Yoga is based on the Samkhya philosophy, and in its terminology, the mind is called Citta.
The soul is called Purusha. In Yoga, "self" refers to Purusha, not the body or the mind (Citta).

The "waves of thought" that appear in the Citta (mind) are called Vrttis. The etymology is "whirlpool."
If you were to compare it, the lake would be the Citta (mind), and the waves would be the Vrttis.

The purpose and function of Yoga can be summarized in the following two sentences:
"Yoga is the cessation of the activities (functions, states) of the mind" (Yoga-Citta-Vritti-Nirodhah).
"Then, the observer dwells in their own true nature" (Tada Drashtuh Svarupe Vasthanam).
The "Yoga Sutras" written by Patanjali explain these two sentences.

The Citta (mind) has three states called Gunas.
- Tamas: The state of darkness. Beasts and fools. Inertia.
- Rajas: Activity. An active state.
- Sattva: Stillness. Calmness. Clarity.

Not only the mind, but all of nature and the universe are composed of these three states. The material that existed before the mind, nature, and the universe had these three states is called Avyakta (something that has no definition, something that is not individually separated). The highest thing composed of these three materials is called Mahat (intellect, cosmic intelligence), and human intellect is a part of it, which is called Buddhi (cognition).

Manas (mind) collects impressions and sends them to Buddhi (cognition). Then, Buddhi determines what they are.
Egoism (Ahamkara) is born through Buddhi (the ability to determine). If Buddhi is "movement," then Ahamkara is "counter-movement."

Components of the Citta (mind):
- Buddhi (cognition)
- Ahamkara (egoism)
- Manas (mind)

Perception occurs in the following order:
1. Input signals from the external world are transmitted through the sensory organs (eyes and ears) to the "organs" (Indriyas) in the brain.
2. The brain's "organs" (Indriyas) transmit these input signals to the Citta (mind).
3. In the Citta (mind), Manas (mind) carries the impressions to Buddhi (cognition), and Buddhi determines the impressions.
4. Egoism (Ahamkara) is born through the reaction of Buddhi (the ability to determine).
5. These are passed on to Purusha (soul), and the object is recognized.

The group called "internal instruments" (Antahkarana):
- Organs (Indriyas)
- Manas (mind)
- Buddhi (cognition)
- Egoism (Ahamkara)
These are various processes that occur in the Citta (mind).

The Citta (mind), which is an instrument, releases "thoughts" (Vrttis) using the energy obtained through food. Therefore, the Citta (mind) is not an intelligent entity. However, the Citta (mind) appears to be intelligent because Purusha (soul) is behind it.

Three proofs:
1. Direct perception, Pratyaksha. Something that is obvious through seeing and feeling. For example, the existence of the world.
2. Inference, Anumana.
3. Perception by Yogis who have seen the truth, Aprta. The knowledge of Aprta comes from the individual themselves. The literal meaning is "reached."

Various Vrttis (waves of thought):
- Vikarpa: Linguistic deception. Unreal thoughts. One is easily deceived if the Citta (mind) is weak.
- Dreams: The Vrttis (waves of thought) during sleep become dreams.
- Memory, Smrtih. Memory is when the subject's Vrttis (waves of thought) return to consciousness through a trigger such as words.

What remains after the Vrttis (waves of thought) disappear is the impression (Samskara, Sankara, Karma).
Impressions (Samskaras, Sankaras, Karma) are thoughts in the subconscious.
When there are many impressions (Samskaras, Sankaras, Karma), they become habits and shape personality.

The effort to keep the Vrttis (waves of thought) completely suppressed is "practice."
The state of being suppressed is called Vairagya (detachment).
Vairagya (detachment) prevents the Citta (mind) from being dominated by Vrttis (waves of thought). It also means non-attachment.
When Vairagya (detachment) is achieved, the nature of Purusha (soul, true self) appears.

The mind (Citta) is composed of Sattva but is covered by Rajas and Tamas. It can be purified through Pranayama, which removes the coverings. This allows the mind (Manas) to concentrate. Concentration is called Dharana.

