The way feelings behave is to arise, take a stance, and disband. That's all there is to them every time. And there's no 'being,' 'person,' 'our self,' or another to them at all. As soon as we invest them with the ideas of 'being' or 'person,' they will appear in terms of beings and persons, which are the powers giving rise to the cause of stress in that moment, and we'll immediately be intensifying stress. Meditators should thus use their discernment to be circumspect in dealing with feelings. If you don't take feelings to be yourself while you are investigating them, all three sorts of feelings will appear clearly as they truly are in line with the principles of the frames of reference and the Noble Truths. No matter how these feelings may change for good or bad, it will be a means of fostering the discernment of the person investigating them each moment they exhibit movement and change. The notions of 'being,' 'person,' 'our self,' or 'another' won't have an opening by which to slip into these three sorts of feelings at all. There will be just what appears there: feelings as nothing but feelings. No sense of sorrow, discontent, discouragement, infatuation, or pride will be able to arise in any way while these three sorts of feelings are displaying their behavior, because we have come to a proper understanding of them -- and all the time that we as meditators have a proper understanding of feelings while they are arising, we are said to have the contemplation of feelings as a frame of reference in the heart.
The mind as a frame of reference is not a level of mind different or apart from the other three frames of reference, which is why it is termed a frame of reference just like the body, feelings, and phenomena. If we were to make a comparison with timber, the mind on this level is like an entire tree, complete with branches, bark, softwood, roots, and rootlets, which is different from the timber put to use to the point where it has become a house. To contemplate the mind as a frame of reference is thus like taking a tree and cutting it up into timber as you want. To investigate the mind on this level, we should focus on the thought-formations of the mind as the target or topic of our investigation, because these are the important factors that will enable us to know the defilement or radiance of the mind. If we don't know them, then even if the mind suffers defilement and stress all day long, we won't have any way of knowing. If we want to know the mind, we must first understand the thought-formations that condition the mind in the same way that seasonings give various flavors to food. The fact that the mind displays such an infinite variety of forms, becoming so changed from its original state as to bewilder itself, not knowing the reason and how to cure it, giving in to events with no sense of good or evil, right or wrong, is all because of the thought-formations that condition it.
For this reason, the mind as a frame of reference is a mind entangled with its preoccupations and conditioned by its thought-formations. The investigation of thought-formations is thus related to the mind, because they are things interrelated by their very nature. If we understand thought-formations, we will begin to understand the mind, and if we understand the mind, we will understand more about thought-formations -- starting with thought-formations from the blatant to the intermediate and subtle levels, and the mind from the blatant to the intermediate and subtle levels. These levels of thought-formations and the mind come from the fact that the mind can become involved with blatant, intermediate, or subtle preoccupations. People contemplating the mind as a frame of reference should thus make themselves understand from the very outset that the mind and its conditions, or thought-formations, are two different sorts of things. They aren't one and the same. Otherwise the mind and its thought-formations will become entangled and this will complicate the investigation as I have already explained.
The point to focus on is the arising and involvement of thought-formations -- what preoccupations they touch on -- as well as their disbanding together with the disbanding of their preoccupations. Try to observe and keep track of the movements of these thought-formations that come out from the mind to focus on preoccupations of the past or future, both blatant and subtle. Always be aware that thought-formations and preoccupations of every sort that are interrelated must arise and disband together. They can't be made to behave otherwise. Thus the notions of 'being,' 'person,' 'self,' or 'other' shouldn't be brought in to refer to the mind, because they will immediately turn into a cause of stress. Try to observe until you see this in the course of the investigation, and you will see, as the Buddha taught, that the mind is simply a mind and nothing else -- not a being, a person, self, other, or whatever. When we contemplate the mind in this way, the heart will not be upset or infatuated with the fashionings and conditions, the pleasures and pains of the mind. This is what it means to have the mind as a frame of reference.
'Phenomena' (dhamma) as a frame of reference covers anything that serves as a focal point of the heart. On the refined level, it refers to the heart itself. External phenomena are of many kinds. Internal phenomena include every part of the body, all three kinds of feelings, and the mind on the level of a frame of reference. All of this is included in the contemplation of phenomena as a frame of reference. The contemplation of the body, feelings, and mind together -- all four frames of reference at once -- is, from the standpoint of forest Dhamma, [*] the contemplation of phenomena as a frame of reference. If this is in any way wrong, due to my lack of skill in understanding and explaining the matter, I ask forgiveness of all my listeners and readers, because I always feel at a loss every time I mention the topic of forest Dhamma in any of my talks or writings. For this reason, I ask that my readers, when reading about forest Dhamma, try to cultivate a fairly open mind toward every passage so that they won't get upset while they are reading.
[*] The Dhamma learned from practice, and not from the study of books.
