text:
How do you properly practice the more abstract precepts?
The precept of killing is a great baseline. Very clear: if you kill something with intention, you break the precept. The factors I can remember in the kammic disecction of the matter are: the kammic weight of the one being killed, the intention of killing (and any coupling intents), the actual action, whether or not it succeeds, if, any, regret after the action, and maybe a few more factors. Giving each a realistic weight depending on the full situation will give you an average estimate of how bad it is.
The thing is that the actual action is very clear with killing no matter how obscure the situation. With precepts like stealing, lying, or practices like wrong speech there isn't really a meter to hold yourself to. I've asked around on reddit and even here before but I haven't had a proper, well-developed answer to this.
Some answers, particularly for right speech focus on following the heart or judging based on emotions, but that is the opposite of a discerning judgment and many of us follow our subtle judgement to worse kamma, not better.
A meter of 'that which is not freely given' is pretty good but refuted by the sutta that speaks of 'stealing' a flower's smell.
Other answers focus on a middle-ground, but these do not address the right course of action in situations where property becomes non-physical, or ownership of property splits, or other complex situations not faced during the Buddha's time.
At the end of the day, there is definitely a right answer to this question, and it's important to know it for this high-speed age. You need to know this before you find yourself in such a situation because the decision has to be made on the spot. The answer exists because to a Buddha's range, there is an absolute understanding of whether an appropriation of property is stealing or not. This absolute knowledge, assuming it is not the result of direct kammic vision, can be practiced by normal people too.
Edit: For a precept like stealing, ownership is arbitrary and can't be properly defined. Abusive speech is arbitrary and again changes from person to person. What might be a violation of right speech to one person isn't to another. Lying is pretty objective, but also has its' issues in getting proper communication across. In right speech, abusive speech is subjective: some consider certain words abusive, so if you speak to them in such a manner it won't be right speech. Others might not, and then there should be no violation of right speech in that situation even though everything you do is the same. So how do you find that line of practice where you can say, "I am properly keeping this or that precept, without worrying about self corruption?"

I'm not sure this is a question. I don't see any question marks "?" in the text. FWIW the help recommends that, "You should only ask practical, answerable questions based on actual problems that you face".

Do you not understand the question in the title? Or is the issue clarification?
Edit: Adding question to body.

Thanks for the edit. I didn't understand how the precepts, or which precepts, might be "abstract".

Because of the immense depth of the teaching, different skillsets/levels of students, and complexity/multidimensionallity of life in general, Buddhist theory and practice is a set of incremental approximations, from very coarse to more refined and precise. The provisional teachings are formulated in the narrative that makes sense to each particular student, such as the eastern religious narrative, or the narrative of shamanic mysticism, or the narrative of the mainstream society. More advanced teachings make use of the phenomenological narrative, the narrative of the subtle energies, and others. Some of the very advanced teachings require stepping outside of all narratives.
Since all people are different, all operate in different contexts, it is very difficult to make universal statements that mean the same thing to all people, have the motivating/inspiring effect in all the different contexts, and generally lead to positive outcomes in all of the endless "realities" (personal narratives).
The precepts are the lowest common denominator designed to work in all these different worlds. That is, they are meant to be the basic rule of thumb that works well enough regardless of the exact interpretation.
As individual practitioner, your understanding of precepts and of Dharma in general grows and matures - and transforms - during the entire journey. This is known as the transmutation of vows.

On the very basic level, you take precepts as is, without much thinking, and implement whatever they mean to you.
Then, you realize that precepts require you to control your mind and emotions: your "want" and "hate". So your context changes, instead of thinking in terms of external actions you think in terms of your mind states. At this point you don't painstakingly deliberate about individual precepts, you make sure your mind stays sober - as long as you do this, the precepts are "automatically" interpreted and executed in the right way.
Then, you get to the level where you no longer worry about your own goodness. Instead, your concern is about suffering and happiness of others. Just like on the previous level you stopped obsessing over individual precepts, on this level you're no longer obsessed with your mind state. You know, as long as you don't seek personal benefit, don't worry about personal difficulties, as long as you sincerely wish benefit for the others, then your mindstate will be alright, and your precepts will be taken care of.
Then, as you spend some significant time practicing the above, just as you hopefully did with every level (skipping levels in Buddhism is rarely a good idea) your understanding of ethics matures to the point when you understand the relative nature of any reference point. Because you now see that nothing has the absolute truth or the absolute value, you tend to be pretty cool about things, pretty dispassionate. So in your decision-making, you don't cling to any onesided position and you tend to prefer to act in such ways that helps others be less attached to their one-sided positions. So your ethical decisions of do/dont are now guided by your desire to promote wisdom, in-depth analysis, and certainly reduce possibilities of confrontation and conflict due to radicalized opinions, onesided judgements, attachments, and other forms of non-enlightened behavior, because you see that it leads to suffering. Just like the previous levels subsumed and transcended each other, on this level you abandon the notion of "doing good to others" - since good is not something that can be universally defined. So you no longer painstakingly obsess over the calculations of how much goodness will your actions bring to each of the affected participants of your action. Instead, your new rule of thumb is: as long as my actions are expressive of wisdom, promote non-attachment due to wisdom, dispassion due to wisdom - then the net effect will be good in all the different subjective universes.
At this point, you may realize that your personal karma limits your ability to be an expression of wisdom, and under direction of qualified teacher you decide to undertake Vajrayana deity generation practice or one of the other advanced practices. Because your understanding of emptiness has matured, you are no longer worried about getting stuck in any of the relative view points. So you learn to take on a particular relative point and hold on to that until you overcome your weakness in that area. At this point your precept is to maintain integrity of the relative point you have taken, regardless of what it does to the previous 4 levels. Once you complete your training, you can use various relative points effectively when dealing with people and students in different mental contexts. In other words, #5 is just a training trick to get better with #4. In reality #4 is the top level, so that's where you want to be.

You see? So you don't have to think in terms of the 5 precepts all the time. As your insight and practice matures, your context will change - but if your understanding is right then your actions that come from your new mental context will still be correct fulfillment of the vows taken on the previous levels. Generally speaking, if you do something on your current level that looks obviously wrong on a previous level - it means you got something very confused.
Makes sense? Sorry, I know you want clarity, you want clear guidelines that can help with your day to day decision making in support of your practice. This may not be the answer you expected, but I hope it will make things clearer for you. Let me know if you have specific examples you want to analyze.

That's a great answer Andrei; I can appreciate the perspective which you chose to answer into. Personally, I feel as if though I went from the first level you describe into confusion. I am still keeping the precepts the same way, except now I feel like I am not going forward, backwards, or anywhere for that matter with practice. Controlling mental states is harder and less productive, and everything seems to be regressing in spite of the fact that I am practicing more than before.
I noticed your post about copyright - but I am not convinced.

ownership is arbitrary and can't be properly defined
I think it has a conventional and legal (law-of-the-land) meaning; for example:

When I'm an infant my parents give me food, clothing, etc. -- that isn't "taking what's not given".
When I'm a child and want more sweets than I'm permitted to buy, take money from my mother's purse without permission -- that is "taking what's not given".
When I'm adult, sign an employment contract, earn a salary -- that isn't "taking what's not given".
When I travel on a public footpath -- that isn't "taking what's not given" (because it's public, given to public use).

There are some edge cases, so people manage to argue over whether copyright is theft, whether intellectual property is a thing, and so on, but in general I think it's clear and not abstract.
You might have some personal or political belief such as "Property is theft!" -- I think the Vinaya (which are the detailed rules for monks) mention the King's law as a standard of conduct or definition of theft:

Should any bhikkhu, in what is reckoned a theft, take what is not given from an
  inhabited area or from the wilderness—just as when, in the taking of what is not given,
  kings arresting the criminal would flog, imprison, or banish him, saying,

“You are a
    robber, you are a fool, you are benighted, you are a thief”

—a bhikkhu in the same way
  taking what is not given also is defeated and no longer in affiliation.

See pages 51 through 52 of this document which details whether an object qualifies as "not given".
Lying is pretty objective, but also has its issues in getting proper communication across.
You might like to read or browse the The Patimokkha Rules (linked/referenced above) ... they're quite detailed, legalistic. The Chapter about "lying" starts on page 245, saying,

A deliberate lie is a statement or gesture made with the aim of
  misrepresenting the truth to someone else. The K/Commentary, summarizing
  the long “wheels” in the Vibhanga, states that a violation of this rule requires
  two factors:

Intention: the aim to misrepresent the truth; and
Effort: the effort to make another individual know whatever one wants to
  communicate based on that aim

So, "failure to communicate" doesn't count as lying ... unless your aim is to misrepresent the truth.
People in this discussion, at least, decided that the "precept" is about (specifically) lying, rather than (more generally) about right speech.
In right speech, abusive speech is subjective: some consider certain words abusive, so if you speak to them in such a manner it won't be right speech.
I suppose I try to use mild words always, use a neutral or formal "register", even though some people, friends, swear or tease each other for fun. I'm not saying that my doing so is "skillful", but I don't intend it to be offensive.
Others might not, and then there should be no violation of right speech in that situation even though everything you do is the same.
Well, here are some definitions of Right Speech. A lot of that is, hopefully, easy to understand.
Some of it is difficult, e.g., "the Tathagata ... has a sense of the proper time for saying them" -- I suppose that's a matter of wisdom and knowledge.
Occasionally it may be wrong not to speak (c.f. Ananda in AN 5.166).
Personally, I feel as if though I went from the first level you describe into confusion.
To avoid taking what's not given, if you want something, you can buy it, or be given it as a gift, or it's free (like air) ... otherwise not. Perhaps you can apply it to personal relationships too: people can't be given, aren't property, don't try to "take" them. Maybe consider what "right employment" means for a layperson, how to use wealth properly, and give to who needs a gift.
To avoid lying: I don't know, if you're tempted to lie then maybe think about why that temptation comes about, what gives rise to it? I've long thought that an ideal is that a person should see no need to lie.