Dharana requires Pratayahara. Pratayahara is the ability to direct the mind (Citta) to and from the nervous system at will. Literally, it means "drawing in."

When Dharana is achieved, the concept of time disappears. Therefore, when the past and present become one, it is said that the mind is in Dharana.

Continuing Dharana is called Dhyana (meditation). When Dhyana deepens further, and the form of the object of meditation disappears, leaving only the meaning, it is called Samadhi.

Samadhi is divided into two types:
1. Samprajnata Samadhi. This is the acquisition of power over nature. It is called "Samadhi with seed." It is a Samadhi that produces reincarnation.
2. Asamprajnata Samadhi. This is the Samadhi that leads to liberation. It is called "Samadhi without seed." It is a Samadhi that eliminates the seeds of reincarnation.

■Types of Meditation and Samprajnata Samadhi
At this stage, impressions (Samskaras) remain, and the mind is not yet completely purified.

1. Savitarka Samadhi. "Savitarka" means "with inquiry." Even with the acquisition of power, liberation is not attained. It is a worldly, futile, and empty Samadhi that seeks pleasure. This is an old teaching. It involves the simultaneous occurrence of word (Jada), object (Arta), and knowledge (Jnana).
2. Nirvitarka Samadhi. This means "without inquiry." It is a meditation that contemplates the true nature of things, outside of time and space. There is no word (Jada) or object (Arta), only knowledge (Jnana).
3. Savichara Samadhi. This means "with discrimination." It is a meditation that contemplates things as existing within time and perception.
4. Nirvichara Samadhi. This means "without discrimination." It is a further development of Savichara Samadhi. It is a meditation that contemplates the subtle elements, excluding time and space.
These two are variations of the previous stages, Savitarka and Nirvitarka Samadhi, where the object of contemplation is changed to more subtle things (Tamasutra, Citta, Ego).
When Nirvichara Samadhi is combined with purity, one attains Ritambhara Prajna, a wisdom filled with truth. A person who reaches this stage is called a liberated sage (Jivanmukta). "Jivan" means living, and "Mukta" means liberated.
5. Sananda Samadhi. This is a blissful Samadhi. It is a meditation performed in a state of freedom from activity and inertia.
6. Sasmitara Samadhi. This is a state where one feels "as if they have lost their body." The soul, which naturally merges with nature in this state, is called Prakriyara, but it is not yet liberation.

■Meditation for Asamprajnata Samadhi, which leads to liberation
As soon as a thought arises, it is eliminated, and no thought is allowed to enter the mind. This creates a vacuum state of the mind, demonstrating the greatest control over the mind.
(Incorrect meditation can cover the mind with Tamas. Be careful not to mistake the act of making the mind inactive as emptying the mind, as this is due to ignorance.)

In meditation before Asamprajnata, the mind's Vrittis (thought patterns) are suppressed through concentration.
However, in Asamprajnata, the "seeds" that create the mind's Vrittis disappear. This is why it is called "becoming seedless." The seeds that produce endless reincarnation disappear.

■Classification of Samadhi with and without seed
Saviya Samadhi: Samadhi with seed. This includes Samprajnata Samadhi and Savikalpa Samadhi.
Nirbija Samadhi: Samadhi without seed. This includes Asamprajnata Samadhi and Nirvikalpa Samadhi.

■Samyama
When Dharana (concentration), Dhyana (meditation), and Samadhi are achieved simultaneously, it is called Samyama. Samyama gives rise to Siddhis (spiritual powers). By delving deeply into the object or the concept of the object, the object reveals its secrets.

■Dharma Meghah Samadhi (Samadhi of the Cloud of Dharma)
Dharma Meghah: This means that all virtues are present within it.
This samadhi occurs when even the desire to "become" something has disappeared.
The feeling of seeking God is achieved through "non-attachment." Up to a certain point, effort is continued, but when one reaches this point, effort ceases and becomes effortless. And then, one knows God. A Jivanmukta (liberated being) appears.
All suffering (desires) and karma end.