When, in the course of the investigation, the four frames of reference are brought together in the contemplation of phenomena so that they become a single level of Dhamma, this is a point in the practice more amazing and unexpected than anything that has gone before. This is because in the beginning steps of the investigation the body is like a piece of wood in the raw state. Feelings are in a raw state. The mind is in a raw state. Even phenomena are in a raw state, because the investigation itself is like a piece of wood in the raw state, so that the things investigated are all in the same state. But when we plane and polish things with the effort of the practice, everything in the area of the practice gradually changes its condition.
What I have mentioned here concerning the contemplation of phenomena as a frame of reference is a fairly refined level of Dhamma, so we can't help but be grateful for the groundwork laid during the raw state of the investigation on the beginning levels. When we investigate phenomena in the final stages, if feels very different from the beginning stages, even though they are the same four frames of reference. When we reach the final stages, it appears to the mind that all four frames of reference -- body, feelings, mind, and phenomena -- connect so that they all come under contemplation of phenomena as a frame of reference. They converge completely so that there is no sense that this is the body, that's a feeling, this is the mind, that's a phenomenon. They all seem to come together on a single level of Dhamma.
In dealing with the body, feelings, and mind, I've given a fairly adequate explanation of the methods of investigation for remedying and freeing the mind, but now that we come to the topic of phenomena, the discussion seems to have dealt entirely with my own experiences. Nevertheless, I hope that you will approach it with the attitude I've just mentioned and put it into practice in a way suited to your own temperament. The results are sure to come out directly in line with what I've explained to you.
To summarize the four frames of reference: There is the body, which covers the internal body, external bodies, and the body within the body. There are feelings -- internal feelings, external feelings, and feelings within feelings. (The issue of feelings is fairly complex, so I'd like to insert a few opinions here: Internal feelings are feelings or moods in the mind. External feelings are feelings in the body.) There is the mind -- the inner mind, the outer mind, and the mind within the mind. 'The inner mind' refers to mental states that deal with preoccupations exclusively within the mind. 'The outer mind' refers to mental states involved with external preoccupations. 'The mind within the mind' refers to any single mental current out of the many mental currents that come out of the heart. And then there are phenomena -- inner phenomena, outer phenomena, and phenomena within phenomena. 'Inner phenomena' are the refined states or preoccupations that are objects or focal points of the mind, and also the mind itself, which is the converging point of all mental objects. 'Outer phenomena' refers to every kind of external condition capable of being an object of the mind. 'Phenomena within phenomena' refers to any single condition out of the many conditions that are the focal points of the mind.
Thus the terms 'body within the body', 'feelings within feelings', 'the mind within the mind', and 'phenomena within phenomena' refer to any single part or instance of these things. For example, any one hair out of the many hairs on the head, any one tooth out of the many teeth we have: These are termed the body within the body. A person investigating any one part of the body in general is said to be contemplating the body within the body. The same holds true for feelings, mind, and phenomena, but I won't go into detail on this point for fear that we won't have enough time. Let's save it for a later date.
The four frames of reference, from the point of view of forest Dhamma, are present in full measure in our own bodies and minds. This doesn't mean, though, that their external aspects are irrelevant. This is a point you will see clearly when you work at the frames of reference until you can connect them entirely on the level of contemplation of phenomena. The mind won't feel compelled to search for anything external to help in its practice. Simply investigating exclusively in the area of the body and mind, using the four frames of reference complete in the body and mind, will be enough to cure it of its problems.
On the beginning level, though, everything internal and external is relevant. But as you reach the stage of letting go step by step, those various conditions will lose their relevance. Even the body, feelings, mind, and phenomena, which are the necessary terms of the frames of reference, have to be let go. They shouldn't be held to or borne as a burden on the heart. They must all be let go when your investigation fully reaches the point of dhamma anatta: Phenomena are not-self. Then later you can turn around to contemplate and connect them again as a pastime for the mind in the present, once the mind has gone beyond and yet is still in charge of the khandhas.
Meditators, if they are firm and unflinching in the practice of the frames of reference, are sure to see a variety of extraordinary and amazing things arising at intervals in their minds. When the time comes to reap the results on the level of Dhamma corresponding to the causes that have been properly developed, the results will have to appear stage by stage as the attainment of stream entry, once-returning, non-returning, and arahantship. There is no need to doubt this.
So know that whether we contemplate the four frames of reference or the four Noble Truths, they are one and the same path for the sake of release from suffering and stress. Even though there may be some differences, they differ only in name. In terms of their basic principles, they are one and the same. Those who work at the four frames of reference and those who work at the four Noble Truths are performing the same branch of work, because stress, its cause, its disbanding, and the path to its disbanding are the same level of truth as the body, feelings, mind, and phenomena -- in the same way as when different people do different jobs in a single factory, the profits from their labor all go to the same factory.