Great response! I always find it difficult to accept that the precept of stealing assigns moral responsibility to a legislative process that is not morally responsible.


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How are good and bad Karmas determined in Buddhism?
One important thing that Hindus and Buddhists agree on is the law of Karma.  That is, there are certain actions which will lead a person to have a positive experience in future, either in this life or the next, and there are other actions which will lead a person to have a negative experience in future.  And Hindus and Buddhists also agree that ultimately the goal of life is not to just do good Karmas so you can have positive experiences in future, but rather to break out of he whole cycle of Karmas and their consequences.  Buddhists believe that this can be done through the Eightfold Path, and Hindus believe in other means like knowledge of the supreme being.
But my question is about what determines good Karmas and bad Karmas.  Hindus believe that the Vedas (and texts derived from them) tell us exactly what actions constitute good Karma and what actions constitute bad Karma.  But Buddhists reject the Vedas, so my question is, how do Buddhists determine what actions are good Karmas and what actions are bad Karmas?  Do Buddhist scriptures discuss how to determine this?
Note that I don't think the answer is "The Eightfold Path", because that's about what's required to break the cycle of Karma and consequence, whereas my question is about what's required to get positive experiences through the law of Karma.  Also, on a side note, do Buddhists simply classify Karmas into good or bad, or do they subdivide these categories further?  Because Hindus believe in a more fine-grained system where different kinds of good Karmas produce different kinds of positive experience.

Please see this answer on karma, rebirth and effects of karma on this life and future lives.
From the Nibbedhika Sutta:

"Intention, I tell you, is kamma. Intending, one does kamma by way of
  body, speech, & intellect.

In Buddhism, intention is the basis for karma. There are some guidelines on removing unskillful thoughts and qualities. The story of the blind elder monk Ven. Chakkhupala in Dhammapada 1 and the story of the hunter's wife in Dhammapada 124 further illustrates this.

Dhammapada 1: All mental phenomena have mind as their forerunner; they
  have mind as their chief; they are mind-made. If one speaks or acts
  with an evil mind, 'dukkha' (suffering) follows him just as the wheel follows
  the hoofprint of the ox that draws the cart.
Dhammapada 124: If there is no wound on the hand, one may handle
  poison; poison does not affect one who has no wound; there can be no
  evil for one who has no evil intention.

It appears that the simplest way to identify unskillful thoughts and actions, is whether they are imbued with the three poisons or not. And for skillful thoughts and actions, it's the opposite.
In the Vitakkasanthana Sutta, we find that unskillful thoughts imbued with desire/ greed, aversion/ hatred, or delusion have to be removed.
In the Vina Sutta:

"Monks, in whatever monk or nun there arises desire, passion,
  aversion, delusion, or mental resistance with regard to forms
  cognizable via the eye, he/she should hold the mind in check.
  [Thinking,] 'It's dangerous & dubious, that path, thorny & overgrown,
  a miserable path, a devious path, impenetrable. It's a path followed
  by people of no integrity, not a path followed by people of integrity.
  It's not worthy of you,' he/she should hold the mind in check with
  regard to forms cognizable via the eye.

And the same applies to the other senses.
You can find a similar discussion in the Aparihani Sutta where it talks about removing "evil, unskillful qualities such as greed or distress".
In the Sacitta Sutta, also teaching us to remove unskillful thoughts:

"If, on examination, a monk knows, 'I usually remain covetous, with
  thoughts of ill will, overcome by sloth & drowsiness, restless,
  uncertain, angry, with soiled thoughts, with my body aroused, lazy, or
  unconcentrated,' then he should put forth extra desire, effort,
  diligence, endeavor, relentlessness, mindfulness, & alertness for the
  abandoning of those very same evil, unskillful qualities.

Detailed classification can be found in the Abhidhamma in the volume called Dhammasangani ("Enumeration of Phenomena"). We can find a classification list in the work The Abhidhamma in Practice by N.K.G. Mendis:

Sa"nkhaaraa is a collective term for the other fifty cetasikas (mental factors). These
  fall into four groups:

Universal mental factors (sabba citta saadhaaranaa)
Particular mental factors (paki.n.nakaa)
Unwholesome mental factors (akusalaa)
Beautiful mental factors (sobhanaa)

You can read the details on this page for the full classification of the 50 cetasikas.
There are also other classifications there like the different types of cittas (momentary states of mind and consciousness) - vipaaka, kusala, akusala, kiriya. They have association with roots (hetu, mula - see below) and feelings (vedana) etc.

There are six roots. Three are kammically unwholesome (akusala); the
  other three may be either kammically wholesome (kusala) or
  indeterminate (abyaa-kata), depending on the type of consciousness
  they arise in. The unwholesome roots are greed (lobha), hatred (dosa),
  and delusion (moha). The three roots which are wholesome in some
  cittas and indeterminate in others are greedlessness (alobha),
  hatelessness (adosa), and undeludedness (amoha). Though these last
  three roots are expressed negatively they have positive
  manifestations. Greedlessness manifests as generosity and
  renunciation, hatelessness as loving-kindness, and undeludedness as
  wisdom or understanding.

The above are only the Theravada texts. There will undoubtedly be additional discussion on this, in the Mahayana texts.
You can find useful info also in Ven. Thanissaro's Kamma: A Study Guide.

OP: I think skillfull vs. unskillful has to do with what will lead you to liberation vs. what will serve to keep you in Samsara.  But my
  question is about what will serve to give you positive experience in
  Samsara vs. what will serve to give you negative experiences in
  Samsara.

Skillful thoughts and actions will give you a positive experience in Samsara and could also lead you to liberation. Unskillful thoughts and actions will give you a negative experience in Samsara.
But liberation requires much more than skillful thoughts and actions. It also requires one to abandon all the fetters.
For e.g. by practising one or more of the Brahmaviharas (loving kindness, compassion, empathetic joy and equanimity) which is skillful, one could obtain the pleasant experience of birth in the heavans. But this is not permanent.

I think skillfull vs. unskillful has to do with what will lead you to liberation vs. what will serve to keep you in Samsara.  But my question is about what will serve to give you positive experience in Samsara vs. what will serve to give you negative experiences in Samsara.

Updated answer.

That is, there are certain actions which will lead a person to have
  a positive experience in future, either in this life or the next,

The Pali suttas do not literally state this. The Pali suttas (eg. AN 6.63) state there are three results of kamma: (i) now; (ii) later; (iii) later again.
For example, the kamma of drinking alcohol has three results: (i) pleasure now; (ii) headache tomorrow; (iii) habit, craving or addiction later.
Next life kamma is an interpretation rather than a literal reading of the Pali suttas. In the Pali suttas, words such as 'birth' ('jati'), 'death' ('marana'), 'body'('kaya'; group) do not necessarily have a physical meaning.
The Buddhist commentaries & suttas (somewhere) state how the ordinary person views Dhamma is the opposite to how an enlightened person views the same Dhamma teachings. In the commentaries, this is known as the 'two truths'. The ordinary person reads everything as physical materialism where as the enlightened person reads everything as it really is. Thus, the Buddha does not speak lies when he uses language that can be interpreted in two-ways.
In is not correct to assert Buddhism teaches about past & futures lives because this is not literally said in the original scriptures (although is literally asserted in later scriptures & commentaries).

And Hindus and Buddhists also agree that ultimately the goal of life is not to just do good Karmas so you can have positive experiences in
  future, but rather to break out of he whole cycle of Karmas and their
  consequences. Buddhists believe that this can be done through the
  Eightfold Path, and Hindus believe in other means like knowledge of
  the supreme being.

The Buddhist idea seemed to exist systematically before the Hindu idea. At least the idea of moksha with Brahma appears to be not mentioned in the Pali suttas, which report discussions with Brahmans who followed the Vedas. While the early Upanishads are not mentioned in the Pali suttas, it appears the ideas in them about moksha seem to be either immature or not widespread at the time of the Buddha.

But my question is about what determines good Karmas and bad Karmas. Hindus believe that the Vedas (and texts derived from them) tell us
  exactly what actions constitute good Karma and what actions constitute
  bad Karma. But Buddhists reject the Vedas.

The Buddha did not reject anything in the Vedas he agreed was beneficial. The Pali suttas explicitly state the Buddha was a friend of the Brahmans and wished no harm to the Brahmans. When the Brahmans tried to argue (like Jews) they were a chosen or superior caste, born from Brahma's mouth, the Buddha replied if they do bad kamma how can they be superior?; to which the Brahmans agreed. So both Buddha & the Brahmans had respect for good kamma as a determinative factor for a superior 'birth' (status).

so my question is, how do Buddhists determine what actions are good Karmas and what actions are bad Karmas? Do Buddhist scriptures discuss
  how to determine this?

In Buddhism, the ten skilful kamma are non-killing, non-stealing, non-sexual-naughtiness, honest speech, pleasant speech, cordial-non-divisive speech, beneficial speech, non-greed, non-hatred & non-delusion. Apart from this, there are many other lists, such as in the Sigalovada Sutta.
In Buddhism, everything is determined on the basis of causing suffering/harm & leading to freedom from suffering/harm, which can be known via personal experience. Refer to the Kalama Sutta.

Note that I don't think the answer is "The Eightfold Path", because that's about what's required to break the cycle of Karma and
  consequence,

Correct.