■Nirbijah Samadhi
In "Integral Yoga" (by Swami Sachidananda), this is considered the highest samadhi that comes after Jivanmukta (enlightened being), and Asampragnata Samadhi is only briefly mentioned.
On the other hand, in "Raja Yoga" (by Swami Vivekananda), this is described as a general final state. It is written vaguely, and it is not explicitly stated that this is the highest state. Earlier in the book, Asampragnata Samadhi is introduced as leading to ultimate liberation.
Therefore, the relationship between Nirbijah Samadhi, Asampragnata Samadhi, and other samadhis such as Saranda Samadhi and Sasumita Samadhi is unclear.

■Karma Arsha (Bag of Karma)
All karma, including past lives, are accumulated in the Karma Arsha (bag of karma).

■Three Types of Karma
- Prarabdha Karma (Survival Karma):
Karma that is drawn from the Karma Arsha (bag of karma) to be experienced in this life. The body is chosen based on this karma.
This explains unexpected events. For example, getting injured by accidentally bumping into a rock.
- Sanchita Karma:
The total sum of all past karma.
- Agami Karma:
New karma. Karma that is intentionally and knowingly performed. For example, intentionally kicking a rock and injuring your toe.
Jivanmuktas (liberated beings) are not affected by Agami Karma.

■God
Many souls who failed to let go of all their powers, but almost succeeded, are called "God."
The Sankhya philosophy states that there is no absolute, single God beyond that. While some yogis believe in an absolute God, even in those cases, they refer to the many souls who failed as God.
Souls who do not desire the status of God or the status of ruler of the cycles of time attain liberation.

■Supreme Ruler
Ishvara (Supreme Ruler) is a special Purusha (soul) with infinite knowledge. According to the Vedas, Ishvara is the creator of the universe.
However, for yogis, Ishvara is not the creator of the universe, but the name given to the infinite knowledge and all-powerful God.

■Enlightenment
"Enlightenment" is true religion, and everything else is merely preparation.
Listening to sermons, reading books, or following logic are just preparations, not religion.

■Egoism
Egoism is the belief that the instrument is the one who is seeing. This is the state of "ignorance."
The Purusha (soul) is the seer, and the mind (Chitta) and sense organs (Indriyas) are the instruments of seeing.
Egoism arises from the misunderstanding that the mind (Chitta) and sense organs (Indriyas) are oneself.
No one can cause pain to the Purusha (soul). The Purusha (soul) transcends the mind (Chitta), and whether the mind (Chitta) is happy or sad, the Purusha (soul) remains unchanged. However, due to ignorance, we believe that we are the mind (Chitta) and mistakenly believe that "we feel pleasure and pain."

■Discussion and Conclusion
- Argumentative things (Vada)
- Definitive things (Siddhanta)
One starts with discussion (Vada). However, after reaching a conclusion, one enters the realm of Siddhanta (Siddhanta) and strengthens it. Yogis have already gone through the stage of discussion. Yogis do not engage in discussion (Vada) because they desire something beyond the mind (Chitta).

■Decomposition and Control of Impressions (Samskaras, Sankaras, Actions)
What remains after the Vrittis (waves of thought) disappear are impressions (Samskaras, Sankaras, actions). Impressions (Samskaras, Sankaras, actions) are sleeping in the mind (Chitta). Impressions (Samskaras, Sankaras, actions) are the root and cause. It is necessary to completely decompose and control the impressions (Samskaras, Sankaras, actions).
It is relatively easy to recognize the mind (Chitta) and Vrittis (waves of thought). However, impressions (Samskaras, Sankaras, actions) are deeply asleep and working in the subconscious.
By controlling the root of the subtle causes before the Vrittis (waves of thought) appear in a gross form, it is possible to control the seeds of impressions (Samskaras, Sankaras, actions) and burn them away.
Refined impressions (Samskaras, Sankaras, actions) cannot be burned away through meditation. By decomposing the impressions (Samskaras, Sankaras, actions) into their causes, and decomposing the cause, which is Asmita (egoism), the impressions (Samskaras, Sankaras, actions) disappear along with them.

