neighbourhood concentration, yes, no mention in the suttas.

However, many hard-core non-conventional non-Commentarial meditators attest to this from actual experience.

There are 16 stages of Anapanasati that can be practised prior to jhana.  

I would suggest to carefully read Buddhadasa's explanation of "all bodies" in the link i posted to see if it makes practical sense to you.

"All bodies" means there are more than one body and the cause & effect relationship between those bodies is to be discerned.

For example, when the breathing is calm, smooth & long, the physical body relaxes & the mind is calm.

This has a spiritual meaning (rather than a concentration meaning).

The point of Buddhism is not about concentrating. It is about understanding the causes of peace in life.

Regards

MN 19 is also about handling distractions. MN 117 is also good. Kind regards.

Thanks! I've read mn 19 before, it seems like in that one, the Buddha jumps directly to the second step in handling distractions as it is taught in mn 20. Why does the Buddha teach in mn 20 that the five methods should be done in a certain order, when he skips it himself? Or does he?

That sounds awesome actually, and much easier than awareness of the entire physical body. Sounds a little like Vimalaramsi's statement that jhanas are levels of understamding rather than levels of concentration. So step 3 is more like awareness of a relationship rather than awareness that includes the entire masses of each body?