Also, on a side note, do Buddhists simply classify Karmas into good or bad, or do they subdivide these categories further?

Basically two-categories, namely, wholesome/skilful & unwholesome/unskilful (although there is a sutta with four types: white, black, white-black, neither-white-black).
Naturally, there are more refined superior good kammas, such as excellent generosity, meditative heavenly jhana, loving-kindness (metta), serving arahants, etc.
For example, there are many different godly realms in Buddhism, which are the results of different kammas as well as human, animal, ghost & hell birth from different kammas.
Godly realms represent special attainments, such as worldly wealth, political power or higher spiritual qualities, such as psychic powers.
Human birth means being moral.
Animal birth is being immoral, ghost birth is being chronically craving & hell birth is suffering & torture.

Because Hindus believe in a more fine-grained system where different kinds of good Karmas produce different kinds of positive experience.

Buddhism is an experiential tradition. The degrees of kamma are known in the heart.

Karma is intentional thought. If the intention is associated with greed, hatred and ignorance, it's bad Karma. If the intention is associated non-greed, non-hatred, non-ignorance it's good Karma.

Good karma are intention which drive actions which mature into results which are deemed favorable and bad karma are intention which drive action which mature into results which are deemed unfavorable. Karma is the product of intentional action may it be mental, verbal or physical.

"how do Buddhists determine what actions are good Karmas and what
  actions are bad Karmas?"

Only Buddhas can determine what actions are good karma and what actions are bad karma.
Buddhas determine good and bad karma by looking at the past and present karma of beings. By knowing the karma of beings, they know what actions would propel those beings towards liberation, and these actions are then termed "wholesome".

"Do Buddhist scriptures discuss how to determine this?"

No. Explaining to a human being how to look at the past and present karma of beings would lead to madness. It is too complicated for us to comprehend this madness. Only Buddhas can comprehend it.

"what's required to get positive experiences through the law of
  Karma.?"

Read the suttas where the Buddha teaches what is required to get positive experiences.

"do Buddhists simply classify Karmas into good or bad, or do they
  subdivide these categories further?"

Buddhist classify karma into good, bad, neutral.

Please let me offer one other alternative: karma is not good or bad - it just is.
We have watched centuries unfold where we are told that this action is bad or that action is bad from pretty much a moral perspective. I would contend that morality has nothing to do with karma. Morality is a cultural concept whereas karma is a part of science and nature. The only "morality" rule in nature and science is the golden rule and this happens as empathy resulting from the byproduct of a communication tool developed in our frontal cortex. All other morality rules come from this or are merely attempts to control.
Now, that said, it is true that bad acts - those frowned upon by society - do create more "bad karma" the same way that acts we perform that the public likes create more "good karma". Crying creates sadness which creates depression while smiling creates happiness which leads to good feelings. But an act we could consider bad at one time would be good at another.
Karma is little more than the cosmic momentum created when we say or think or perceive or do something. It alters matter and perceptions and body reactions and the like and this results in a mountain of consequential effects. It's delineation as good or bad depends on the context and "experiencer".

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Can a non-Buddhist get Nirvana?
No religion teaches what Buddhism teaches at its core. A true Hindu or Christian or Muslim believes in God and soul.
Can a Hindu or a Christian or a Muslim, who is not aware of Buddhist philosophy, get Nirvana?
If yes, how? Otherwise, why doesn't everyone become a Buddhist to attain supreme bliss?

Can a non-Buddhist get Nirvana?

Buddhism, Hinduism, Islam etc. are just words, conventional language. What is important is the teaching and practice of the teaching.
In the famous Maha-parinibbana Sutta, there is a passage where the Buddha explains to the wandering ascetic Subhadda, that "in any doctrine & discipline", that does not contain the Noble Eightfold Path, enlightened beings cannot be found.
It shows that only teachings that contain the Noble Eightfold Path can lead to freedom from suffering, to Nibbana.
The quoted passage can be found below.

Then Subhadda went to the Blessed One and exchanged courteous greetings with him. After an exchange of friendly greetings & courtesies, he sat to one side. As he was sitting there, he said to the Blessed One, "Venerable sir, these brahmans & contemplatives, each with his group, each with his community, each the teacher of his group, an honored leader, well-regarded by people at large — i.e., Purana Kassapa, Makkhali Gosala, Ajita Kesakambalin, Pakudha Kaccayana, Sañjaya Belatthaputta, & the Nigantha Nataputta: Do they all have direct knowledge as they themselves claim, or do they all not have direct knowledge, or do some of them have direct knowledge and some of them not?"
"Enough, Subhadda. Put this question aside. I will teach you the Dhamma. Listen, and pay close attention. I will speak."
"Yes, lord," Subhadda answered, and the Blessed One said, "In any doctrine & discipline where the noble eightfold path is not found, no contemplative of the first... second... third... fourth order [stream-winner, once-returner, non-returner, or arahant] is found. But in any doctrine & discipline where the noble eightfold path is found, contemplatives of the first... second... third... fourth order are found. The noble eightfold path is found in this doctrine & discipline, and right here there are contemplatives of the first... second... third... fourth order. Other teachings are empty of knowledgeable contemplatives. And if the monks dwell rightly, this world will not be empty of arahants."

Many religions teach the eightfold path - just not by that name!

Attaining Nirvana is not about labeling one self as Buddhist. To attain Nirvana you should follow the path to Nirvana. Any body following this path will reach the destination regardless of what they call themselfs. So you can call yourself a Buddhist, Hindu, Christian, Muslim, Jain, Jew, etc. to start with but what matters to realise Nirvana is the threefold practice.
As the realities unfold through direct insight your faith in Buddhism concepts also will get stronger at level of experiential verification, i.e., you have see in reality that the theory is inline with reality. Likewise at some point you will see there is nothing worth identifying as self or nothing that you completely can control. This is the Buddhist concept of non/not self.

But in the threefold practice, there is a mention of right view under category wisdom. Is faith in Atman or soul a right view ?

No it is not the right view but right view is or any other path factor is a gradual process. It does not happen all at once. Little by little you should straighten your view. Also replacing one view with another view without experiential understanding also has little value through even at a conceptual level right view is better.

why doesn't everyone become a Buddhist to attain supreme bliss?
I think that a "true" Christian may have beliefs which (may) help them to find some peace or solace, and which have some similarities at least in their effect (if not in their form) to Buddhist beliefs. I guess for example, faith that "It's God's will" or "This is part of God's plan", and the "Lord's Prayer" that, "Let thy will (not my will) be done", might help to alleviate a personal craving for something to be other than it is (and therefore, alleviate that type of dukkha). Similarly the virtue of Charity (which is Christianity's "greatest" virtue, and the second of the two "great commandments") remind me of some things which the Dalai Lama has written, about caring for other people to avoid being trapped in your own "self".
I know less about Hinduism; but a while ago I asked about this story which I half remembered, Self like a diamond, because I assumed its moral was Buddhist: I recently discovered that story is from a Shivaite tradition ... which I haven't been taught, but of which I get the impression that the principal doctrine, attitude, or action seems to be something like, "Everything is God, let me lose my self in order to find or be with God" ... so again there's some kind of non-self doctrine happening there.
I'm not trying to say that these other traditions are as good as Buddhism, nor the same as Buddhism ... but perhaps they address or attempt to address some of the same human frailties ... and people's needs are at least partly addressed by the religion they have.
Another answer to your question is that there are historical reasons. The Buddhadharma has existed in the West for only about the last 100 years or so ... if you learned any religion from your parents, it probably wasn't Buddhism.
Sometimes people who have any existing religion might be averse to learning or practicing a new one: Islam may penalize apostates; Judaism (and Christianity) have the first commandment; see also Meditating and including buddhist philosophy in your life without abandoning previous religious beliefs?
Then again, maybe your premise ("why doesn't everyone become a Buddhist") is wrong ... maybe everyone does become Buddhist! I discovered that "zen" has become a well-known, everyday or "current" adjective in France ... a synonym for cool or calm, detached, unstressed. So everyone has some idea of what it means, what its values are. People who are interested can find more ... there are many centres (e.g. in Paris), there's Plum Village, there are books in a large local book store, etc.
Also, as I said in How to explain what Buddhism is?, I've found that not everyone seems to feel the need for what Buddhism has to offer ... and/or that Buddhism isn't sufficiently well taught, well explained to  people ... so that's another reason that not everyone is interested. I won't say "there aren't enough good Buddhist role models for people emulate" because maybe that's not true, however maybe those good role models (who other people might meet every day in society) aren't people who preach, or teach that Buddhism is essential -- How are Buddhists supposed to spread Buddhism?
Finally the answer I accepted to that question suggests that there are different forms of Buddhism ("each branch has a slightly different take on what the problem is that Buddhism is meant to solve"). If you think there's "one true form" of Buddhism which results in "getting Nirvana", you might note that not even all "Buddhists" will become that type of Buddhist.

Nirvana is often thought of as a Buddist exclusive thought but Dictionary.com difines Nirvana as a Hindu concept also and adds "a place or state characterized by freedom from or oblivion to pain, worry" which could well be applied to the Christian concept of heaven.

Buddhist Nirvana is based upon the concept of Anatta which is a departure from the Hindu belief of atman.

No religion teaches what Buddhism teaches at its core.

If the teachings of the religion are complete, they would be the same as the teaching of another complete religion. By "complete" I mean universally acceptable. If the teachings of a religion cause conflict in an individual, the teachings are clearly not complete.
So, assuming what's being taught in Buddhism lets the individual live a conflict free life (or enlightenment), then any religion's teaching that let the individuals live a conflict free life is ok to be followed.

