If it's difficult and complicated, it's not Buddhism.
Get to the core and find your center!

“Can’t we simply and clearly understand the core of the 2,600-year-old Buddhist doctrine?” Kwak Cheol-hwan, author of “All About Buddhism,” “This is the Core of Buddhism,” and “Encyclopedia of Time and Space Buddhism,” has clearly organized the key doctrinal trends and conceptual points of 2,600 years of Buddhism to convey this one core of “Buddha’s Teachings.”
All dry and difficult theoretical explanations were eliminated, and only the scriptures that are absolutely necessary and accurate for understanding the doctrine were cited, so that only the core of complex doctrines were described in an easy and accurate manner.
This is a proper introduction to Buddhism that provides a central point of study for beginners who are new to Buddhism, as well as for Buddhists who are tired of various commentaries and scriptures, and penetrates the core of Buddhist doctrine.

The basic framework of Buddhism is to move from suffering to the cessation of suffering, from discrimination to non-discrimination, and from mental instability to stability.
The entire development from Chapter 1 to Chapter 4 of this book is a learning process to discipline and purify the mind and achieve stability.

--- p.4, from the “Introduction”

The body is 'here and now', but 'thoughts' leave here and go somewhere, creating all kinds of discrimination.
Even though our thoughts seem to go to many places, they only go to two places: the past and the future.
Going to the past creates regret and resentment, and going to the future creates anxiety and worry.
If your thoughts wander to the past and future, immediately notice them and practice consistently focusing on the 'now'. This will gradually lead to stability.
In the ‘now’ where the beginning and end are disconnected, there is no room for delusion to enter.

--- p.5, from the “Introduction”

Therefore, the Nikayas and Agamas are a mixture of teachings that were directly preached by Gautama Buddha and those that were not.
This is an inevitable consequence of the history of Buddhism that compiled the sutras.
Therefore, when studying early Buddhism, we must understand and approach the core teachings of the Nikayas and Agamas.
Chapter 1 of this book Early Buddhism (2.
The contents of the teachings and practices are a brief explanation of the main points of the teachings that are repeatedly expounded in the Nikayas and Agamas.

--- p.18, from “Chapter 1 Early Buddhism”

Siddhartha clearly understood the truths of suffering, the truth of the cause of suffering, and the truth of the cessation of suffering, and repeatedly practiced and attained the truth of the path, and realized the 'wisdom of the complete cessation of all defilements' and became Buddha.
This wisdom is called 'Nujinmyeong'.
As the Buddha said, “Bhikkhus, as in the past, so now I teach only suffering and the cessation of suffering” (Samyutta Nikaya 22:86, Anuradha), Buddhism begins with suffering and ends with the cessation of suffering, that is, nirvana.
Since the Four Noble Truths are the only path from suffering to nirvana, these Four Noble Truths are the beginning and the end of early Buddhism.
Therefore, it is said, “Just as all the footprints of animals are included in the footprints of elephants, all teachings are included in the Four Noble Truths” (Madhyamakagamma Sutra, Volume 7, “Symbolic Sutra on the Traces of Images”).

--- p.26, 「Chapter 1 Early Buddhism, 2.
From “Teachings and Practice”

Therefore, the six senses are actions that need to be extinguished, but the six senses are not actions that need to be extinguished.
The extinction of the six senses, that is, the extinction of the function of perception, is wood, stone, or death.
In the twelve links of dependent origination, it is said that ‘when name and form cease, the six senses cease, and when the six senses cease, contact ceases’, which means that the function of the six senses that discriminate ceases, not that the function of perception ceases.
What arises from the ignorance of the twelve links of dependent origination are the six senses, not the six sense organs.
An Arahant is a saint who has not extinguished the six senses, but has extinguished the six sense bases.

--- p.54~55, 「Chapter 1 Early Buddhism, 2.
From “Teachings and Practice”

Without this insight, Abhidharma is meaningless.
Because Abhidharma is not an exploration of external objects, but an internal observation that breaks down one's own consciousness into its constituent elements, and constantly notices the arising and passing away of those elements at this very moment, thereby penetrating into their impermanence, suffering, and non-self, thereby eliminating greed, anger, and foolishness.

--- p.112, 「Chapter 2 Sectarian Buddhism, 1.
From “The Meaning of Law”

The most important phrase in this sutra is 'Jo-gyeon-five-skandhas-gong-il-gae ...
'Seeing through the emptiness of the five aggregates' means seeing through the state of the five aggregates, which successively give rise to all kinds of greed, discrimination, and attachment, to be cut off, and reaching non-discrimination.
In other words, the function of the five aggregates has been extinguished and the state of emptiness without discrimination has been reached. This is similar to the state of Zen Buddhism, where one sees through and sees the Buddha nature that one originally possesses.