To summarize the final results that come from working at the frames of reference and the Noble Truths step by step: In the beginning the body, feelings, mind, and phenomena are in a raw state. Stress, its cause, its disbanding, and the path to its disbanding are in a raw state, because the practice is in a raw state of planing and polishing back and forth without any feel for the heaviness or lightness, depth or shallowness, breadth or narrowness of the Dhamma, and without any sense of right or wrong, good or bad in the practice, because it's something we have never done before. No one, from our great-grandparents down to our parents and other relatives, has ever told us that the frames of reference and Noble Truths are like this or that, that they should be put into practice this or that way so as to give results of this or that sort -- for they themselves had no way of knowing. What's worse, they have taken these excellent frames of reference and Noble Truths and thrown them away underground, underwater and into the fire time and again. We are simply their children, grandchildren, and great-grand-children: How can we boast that we're wise and all-knowing in these matters? We simply have to admit our own ignorance. Even though it's true that the frames of reference and Noble Truths have been excellent Dhamma from the very beginning, when they reach us they have to start as Dhamma in the raw state, because we ourselves are people in the raw state. Even our practice is practice in the raw state. But as we practice persistently, without retreating, and as our understanding into the Dhamma and the practice gradually appears bit by bit, day by day, and slowly begins to take shape, our conviction in the teachings of the Buddha grows continually stronger and more deeply rooted. The things that used to be mysterious gradually come to be revealed for what they truly are.
For example, the four frames of reference and four Noble Truths, even though they were always right with us, used to be as if buried out of sight, without our being aware of them. We listened to monks giving sermons and imagined things to be far away, beyond the range of our ears and eyes. We never thought at all to refer these teachings inwardly to ourselves, the converging points of the Dhamma. When the monks finished their sermons, the results could be summarized as this: 'We don't have the capability of reaching the Dhamma that has been taught, because it's infinitely deep and exceedingly subtle. The Dhamma explained and we the listeners lie on opposite sides of the world.' The thought never occurred to us that all of us -- teachers and listeners alike -- are in the same world of the frames of reference and the four Noble Truths, and that the matters explained were entirely our own affairs without the slightest deviation. These sorts of misunderstandings can happen to all of us.
But when the truth -- such as the frames of reference -- starts revealing itself in the course of our practice, these teachings turn step by step into a map for the mind. We see the body, feelings, mind, and phenomena as if they were a piece of paper covered with symbols and signs showing us the way to proceed so as to gain release from suffering and stress. The frames of reference and Noble Truths, within and without, become symbols and signs showing the way for the mind to proceed on all sides, as if they were saying, 'Hurry up and follow these arrows showing the way to safety. The enemy is in a frenzy searching for you right nearby and is waiting in ambush for you everywhere. Don't be lulled into thinking that any of these places are safe. Only if you hurry through this jungle will you reach safety.' Our persistence in the practice then grows stronger, together with the mindfulness and discernment we have been training by using the frames of reference and Noble Truths as our whetstone and path. The body, feelings, mind, and phenomena that we used to investigate erratically and unevenly now become Dhamma on a common level and can all be investigated so as to be brought together and subsumed under the level of contemplation of pure phenomena.
When the mind takes the contemplation of phenomena as its frame of reference until it is skilled and thoroughly sure of itself, the contemplation of phenomena (dhamma) turns to deal exclusively with the affairs of the mind. At this stage you could say that the Dhamma becomes the mind, or the mind becomes Dhamma. Once the mind has entered purely into the contemplation of phenomena, then external conditions -- sights, sounds, smells, tastes, tactile sensations, and ideas, together with the senses of sight, hearing, smell, taste, feeling, and ideation, which used to be like a solid mountain of rock, obstructing the mind so that it could find no way out -- fade away and vanish from the imagination. The body, feelings, labels, thought-formations, and cognizance that were like clouds obscuring the heart are now dispersed bit by bit from their shapes -- the suppositions of conventional reality -- by the winds of mindfulness, discernment, conviction, and persistence, until they fade away to the point where almost nothing is left. What is left is simply a vapor arising from the heart: This is a level of phenomena that hasn't yet been destroyed but can't display itself openly because strong mindfulness and discernment have it surrounded and are constantly probing after it to destroy it at all times. Finally this level of phenomena -- the mind of unawareness (avijja) -- is utterly destroyed by mindfulness and discernment, using the truth of dhamma anatta -- phenomena are not-self -- and the teaching that all phenomena are unworthy of attachment. The notions of being, person, self, or others, when they no longer have any conventional suppositions in which to find shelter, must now float away of their own accord.

The moment that mindfulness and discernment have completed their duties toward the frames of reference, a nature that is extraordinary and amazing appears in all its fullness. All problems are resolved without any chance of continuation, because cause and effect between the khandhas and the mind have come to a full and lasting truce. Even though they still live together, they no longer quarrel the way they used to. Each is free in line with its truth. The word yatha-bhuta-nana-dassana -- knowledge and vision of things as they are -- in the understanding of forest Dhamma means living with no mistrust between the khandhas and mind, the world and the Dhamma, the inside and the out. The heart and all things everywhere are no longer enemies as they used to be, and the heart can now put all things to their proper uses.