A true Hindu or Christian or Muslim believes in God and soul.

First thing - what you believe in, doesn't matter. What really is true - does matter. You may believe that Earth is flat but it doesn't matter. What matters is that Earth is spheroidal and just because you don't believe in it, doesn't change it.
Believing or not believing in God and Soul is immaterial. What is of importance is to know whether God and Soul really do exist. And if they do, then what are they?
Water is called with different names in different cultures. But all those names actually point to the same liquid with unique attributes. If God and Soul are real, then every complete religion would acknowledge them. And if the religion does not acknowledge them, and given that they are real, the religion cannot lead you to a conflict free life because the teachings of the religion are in conflict - the religion is saying that God and Soul do not exist when they actually do.

Can a Hindu or a Christian or a Muslim, who is not aware of Buddhist philosophy, get Nirvana? If yes, how?

Nirvana is a state. It is not tied to any religion. It is a real state (of an individual) and therefore in complete religions it should have an acknowledgement.
This state, which is called Nirvana in Buddhism, may be called with other names in other religions but the Nirvana of Buddhism would be same as Nirvana of Hinduism, Christianity or Islam, even if it is called with different names in those religions.
The relation that a Hindu mother feels with her child is the same as a Christian mother feels with hers is the same as a Muslim mother feels with hers. The relation is called by different names but the feeling is exactly the same.

Otherwise, why doesn't everyone become a Buddhist to attain supreme bliss?

Because it doesn't matter what path you take. What matters is that you attain enlightenment.

It is indeed possible to become enlightened (i.e. attain Nibbana) without becoming a Buddhist and without encountering the teachings of a Sammasambuddha. Such beings are called Pacceka Buddha or Pratyeka Buddha (see here and here), which literally means "private Buddha" or "lone Buddha". You can find some details in this question.
It is also true that Buddhism is very far away from (almost) every other religion, because of Anatta (no eternal self), and also the middle way between eternalism and annihilationism (see this answer).
In MN2, the Buddha stated clearly that having the wrong view of an eternal, independent and standalone self is not conducive to attaining Nibbana (permanent happiness and freedom from suffering). If one believes in an Eternal God, then this implies a belief in an eternal self who is the Eternal God, and therefore is also a wrong view, from the Buddhist perspective.
Not everyone becomes a Buddhist, partly because the full depth of the teachings may not be easy for all to understand as the Buddha stated in MN26:

'This Dhamma that I have attained is deep, hard to see, hard to
  realize, peaceful, refined, beyond the scope of conjecture, subtle,
  to-be-experienced by the wise. But this generation delights in
  attachment, is excited by attachment, enjoys attachment. For a
  generation delighting in attachment, excited by attachment, enjoying
  attachment, this/that conditionality & dependent co-arising are hard
  to see. This state, too, is hard to see: the resolution of all
  fabrications, the relinquishment of all acquisitions, the ending of
  craving; dispassion; cessation; Unbinding.

To be honest, even for Buddhists, Anatta and dependent origination may be hard to fully understand and realize through their own experience and discernment. For this is needed (along with other things), to attain stream entry.
However, according to Buddhism, every person, regardless Buddhist or non-Buddhist, have the right to impermanent forms of happiness, including the right to be reborn in the heavans.
Christians who practise John 13:34-35 and Hindus who practise BG12.13-14, would be fulfilling the Buddhist practice of the Brahmaviharas (at least one or two of them), which should lead them to heavan (but that would not be permanent).
I once asked a similar question here, where you can find some quotes showing that the description of Nibbana sounds similar to the description of Tao and Brahman/Atma. So, you can also draw some relief from there that there is some degree of overlap, but nevertheless, Anatta is a core part of the teachings and cannot be compromised.

It depends more on what each teacher teaches & less on what the  religion of the teacher is.
It depends more on the students ability to teach themselves the important details that even the best teachers cannot teach.
According to the Tipitaka, if a non-Buddhist teacher teaches something similar to the Eightfold Path then the better the chance that the teacher's students will become arahants.

Absolutely – nirvana is religion-agnostic. It doesn't matter what religion you consider yourself to belong to as these are essentially just labels anyway; what's important is what you practice.

"Can a Hindu or a Christian or a Muslim, who is not aware of Buddhist
  philosophy, get Nirvana?"

Yes.

"If yes, how?"

With insight gained from meditation.

"Otherwise, why doesn't everyone become a Buddhist to attain supreme
  bliss?"

You don't need to become/be a Buddhist to attain supreme bliss.

I have practiced Theravadin mindfulness meditation for more than 50 years. My meditation teacher, a Theravadin Buddhist monk, The Venerable Ananda Bodhi, formally told me that attained Enlightenment in 1979. I can say that Enlightenment is a psychological state of mind and that the belief is God would not prevent such Enlightenment. If you want to know more details, you can read one of my books available on line. My name is Ronald Cowen. I also have a Buddhist name, Sila Ananda, given to me during my novice ordination thirty years ago.

Can a Hindu or a Christian or a Muslim, who is not aware of Buddhist philosophy, get Nirvana?

No. If they accidentally got to Nirvana, they would be a Buddha themselves. In summary, the teachings of the above three religions cannot reach Nirvana.

Otherwise, why doesn't everyone become a Buddhist to attain supreme bliss

Because not everyone wants to abandon self, completely, 100%. Most Buddhists cannot even reach Nirvana so how do you expect the non-Buddhists to do so? The Buddha did not teach his dhamma was for all people.

And, Master Gotama, when having directly known it, you teach the Dhamma to your disciples for the purification of beings, for the
  overcoming of sorrow & lamentation, for the disappearance of pain &
  distress, for the attainment of the right method & for the realization
  of Nibbana, will all the world be led [to release], or a half of it,
  or a third?"
When this was said, the Blessed One was silent.
AN 10.95

Then, having understood Brahma's invitation, out of compassion for beings, I surveyed the world with the eye of an Awakened One. As I did
  so, I saw beings with little dust in their eyes and those with much,
  those with keen faculties and those with dull, those with good
  attributes and those with bad, those easy to teach and those hard,
  some of them seeing disgrace & danger in the other world. MN 26

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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Emptiness in Theravada and Mahayana
What is the difference between the concept of emptiness (Śūnyatā in Sanskrit, or suññatā in Pali) in the Theravada tradition and the concept of emptiness in the Mahayana tradition?
From my basic understanding, Theravada emptiness is only regarding the self, while Mahayana emptiness is regarding all things. Is this true?
Or does Theravada also teach the emptiness of all things (e.g. in the sutta about foam and bubbles)?
Are these (Theravada emptiness and Mahayana emptiness) really completely different, or at some level, do they allude to the same thing?
For Theravada, could it be, that the emptiness of self is important for the path to ending suffering, but the emptiness of all things is not important for the path to ending suffering (as per the Parable of the Poisoned Arrow and the Parable of the Leaves in the Forest)?
I found the following quote from this answer interesting:

It is said that beginner practitioners ("hinayana") only understand
  corelessness of beings (anatta), but still assume various stuff to be
  objectively/ontologically existing. This results in them erroneously
  reifying such concepts as the five skandhas, 12 nidanas, 4 noble
  truths, nirvana, and enlightenment. Advanced practitioners
  ("mahayana") clearly understand that all knowable phenomena without
  exception are contextually defined composites.

from the mahayana persecptve i believe that you generally are right. not sure from the theravada perspective. also, i believe that zhiyi taught that for "tripitaka buddhism" all dharmas are empty, but only when the arhat / solitary buddha / transformation body realises that

A nice summary of Pali Canon's view on emptiness can be found in book: "The Concept of Emptiness in Pali Literature" available here.

Another nice summary of the Pali Canon's view on emptiness can be found in Ven. Thanissaro's commentary or translator's introduction of MN122.

Edited question to add this: For Theravada, could it be, that the emptiness of self is important for the path to ending suffering, but the emptiness of all things is not important for the path to ending suffering (as per the Parable of the Poisoned Arrow and the Parable of the Leaves in the Forest)?

The following answer is informed by Insight into Emptiness by Khensur Jampa Tegchok who was a former abbot of Sera Je Monastery.
Presentation of Tenets
According to what is currently taught in contemporary Tibetan Buddhist monasteries, the view of selflessness differs between proponents of the Fundamental Vehicle school (which includes Theravada) and the Universal Vehicle school (or Mahayana). The common delineation is given as four different (ancient) tenet systems regarding selflessness:

Vaibhashika
Sautrantika
Chittamatra
Madhyamaka

The first two tenet systems belong to members of the Fundamental Vehicle school while the latter two are ascribed to the Universal Vehicle.
Here is a brief breakdown of the view of selflessness as it differs among these tenet systems:
Selflessness of persons (from course to subtle)

Emptiness of a permanent, unitary, and independent person
Emptiness of a self-sufficient, substantially existent person
Emptiness of an inherently existent person

Selflessness of phenomena

Emptiness of existing by its own characteristics as the basis or
referent of its name
Emptiness of the form and so forth and a valid cognizer of it being
different substances (different substantial entities)
Emptiness of true existence (existing without being posited by the
force of appearing to a nondefective consciousness)
Emptiness of inherent existence (existing from its own side,
existing by its own characteristics, and so on)

Definitions:

Permanent means something that does not change from one moment to the next
Impermanent means that something changes under the influences of causes and conditions
Unitary is something that is one seamless whole that has no parts
Independent has different definitions given different contexts:

Independent is something not being affected by or not relying upon causes and conditions
In the context of a person it means being independent of the aggregates as well
In Prasangika it means existing without depending on being merely imputed by name and concept

Self-sufficient means being able to exist independently in a
self-supporting manner, without depending on anything else, such as
the aggregates
Substantially existent person means being able to know such a person
exists without the appearance of the aggregates

In general, it is said that the Fundamental Vehicle systems do not subscribe to the selflessness of phenomena. Furthermore, the Vaibhashikas only subscribe to the lack of a permanent, unitary and independent person. That is they do believe that a self-sufficient, substantially existent person exists. The Sautrantikas on the other hand do not believe in a self-sufficient, substantially existent person nor do any of the other tenet systems.
All of that is to say, it is my understanding that the modern day Theravada is most closely aligned with the Sautrantika tenet system.