--- p.137, 「Chapter 3 Mahayana Buddhism, 1.
From “The Core Ideas of Mahayana Buddhism”

This dichotomy of distinction and opposition arises from language.
But this is not a defect of language, it is the nature of language.
Language itself is dichotomous.
This is because the function of language is to distinguish between objects or concepts and to name each object.
However, since humans think in language, dichotomy is also a characteristic of thought.
All existence has no boundaries to begin with, but we divide it through thought and name it with language to distinguish it.
Therefore, all concepts that we perceive as distinct through language and thought are merely boundaries of fiction.
Yongsu argues that since 'existence' itself cannot be expressed in language, all fictional concepts must be denied and repudiated.
〈Jungsong〉 is not a verse that advocates a theory with a certain system, but rather a verse that repeatedly negates negations in order to break down the two-part distinction and fixed ideas.
If you assert something positively rather than negatively, the assertion itself (because it is expressed in language) can be subject to criticism due to the fictitious nature of language.

--- p.140~141, 「Chapter 3 Mahayana Buddhism, 2.
From “The Flow and Branches of Mahayana Buddhism”

The essence of Vijñāṇaṇa is often said to be 'the absence of consciousness and the absence of boundaries.'
That is, 'there is only a mental activity and no object.'
However, we must not deny the object of the five senses, that is, the object that exists outside now.
Then the perception function does not work.
Any perceptual process requires three elements:
One is the sense organs, two are real external objects, and three are the perceptual function of organizing and interpreting the signals received from the sense organs.
Therefore, if the object itself is denied, the perception process does not occur.
Then it is inanimate.
The object [realm] that is denied in 'no realm' is a fictional object created by imagination and an object that the five previous consciousnesses have distinguished as 'good/bad' under the influence of the manas-vijnana and alaya-vijnana.
These distinctions are not objectively real, but are all fictions created by the mind.

--- p.156~157, 「Chapter 3 Mahayana Buddhism, 2.
From “The Flow and Branches of Mahayana Buddhism”

Likewise, the saying, ‘Everything is created solely by the mind’ means that all things, including illusions, imagination, and the discrimination of the five senses, are all created by the mind, not that the objects of the five senses themselves are created by the mind.
Mountains and seas, trees and grass, flowers and butterflies, etc. are not created by the mind.
However, each person who sees them has different thoughts and feelings, and those thoughts and feelings are created by the mind.

--- p.157, 「Chapter 3 Mahayana Buddhism, 2.
From “The Flow and Branches of Mahayana Buddhism”

Mindlessness does not mean that there are no thoughts, but that one does not leave thoughts and is not attached to or bound by them.
So, it is said, 'I am in my thoughts but I am not thinking.'
This absence of thought is the perfection of wisdom, that is, Prajna Paramita.
This wisdom is ‘the wisdom of non-attachment’ and ‘the wisdom of non-discrimination.’
Even if you think about something and see, hear, feel, or know something, you are not bound by it and are always free, and you are not dragged around by the binary concepts of existence and non-existence, pleasure and suffering, birth and death, love and hate, happiness and unhappiness, etc. This is no-thought.

--- p.216, Chapter 4, Line 3.
From “Shinsu and Hyeneng”

The phrase "One should not be bound by anything and give birth to one's mind" from the Diamond Sutra is often quoted and comes from Huineng's sermons.
So, ever since Bodhidharma transmitted the 《Nengga Sutra》 to Hye-ga, this sutra has been passed down as the fundamental sutra of Seon Buddhism, and after Hye-neng, the 《Diamond Sutra》 became the fundamental sutra.
Hye-neng said that Zen is when one's pure nature is always at ease, when one's mind is stirred and moved within an object, and when one's mind is always upright, whether walking, staying, sitting, or lying down.
Hye-neng's method of goodness is sudden enlightenment and seeing one's own pure nature in an instant.

--- p.217, 「Chapter 4, Line, 3.
From “Shinsu and Hyeneng”

Just as the word mango is a tool for pointing to a mango, not the mango itself, so the word enlightenment is a tool for pointing to enlightenment, not enlightenment itself.
Words and names are merely thoughts given to an object or state, not the object or state itself, so all talk about enlightenment can only be expedient.
So, to those who seek Buddha outside, he warns, "The mind is Buddha," and to those who are obsessed with it, he warns, "It is neither mind nor Buddha," and to those who do not need to talk about mind and Buddha, he says, "It is nothing."
To climb up to the roof, you need a ladder, and to cross the stream, you need to step on stepping stones. However, Mazu was worried that if he was fixated on the ladder and stepping stones and was thinking about how to use them, he would fall off the ladder and fall into the stream.

--- p.224~225, 「Chapter 4, Line, 4.
Among the "Majo world and the Seokdu world"