First, impressions (samskaras, traces, actions) surface through meditation. Then, you can determine whether to express them as actions (although you would likely choose not to). Next, continuing the meditation, you discover that the cause lies in asmita (egoism). By transcending the mind into a higher state of samadhi, this asmita (egoism) disappears. When asmita (egoism) disappears, all the impressions (samskaras, traces, actions) within it also disappear.

■ Subtle Micro-Particles (Tamas)
Our minds constantly emit these. Places where people worship God are filled with good tamas.

■ Four Stages (parvani) of Guna (qualities: sattva, rajas, tamas)
- "Defined things (visesa)": The coarse elements that we perceive through our senses.
- "Undefined things (avisesa)": Tamas.
- "Things that are only hinted at (linga-matra)": Buddhi (the ability to determine, intellect). The first manifestation of nature.
- "Things that have no indication (alingani)":

■ Purusha (Soul)
Omniscient, omnipotent, omnipresent. It is not the mind. It is not matter. Because it is neither nature nor anything else, it does not change.

■ Prakriti
The basic substance that constitutes this world. Prakriti is the material principle in relation to Purusha, the pure spiritual principle.
Purusha is the "observer," while everything else that is not Purusha is Prakriti, the "observed."

■ Synonyms of Purusha
In Samkhya philosophy, the word Purusha is used, but in Vedanta, the words Brahman and Atman are used.
- Samkhya philosophy: Purusha exists both within individual beings and simultaneously is the omnipresent soul. Ishvara (the supreme ruler) is also one of the Purushas.
- Vedanta: Brahman is the omnipresent absolute existence. Atman is the individual soul. However, Vedanta ultimately leads to the conclusion that Brahman and Atman are one.
So, although the words are different, they seem to be describing similar things.

■ Citta (Mind) and Purusha (Soul)
Citta (mind) sees the external world as the subject. Or, it is seen by Purusha (soul) as the object.
Purusha (soul) is always the subject.
"The self" is, in a sense, both the witness and the actor, but in reality, it is the witness. If you lose sight of the "real" thing, you become the actor.

■ Yoga Practice and Citta (Mind)
Yoga practice is performed by "Citta (mind)." Purusha (soul) does not need yoga practice. Purusha (soul) should be left alone. It is the ego (self) that needs yoga practice. The teachings are given to the ego (self).
By freeing the lower self, Citta (mind), from the actions of the ego, the radiance of Purusha (soul) increases and it can "rest."
As relaxation increases, the yogi can rest not only when Citta (mind) is not moving, but even when Citta (mind) is moving. The yogi "enjoys" actions.
The scriptures are for the purpose of knowledge and understanding. The truth for the ego is found in everyday life: learning to be selfless and living a dedicated life. Actions are performed for others, and in doing so, Citta (mind) finds peace.

■ Jivanmukta (Enlightened Being) and Guna (qualities: sattva, rajas, tamas)
When one becomes a Jivanmukta (enlightened being), the gunas complete their purpose and cease their function.
Until then, the purpose of the gunas was to provide experience to Purusha. When that purpose is gone, the gunas return to their original state of Prakriti. When the gunas are not manifesting, they are in the state of Prakriti. When Prakriti manifests, it is called a guna. When that manifestation ends, Prakriti remains as Prakriti, at rest. It is completely purified, and "pure consciousness rests in its own pure nature."

Here, the goal of yoga, as first stated by Patanjali, is achieved: "The cessation of the fluctuations of the mind (Yoga-Chitta-Vritti-Nirodhah)," and "then the experience of the true Self (Tada Drashtuh Svarupe Vasthanam)."

"The cessation of the fluctuations of the mind (Yoga-Chitta-Vritti-Nirodhah)."
"Then the observer abides in his own true nature (Tada Drashtuh Svarupe Vasthanam)."

The following is from:
"Raja Yoga" (authored by Swami Vivekananda)
"Integral Yoga" (authored by Swami Sachidananda)