Emptiness in Pali refers to 'empty of self & anything pertaining to/belonging to self' (SN 35.85).
Mahayana argues things are empty of independent existence because they are dependent on causes & conditions. Mahayana says dependent origination is emptiness but this does not match the Pali because, in Pali, dependent origination explains the arising of suffering.
The Mahayana is different to the Pali because, in Pali, Nirvana is not dependent on causes & conditions but Nirvana is empty. In Pali, everything is empty (of self) when seeing clearly. It is not required to discern causes & conditions. This is why SN 35.85 states the sense spheres are empty, without going into any other explanation.
The sutta about foam (Phena Sutta) is not about emptiness (sunnata). It is best to read a proper translation of it, such as Bhikkhu Bodhi's at Sutta Central.
Mayahana ideas about emptiness are only intellectual and not meditative because, in Pali or meditation, phenomena arise according to their function. While consciousness, for example, is impermanent & arises & ceases based on causes & conditions, whenever consciousness functions, it performs the function of consciousness, namely, seeing, hearing, tasting, touching, smelling & cognising. Consciousness, when it functions, is always consciousness. Consciousness is never empty of being consciousness. Thus the Pali teaches: "Why do you call it consciousness? Because it cognises, thus it is called consciousness" (MN 43; SN 22.79).
To believe consciousness really does not exist because it is dependent on neurons, atoms, electricity, sense organs, the body, etc, is merely intellectual and unrelated to meditation. In real meditation, consciousness is discerned as being consciousness but empty of self and also impermanent & dependent on sense bases. However, when consciousness arises, it functions as consciousness rather than is not consciousness or functions as something else. Consciousness is consciousness but is void of self because consciousness is sense awareness where as 'self' is a thought (sankhara aggregate).
Mahayana ideas are the product of thinking rather than direct seeing. This Mahayana ideas should not even be labelled as "beginners" because they do not even arise from meditation but arise from reading books.

To all Mahayana practitioners here: please refrain from debating in the comments. If you disagree with something said, or wish to make a point - please consider posting your own answer. Thank you.

An emptiness in theravāda tipitaka:

Anattā = no monopoly power in everything. Just being/having by own special character that must depending on many various external causes. This is right view.
Attā vanishing = there is some monopoly power person vanishing.  This is wrong view.
General adjective/adverb/predicate = just a predicate of some words in the sentence that maybe in the context about view or maybe not.


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Should I decrease the amount of time I practice concentration meditation?
I have been following buddhist practices for little over three years now, and samadhi - or concentration, as you prefer - meditation was obviously part of my practice. As I was often taught from some of the books from which I learned meditation, I used samadhi meditation as a way of stabilizing my mind and of being able to do insight practices, beyond just getting more relaxed.
One of my primary concerns after having exited the "bubble" of samadhi meditation after a long time is that I feel that some of the daily-life difficulties that I was somehow able to attenuate with concentration meditation are now reappearing, although with much less strength. More precisely, since when I needed to decrease the time for samadhi meditation I have been experiencing more mood swings, a little more anger, sometimes even a bit of depression, but at the same time I also felt more connected with the environment around me. Just a few months ago, when my samadhi meditation routine was more strong, I kind of avoided part of the suffering surrounding myself by making use of my concentration abilities.
This left me wondering whether I should try to tackle some of my personal problems through insight or other practices in a more definitive way, rather than trying to avoid them by shifting my concentration to more tranquil places. I am not at all against consistently practicing concentration meditation, but sometimes it takes more time than I have; also, I think to have heard time ago the Buddha criticizing a routine composed of just samadhi meditation. Actually that seems a reasonable recollection, since the elaboration of the four noble truths and of the noble eightfold path from the Buddha seem to be oriented toward solving the problems of existence in a more definitive way, while, as I was taught, the jhanic states are only temporary and shouldn't be considered otherwise.

Although Buddhism Stack Exchange discourages it, you are free to bring relevant content and observations as far as I'm concerned. My two primary questions here, though, are contained in the title and at the beginning of the third paragraph: This left me wondering whether I should try to tackle some of my personal problems through insight or other practices in a more definitive way, rather than trying to avoid them by shifting my concentration to more tranquil places. (Take this as an indirect question.) So well, try to respect these constraints.

Concentration meditation is only a tool to temporary suppress your problems and hindrances.  It is not a self-contained technique for eradicating them.  This was one of the Buddha's great discoveries - an obstacle that he saw past when he was under the teaching of Uddaka Ramaputta and Alara Kalama.  Concentration is only valuable insofar as it aids in insight practice.  As the Buddha says, “When my concentrated mind [in the fourth jhana] was thus purified, bright, unblemished, rid of imperfection, malleable, wieldy, steady, and attained to imperturbability, I directed it to..." (MN 36.38).  The malleable and clear mind that you enjoy following samadhi is not an end in itself but needs to be directed back to the world of form.  That includes all of your mental hangups, psychological issues, etc.  The techniques for doing this are vast and include everything from mindfulness practices to Zen koans.
Ultimately, concentration meditation and insight practice go hand in hand.  They add value and support to each other making either practice greater than it would be on its own.  You don't need to abandon samadhi practice.  Just make sure you are using it effectively.

I am not an expert in meditation, and you may be more experienced than me. But I will quote from other sources.
The Yuganaddha Sutta states that insight and tranquility can be developed in any order. So, you should not feel guilty about whichever method that you may choose to practise.

"There is the case where a monk has developed insight preceded by
  tranquillity. As he develops insight preceded by tranquillity, the
  path is born. .....
"Then there is the case where a monk has developed tranquillity
  preceded by insight. As he develops tranquillity preceded by insight,
  the path is born. .....
"Then there is the case where a monk has developed tranquillity in
  tandem with insight. As he develops tranquillity in tandem with
  insight, the path is born. He follows that path, develops it, pursues
  it. As he follows the path, developing it & pursuing it — his fetters
  are abandoned, his obsessions destroyed.

From your description, your problem is mainly increased mood swings, anger and depression when you're not meditating. For this, insight meditation could be helpful.
Ven. Yuttadhammo writes in this chapter entitled "Daily Life" of his booklet How To Meditate (which in my opinion is primarily based on insight meditation):

Further, one can apply the same technique to any small movement of the
  body – for instance when bending or stretching the limbs, one can note
  “bending” or “stretching”. When moving the limbs, “moving”. When
  turning, “turning”, and so on. Every activity can become a meditation
  practice in this way; when brushing one’s teeth, “brushing”; when
  chewing or swallowing food, “chewing, chewing”, “swallowing,
  swallowing” and so on.
When cooking, cleaning, exercising, showering, changing clothes, even
  on the toilet, one can be mindful of the movements of the body
  involved, creating clear awareness of reality at all times. This is
  the first method by which one can and should incorporate the
  meditation practice directly into ordinary life.
The second method is the acknowledgement of the senses – seeing,
  hearing, smelling, tasting and feeling. Ordinary sensory experience
  tends to give rise to either liking or disliking; it therefore becomes
  a cause for addiction or aversion and ultimately suffering when it is
  not in line with one’s partialities. In order to keep the mind clear
  and impartial, one should always try to create clear awareness at the
  moment of sensory experience, rather than allowing the mind to judge
  the experience according to its habitual tendencies. When seeing,
  therefore, one should know it simply as seeing, reminding oneself
  “seeing, seeing”. ....
Practicing in this way, one will be able to receive the full spectrum
  of experience without compartmentalizing reality into categories of
  “good”, “bad”, “me”, “mine”, “us”, “them”, and so on. As a result,
  true peace, happiness and freedom from suffering is possible at all
  times, in all situations. Once one understands the true nature of
  reality, the mind will cease to react to the objects of the sense as
  other than what they truly are and be free from all addiction and
  aversion, just as a flying bird is free from any need for a perch on
  which to cling.
This then is a basic guide to practice meditation in daily life,
  incorporating the meditation practice directly into one’s life even
  when not formally meditating. Beyond these two methods, one can also
  apply any of the objects discussed in the first chapter – pain,
  thoughts, or the emotions.

In this TED Talk video, Prof. Zindel Segal shows how mindfulness and insight meditation techniques were adapted to Mindfulness Based Cognitive Therapy (MBCT) to prevent recurrence of depression and chronic unhappiness. He shows some research evidence including MRI scans of patients who have become more disengaged from the triggers that make them depressed.

Mindfulness-Based Cognitive Therapy (MBCT) is designed to help people
  who suffer repeated bouts of depression and chronic unhappiness. It
  combines the ideas of cognitive therapy with meditative practices and
  attitudes based on the cultivation of mindfulness. The heart of this
  work lies in becoming acquainted with the modes of mind that often
  characterize mood disorders while simultaneously learning to develop a
  new relationship to them. MBCT was developed by Zindel Segal, Mark
  Williams and John Teasdale, based on Jon Kabat-Zinn’s
  Mindfulness-Based Stress Reduction program.

Please also see this answer and this question.

You have the right idea. As the Visuddhimagga states, full samadhi does not provide insight but upacara samadhi (another name for insight meditation or vipassana meditation) does provide insight into personal emotional problems and into how the mind actually works. Modern emotional problems are related to an abusive or dysfunctional family background and manifest as problems with self-love and finding love in adult life. The Buddha did not deal with or talk about this kind of suffering or how it is best treated. Although I practiced traditional mindfulness meditation for over 50 years, I recommend that you try a mindfulness center that offers both MBSR and psychotherapy. You can read my books to get a more Buddhist perspective. But I must warn you, Buddhist psychology is very difficult to understand. My name is Ronald Cowen.

Your view is wrong, because it attacking your concentration meditation.
Your daily life is difficult, because your sīla is not good enough. This is the important cause of your life impact, not concentration meditation.
What is sīla?

Observing precepts.
Manners behavior.

If you have manners behavior, you will prepare your daily lifetime much enough for each concentration meditation. For the example (from pali canon), you can make a table of daily life such as "I will do whole day meditation 1 day per week and everyday when laying on bed", etc. This is the reason that why we have uposatha day.

Lord Buddha have taught We shouldn't  give up our all console for the religious purpose.

I wrote just a few time, not all console >>  "I will do whole day meditation 1 day per week and everyday when laying on bed", etc.


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How can I explain soullessness to other one?
One of my friend don't accept Buddhism theory of soullessness.She is also buddhist.So my question is how can I explain the soullessness to her?

Both soul exists and soul does not exist are extreme view:

Ananda, if I — being asked by Vacchagotta the wanderer if there is a self — were to answer that there is a self, that would be conforming with those brahmans & contemplatives who are exponents of eternalism [the view that there is an eternal, unchanging soul]. If I — being asked by Vacchagotta the wanderer if there is no self — were to answer that there is no self, that would be conforming with those brahmans & contemplatives who are exponents of annihilationism [the view that death is the annihilation of consciousness]. If I — being asked by Vacchagotta the wanderer if there is a self — were to answer that there is a self, would that be in keeping with the arising of knowledge that all phenomena are not-self?

Ananda Sutta
Simply there is nothing worthy of identifying as self, because you are not in control, whatever you identify as self are not entirely pleasant.

Ask her to point out anything that qualifies as a soul. Then she will tell you something that comes under the 5 aggregates. Then you can teach her the Anatta-lakkhana Sutta

I have practiced mindfulness meditation and studied the Theravadin Abhidharma for more than 50 years. I can tell you with absolute certainty that Buddhist psychology cannot be understood without relevant experiences in advanced states of mindfulness meditation. Buddhist literature is not able to deal with the sophisticated definitions and arguments offered modern philosophy and psychology. There is indeed a mental organism that reincarnates from lifetime to lifetime. The Buddhist description of this organism is incomplete. I suggest that you and many Buddhist monks do not know and do need to know what this organism looks like or how it actually behaves. Such knowledge is irrelevant to achieving Enlightenment. If you really want to more about what I have discovered in meditation, you can read my books. Both you and your friend have no way of knowing what the concept of no-self or soul really means. My name is Ronald Cowen.

Is there problem with her's devotion?

"there is indeed a mental organism that reincarnates from lifetime to lifetime"?

This mental organism consists of a vast system of chakras and nadis. It has been described in many spiritual texts. Catching glimpses of it is a common experience in meditation. Historically, Sariputra studied this system on an atomic level using the siddhi called anima. He wrote the earliest versions of the Theravadin Abhidharma that describes the citta-vithi (thought-processes) of mental atoms.

Both claims "the soul exists" and "the soul does not exist" are correct, as long as they are not coming from ignorance.
According to the Buddha ignorance is having the view "self exists".
Thus it follows ...

If you claim "the soul does not exist", your claim is correct as
long as it is not coming from the view "self exists".
If your friend claims "the soul exists", her claim is correct as
long as it is not coming from the view "self exists".

Now listen carefully as I will speak ...

When a being holds the view "the soul exists", that being, at the time of holding onto this view, must also hold the view "self exists".
Why is that so?
In order for the soul to exist, there must be a cognition of existence of the soul.
With cognition of existence of the soul, even if the soul truly does not exist, the soul exists.
Thus, for existence of the soul to be cognized, a cognition of existence of a soul is needed, and what else is a cognition of existence of a soul then a kind of self itself?
Thus, in order for the soul to exist, there must be a kind of self with a cognition of existence of a soul.
That is why a being who holds the view "the soul exists", also holds the view "self exists".

When a being holds the view "the soul does not exist", that being, at the time of holding onto this view, must also hold the view "self exist".
Why is that so?
In order for the soul to not exist, a cognition of existence must not exist.
Without cognition of existence, even if something/anything truly exists, nothing exists.
Thus, for existence not to be cognized, a cognition of existence must not exist, and what else is a non existent cognition of existence then non existence of self itself?
Thus, in order for the soul not to exist, there must be non existence of a self.
That is why a being who holds the view "the soul does not exists", also holds the view "self does not exist".
When a being holds the view "self does not exist", that being, at the time of holding onto this view, must also hold the view "self exists".
Why is that so?
In order for the self to not exist, there must be a cognition of non existence of the self.
Thus, for non existence of the self to be cognized, a cognition of non existence of the self is needed, and what else is a cognition of non existence of a self then a kind of self itself?
Thus, in order for the self not to exist, there must be a kind of self with a cognition of non existence of the self.
That is why a being who holds the view "self does not exist", also holds the view "self exists".
That is why a being who holds the view "the soul does not exist", also holds the view "self exists".

...
This being said, having a view "the soul exists" or having a view "the soul does not exist", can both come from the ignorant view "self exists" described above, which is, according to Buddha, ignorance. Which is, according to Buddha, the cause of rebirths and all the mass of suffering.
That being said, all views, including the views "the soul exists" and "the soul does not exist", must be abandoned as they do not lead to the cessation of suffering. In the same way as you would let a bird you caught with your hand, thirsty for freedom, out of your hand, all views must be abandoned.
http://www.accesstoinsight.org/tipitaka/sn/sn44/sn44.006.than.html
Speculating about these views does not lead to their abandonment.
Meditating and reaching complete cessation, coupled with insight, leads to their abandonment.
Only then, once these views have been abandoned and ignorance removed in its entirety, one can, out of compassion for other beings, expound the truth and use such terms as "the soul exists" and/or "the soul does not exist" as a vehicle that can be used by beings to achieve liberation.

"order for the soul to not exist, a cognition of existence must not exist. Without cognition of existence, even if something/anything truly exists, nothing exists."What do you mean it?

Let me put it this way: "In order for the soul to not exist, a cognition must not exist. Without cognition, even if the soul truly exists, the soul does not exist." Explanation: Without cognition, nothing exists, not even the soul.


text:
The fourth path to attaining arahantship
From the Yuganaddha Sutta, there are four paths described:

Development of insight preceded by development of tranquility
Development of tranquility preceded by development of insight
Tranquility developed in tandem with insight
Mind's restlessness concerning the Dhamma well under control

From my understanding, the first three are about vipassana (insight) and samatha (tranquility).
Questions:

How does the fourth path work? Please elaborate on the fourth path.
How does one practise that? Please provide details.
Why is vipassana and samatha not required on the fourth path?

Ven. Ananda said: "Friends, whoever — monk or nun — declares the
attainment of arahantship in my presence, they all do it by means of
one or another of four paths. Which four?
"There is the case where a monk has developed insight preceded by
tranquillity. As he develops insight preceded by tranquillity, the
path is born.  .....
"Then there is the case where a monk has developed tranquillity
preceded by insight. As he develops tranquillity preceded by insight,
the path is born. .....
"Then there is the case where a monk has developed tranquillity in
tandem with insight. As he develops tranquillity in tandem with
insight, the path is born. .....
"Then there is the case where a monk's mind has its restlessness
concerning the Dhamma [Comm: the corruptions of insight] well under
control. There comes a time when his mind grows steady inwardly,
settles down, and becomes unified & concentrated. In him the path is
born.
He follows that path, develops it, pursues it. As he follows the
path, developing it & pursuing it — his fetters are abandoned, his
obsessions destroyed.
Yuganaddha Sutta

There are some interesting commentaries on this sutta here by Piya Tan, here by Ven. Anālayo and here by Ven. Kaṭukurunde Ñāṇananda.

I am not inclined to support the views of Analayo & Nanananda. The comments of Bhikkhu Bodhi in Piya Tan seem reasonable, which would also imply a non-returner, who has already developed samatha & vipassana.

I'm inclined towards Piya Tan's (or is he quoting Bhikkhu Bodhi?) comment on the fourth path: "The story of how Bāhiya Dārucīriya awakens by just listening to the Buddha as related in the (Arahata) Bāhiya Sutta (U 1.10) should be carefully examined: note especially how the Buddha skillfully calmed Bāhiya’s mind."

on 2nd thought, i think Nanananda's view is reasonable however it renders the sutta idiosyncratic, i.e., merely reflective of Ananda's alleged arahantship, which itself is a difficult to believe story. the idea that Ananda attained arahantship when his head lay on a pillow is far-fetched to me.

The 4th is a Ch'an (Zen) path. Buddha taught many paths, but for those converted to the Pali Canon regarded that's the totality of Buddhavacana this 4th path is not designed for them, due to their "citta capacity"; a rice bowl holds 100ml of water, but the ocean with all the water in the world could never spill. Hence none elaboration nor any Abidhamma text to explain, except maybe Vismgg. - Buddhaghosa imported Mahayana teachings to help these incomplete teachings; like the Pali scholars today stealing Mahayana doctrines - but mostly for fame. ~ I'm joking! :D, yet it is not a joke :|

How does the fourth path work? Please elaborate on the fourth path.
By attaining “anariya jhanas”, one can attain only ceto vimutti. Thus to achieve all of the four paths, one has to practice “ariya jhanas”. Only this second Ariya Jhana will lead to  magga phala with panna vimutti.
The fourth path does not involve samatha meditation. It is completely a  vipassana meditation. In Pali this fourth method is called **Dhamma Uddhacca Vigghahita Maanasan”. Unlike the other three methods, it takes only a very short time to come to realization through this method, but only a highly developed person can do this. This method is not for you and I. The only Ariya Meditation that may help the ordinary folk is the Savitakka/Savicara mode of meditation. For those who are more disciplined and wiser, there is the Avitakka/Avicara mode of meditation.
How does one practise that? Please provide details.
This question can never be answered. The scriptures tell us of only 14 people who have realized nibbhana by practising this method.  Few of them that come to mind are Bahiya Dharuciraya, King Pukkusati, King’s Minister Santhathi, Arahant Dabbamallatissa, and Bhikku Kumara Kashyapa.
Why is vipassana and samatha not required on the fourth path?
This answer is there within the above explanation. These few individuals came to panna vimutti, but to come to this they never did any kind of Jhana. They never had to do samatha or vipassana meditation. Within a matter of minutes, they achieved nibbana through **Dhamma Uddhacca Vigghahita Maanasan”.
To explain this Pali term…. Uddhacca  means the tendency to be high-minded (restlessness) - It arises because of high-mindedness. Uddacca remains as a cetasika and is removed only at the Arahant stage. Uddacca is the tendency to get at least irritated when not treated as expected. But it is to be noted that the levels of mana, uddacca, avijja that an Anagami has, are at much reduced level.
Uddhacca Vigghahita means the eradication of Uddhacca. This is the quickest way to remove all traces of the root causes - raga, dosa, and, moha. Or in other words Uddhacca Vigghahita  is the easiest way to remove lobha, dosa, and, moha (for akusala kamma), and alobha, adosa, and amoha (for kusala kamma).

@SapthaVisuddhi thank you for this answer. We have noted "freed by wisdom" as a key phrase that will find 18 suttas.

Bhikkhu Bodhi has a footnote about this, which I have decided to disagree with, for the sake of alternative view. However, in his footnote, he points out how there are three variations of this Pali text (PTS, Sinhala, Burmese), including 'dhammuddhaccaviggahitaṃ mānasaṃ' (which he agrees with, namely, 'manasa' as 'mind' or 'thinking') versus 'dhammuddhaccaviggahitaṃanā' (which I have decided to agree with). BB rejects the later because it would include the word 'conceit' ('ṃanā'), which he believes is suspicious. However, I have decided to disagree with BB and speculate 'ṃanā' is not suspicious because the other term in the phrase is 'uddhacca', namely, restlessness. The other word is 'viggahita', which means 'taken hold of, seized; seduced by'.
'Conceit' ('ṃanā') is the 8th fetter; 'restlessness' ('uddhacca') is the 9th fetter. Here, in the 4th path, the practitioner is a 'non-returner' ('anāgāmi') seized/seduced by two of the final fetters needed to be broken for arahantship. Thus, in this 4th path, the non-returner has already developed tranquility & insight but encounters a speed bump with the 8th & 9th fetters. But the non-returner settles the mind (citta), breaks the fetters and completes the path.
Since the sutta is strangely attributed to Ananda about arahants making declarations to him, which is even more bizarre, and since this sutta is both a one-off and has varied versions, personally, I would ignore & reject it. The sutta seems typical of the non-sense found in the Anguttara Nikaya.
Bhikkhu Sujato at Sutta Central might take an interest in this. I suggest to start this topic there.

Thanks. There is already a discussion thread at Sutta Central on this here.

Funny Brahmali agreed with my concluding comment, where he said: "I do not think such marginal ideas deserve much attention" . There is a 1st time for everything. :) Having read the posts at SC, I think my answer here is best, which seems to conform with the concluding comment that: "the case of Bahiya... because the sutta talks about attaining arahantship, not stream-entry". Bahiya, like the monk in MN 140, had probably already developed the 4th jhana thus was essentially mentally a non-returner (but not in terms of wisdom). Regards

When you read S.N. or A.N. You should connect sutta that come before or after together, too. Obviously, the sequence of everything in contexts are very important to understand tipitaka. This is a reason that why I often said that reciting&memorizing, just pāli, are better than reading, and especially better than reading the translated version.
I don't want to insult anyone. I just try to advise the one way path that intention-cetasika of bodhisatta choose to born to be then buddha force bikkhu to make it done for to be a perfect bhikkhu and for to be ariya (perfect person).
The Answer
Full answers already answered inside yugganaddhakathā of paṭisambihdāmagga, and nettipakaraṇa desanāhāravibhaṅga+nayasamuṭṭhāna. Also, you can use commentary, but you must recite and memorize tipitaka first because comment in commentary is over short, for the reader.
Connect with the previous sutta, Asubha Sutta.

Practitioner who hard to meditate, quickly/delayed access to insight = Development of insight preceded by meditating concentration. This practitioner's hindrances often arise between his meditation. He must inhibits hindrances before meditate an insight. So buddha said "Bhikkhu, you must meditate a concentration, bhikkhu who meditated a concentration, will access to insight (5 aggregates)".
Practitioner who easily to meditate, quickly/delayed access to insight = Development of concentration preceded by meditating insight. This practitioner's hindrances not often arise between his meditation. So he meditate easily.
Practitioner who quickly access to insight, easily/hard to meditate = Tranquility developed in tandem with insight. This practitioner turned to be pro of 1st and 2nd above. He meditating insight at pahāna-pariññā state (from 3 pariññā).
Practitioner who delayed access to insight, easily/hard to meditate = Practitioner who has to inhibit hindrances from mind when meditating insight.  This practitioner is not pro enough of 1st and 2nd above. He still meditating insight at tīraṇa-pariññā state. So he have to try more to meditate 1st, 2nd to be 3rd. See the advance detail in tipitaka paṭisambhidāmagga (somewhere, I have not read it done), and visuddhimagga understanding-part maggāmaggañāṇadassanavisuddhi-niddesa to (especially from indriyatikkhakāraṇanavaka-kathā to paṭipadāñāṇadassanavisuddhi-niddesa).

Vocabulary in sutta that connect it together:
Paṭipadā=Maggo sañjāyati.
Dhammuddhacca=Vipassanpakilesa.
(there are more word, but you should to recite&memorize&meditate from pali of them yourselves with the meditated teacher such as pa-auk teachers).

Are you saying that meditation comes easily for one who develops insight before concentration, because insight overcomes hindrances?

No, that is thai understanding tradition which not compatibility with the suttas' explanation in that vagga. Buddha explained about 5 indriya, so it is about power accumulation of whole 5 indriya. It is not about one help one such as paññindtiya (insight)  help samādindriya (concentration), because no way that the practitioner can meditate an insight, before his  hindrances overcome by concentration. So I quoted above that buddha
said "Bhikkhu, you must meditate a concentration, bhikkhu who meditated a concentration, will access to insight (5 aggregates)."

Moreover, I can completely say that thai meaning is a mistake that make reader confuse. A person who was the beginner of that definition was not tipitaka memorizer (he was anti-abhidhammist, who had a manpower in thai about more than 100 years ago in colony war period). This is not my idea even though not commentary idea, because the sequences of pali words and sutta force the memorizer, who reciting pali,  to understand like that.

OK. So, it is the opposite. It is easier in meditation practice, to cultivate concentration before insight or both in tandem, but it's harder in meditation practice, to cultivate insight before concentration? And what about the fourth path that I asked in my question? Where does that come in?

I wroted above "Practitioner who has to inhibit (samatha) hindrances (dhammuddhacca) from mind when meditating insight (vipassanā, especially taruṇa-udayabyañāṇa). "

How does the fourth path work? Please elaborate on the fourth path.

You are thinking and pondering about the dhamma you have experiencing

How does one practise that? Please provide details.

There is no explicit way to to do this. If you start thinking and pondering on the Dhamma then this happens.

Why is vipassana and samatha not required on the fourth path?

Both are required. If you do not do Vipassana you do not experience the Dhamma to think and ponder on. Either Samantha develops or through developing Samantha where you mind is calmed.

Did Bāhiya practise Vipassana and Samatha? Quote (Piya Tan): "The story of how Bāhiya Dārucīriya awakens by just listening to the Buddha as related in the (Arahata) Bāhiya Sutta (U 1.10) should be carefully examined: note especially how the Buddha skillfully calmed Bāhiya’s mind."

Bahiya had reached the 8th Jhana (atta samapatti) before meeting the Buddha. Thi is the highest form of Jhana.

I think that comy is almost certainly wrong here and that the 4th path probably refers to people who don't need to do much in terms of learning [pondering] or meditating [for lower attainments] and their mind rather quickly goes to the Deathless [destruction of taints; nibbananirodhadhatu; associated with cessation of perception & feeling] even from the lower jhanas as soon as there is an opening due to the maturity of their insight faculty, these are probably those who end up as released-by-wisdom-arahants lacking the arupa jhanas or as what they call dry-insight worker maybe.
I don't see what else it could be based on other sutta and i think the commentary theory has no basis at all in the sutta.
If one takes the first 3 types to be those whovdeveloped arupa jhana and 4th type as those who didn't then the 4-fold classification makes sense imo.

I wrote a formatted and detailed answer here on my blog, which I cut and paste below the blog post link (losing html formatting).
http://notesonthedhamma.blogspot.com/2021/08/an-4170-forum-question-how-does-4th-way.html
There are 4 permutations of samatha and vipassana, the order in which they're developed.
The 3rd permutations is the ideal scenario, where both are developed in tandem.
The 4th permutation, neither are developed, at first. But then:
Puna caparaṃ, āvuso, bhikkhuno dhammuddhaccaviggahitaṃ mānasaṃ hoti.
Another monk’s mind is seized by restlessness to realize the teaching.
Hoti so, āvuso, samayo yaṃ taṃ cittaṃ ajjhattameva santiṭṭhati sannisīdati ekodi hoti samādhiyati.
But there comes a time when their mind is stilled internally; it settles, unifies, and becomes undistractify-&-lucidifyd in samādhi.
Tassa maggo sañjāyati.
The path is born in them.
So taṃ maggaṃ āsevati bhāveti bahulīkaroti.
They cultivate, develop, and make much of it.
To answer the OP questions, two key points need to be understood.
ekodi and samadhi is code phrase indicating second jhana or higher (see MN 20, MN 119, and several others).
dhamma-uddhacca-viggahitaṃ
Uddhacca is referring to the 5 hindrance's restlessnness.
vigggahitam means trying to the ascertain the meaning.
So the meditator, in trying to ascertain the meaning of Dhamma when under the influence of the hindrance of restlessness (4th of 5 hindrances), fails. In other words, he's not doing vipassana successfully because he has insufficient samatha.
But later on, he develops second jhana or higher as indicated by the ekodi and samadhi markers, fullfilling requisite amount of samatha (see SN 46.2, samatha is nutriment for samadhi). Therefore the uddhacca restlessness is no longer a problem, and his Dharma investigation succeeds, his vipassana succeeds because his samatha is good enough.
Since the 4 permutations already covered the samatha preceding vipassanna, then this 4th case is unlikely to be that, and more likely to be having initially no samatha and vipassana, and later samatha and vipassana in tandem.
Conclusion on AN 4.170
So when one considers all 4 permutations, and all 4 attain a path that leads to arahantship, it's clear that samatha and vipassana both need to be present to sufficient quality to succeed, it's just that through inherent weakness in individual meditators, some may mature in samatha first or vipassana first, and not the case that the Buddha recommended one develop samatha before vipassana, or vice versa.
Also, if you study the formula for the four jhanas carefully, and the satipatthana formula carefully, you'll see that 3rd jhana (any of 4 jhanas would fulfill samatha)  includes both sati and sampajano (equivalent to pañña and vipassana). And within the satipatthana formula, which also includes sati and sampajano factors, the "vineyya loke abhijja domanassa" is a reference to one having subdued the 5 hindrances, the tough part of samatha training, and putting you right in the doorway of first jhana (which would satisfy samatha). In other words, satipatthana is embedded within jhana, and jhana is embedded within satipatthana. That's the Buddha saying samatha and vipassana is ideally developed in tanndem (  4 Jhānas ≈ 4 Satipaṭṭhāna ).

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text:
Is there a thought in Buddhism which stand for the thinker itself as a thought?
Usually our thoughts have a certain content or object, but in some way one can say that it is the person who has the thoughts. But is there also a mental thought involved of this thinker as a thought? How is this named in Buddhism? Is that 'ego', also as a thought possible? I hope it is clear what I mean....

Perhaps you're thinking of various words which are translated as "mind" or "consciousness".
I think it's said that the mind is aware of thoughts -- or if not "mind" then "consciousness of mental activity" ... in the same way that "eye consciousness" is aware of sights, and "ear consciousness" is of sounds.
Western philosophy has theories like "I think, therefore I am"; but I think that Buddhist doctrine includes statements such as, "I am not these thoughts, these thoughts are not mine, and are not me."
Because you're constantly aware of them, though (in the same way that a dog who is tied to a post will be constantly aware of the post), you might be inclined to view them as "me".

Or the word you're asking for may be "self-view" or "identity-view", which is a view (or thought) that the "self" exists. Or if it's not a fixed/permanent view, it might be called "pride" or "conceit". See ...

What are examples of identity-view? and
How are 'conceit' and 'identity-view' not the same?

... for some further answers about these topics.


text:
Buddhist view on past lives influencing the present
I seem to be making rather unusual choices in my life for unknown reasons. Like on a mere hunch or for some reason I gain interest in a strange topic. And later it turns out that these choices were exactly what I needed to have done to prepare for things that eventually happened. Is this addressed in the dharma? I make no claims about psychic powers or anything like that - I just wonder if it is merely coincidence.

Your question is not about whether past life actions influence present life circumstances. For that, see this answer and this sutta.
Rather, you are asking if your past life thoughts, affect your present life thoughts (or thought choices).
In a single lifetime, the answer is yes according to Dvedhavitakka Sutta.

"Whatever a monk keeps pursuing with his thinking & pondering, that
  becomes the inclination of his awareness. If a monk keeps pursuing
  thinking imbued with sensuality, abandoning thinking imbued with
  renunciation, his mind is bent by that thinking imbued with
  sensuality.

But does this cross into other lifetimes?
From the Nakhasikha Sutta, Samudda Sutta and Pokkharani Sutta:

"In the same way, monks, for a disciple of the noble ones who is
  consummate in view, an individual who has broken through [to
  stream-entry], the suffering & stress that is totally ended &
  extinguished is far greater. That which remains in the state of having
  at most seven remaining lifetimes is next to nothing: it's not a
  hundredth, a thousandth, a one hundred-thousandth, when compared with
  the previous mass of suffering. That's how great the benefit is of
  breaking through to the Dhamma, monks. That's how great the benefit is
  of obtaining the Dhamma eye."

When one obtains the Dhamma eye, and attains stream-entry, he would only have at most, seven remaining lifetimes. The Dhamma eye is explained as the ability to see firsthand and experientially, the impermanence of the five aggregates and dependent origination.
This is obviously an example in the Pali Canon that at least some thoughts or knowledge could cross over into the next life. In this case, it is the strong and irrevocable inclination towards the Dhamma in future lives, due to the opening of the Dhamma eye.
Also see this question and this answer.
Some say that child prodigies bring with them the strong inclinations of the immediate previous life, but I think that cannot be found in the scripture, and the Buddha would not bother to answer this (parable of the poisoned arrow, parable of the simsapa leaves, etc.).

The Buddha discouraged such ideas.

Having approached the brahmans & contemplatives who hold that... 'Whatever a person experiences... is all caused by what was done in
  the past,' I said to them: 'Is it true that you hold that... "Whatever
  a person experiences... is all caused by what was done in the past?"'
  Thus asked by me, they admitted, 'Yes.' Then I said to them, 'Then in
  that case, a person is a killer of living beings because of what was
  done in the past. A person is a thief... unchaste... a liar... a
  divisive speaker... a harsh speaker... an idle chatterer... greedy...
  malicious... a holder of wrong views because of what was done in the
  past.' When one falls back on what was done in the past as being
  essential, monks, there is no desire, no effort [at the thought],
  'This should be done. This shouldn't be done.' When one can't pin down
  as a truth or reality what should & shouldn't be done, one dwells
  bewildered & unprotected. One cannot righteously refer to oneself as a
  contemplative. This was my first righteous refutation of those
  brahmans & contemplatives who hold to such teachings, such views. AN
  3.61

Now when those ascetics and brahmins hold such a doctrine and view as this, ‘Whatever a person experiences, whether it be pleasant or
  painful or neither-painful-nor-pleasant, all that is caused by what
  was done in the past,’ they overshoot what one knows by oneself and
  they overshoot what is considered to be true in the world. Therefore I
  say that this is wrong on the part of those ascetics and brahmins. SN
  36.21

Friend, the Blessed One has said that pleasure and pain are dependently arisen. Dependent on what? Dependent on contact. If one
  were to speak thus one would be stating what has been said by the
  Blessed One and would not misrepresent him with what is contrary to
  fact; one would explain in accordance with the Dhamma, and no
  reasonable consequence of one’s assertion would give ground for
  criticism.
Therein, friend, in the case of those ascetics and brahmins, proponents of kamma, who maintain that pleasure and pain are created
  by oneself, and those who maintain that pleasure and pain are created
  by another, and those who maintain that pleasure and pain are created
  both by oneself and by another, and those who maintain that pleasure
  and pain have arisen fortuitously, being created neither by oneself
  nor by another—in each case that is conditioned by contact.
Therein, friends, in the case of those ascetics and brahmins,
  proponents of kamma, who maintain that pleasure and pain are created
  by oneself, and those who maintain that pleasure and pain are created
  by another, and those who maintain that pleasure and pain are created
  both by oneself and by another, and those who maintain that pleasure
  and pain have arisen fortuitously, being created neither by oneself
  nor by another—in each case it is impossible that they will experience
  anything without contact.
SN 12.25

Now what, monks, is old kamma? The eye ought to be viewed as old kamma, capable of being fabricated, willed & felt. The ear... The
  nose... The tongue... The body... The intellect ought to be viewed as
  old kamma, capable of being fabricated, willed & felt.. This is called
  old kamma. SN 35.145

I understand the others but disagree about the issue of contact. That was something believed at that time based on their understanding of the natural world. We have grown beyond that in natural science knowledge now. The first argument merely states thinking in that manner may affect contemplative thought. The second says we underestimate ourselves which is another "may" thing like the first. I dont understand the last one. If you could explain that one I would appreciate it. thanks!

The last one seems to say to not go beyond the sense organs when considering old kamma because whatever occurred in the past is arising in the present.

OK. I see what you're saying. But how is that an answer? It just says "dont worry about it. worry about now." I can't help but think they are just avoiding the issue.