People of Advaita sect believe that Atman never remains locked or trapped IN the body. The same thing has been said by many hindoos in quora as well. (They are followers of advaita).
If what the advaitins believe is true, then what exactly is dehi? In the Bhagavad-gita it has been said that dehi dwells within the body and keeps changing bodies like old clothes. If dehi is not Atman, then what is it? Need an answer from both dualistic (vaishnava) and monistic (advaita) point of view.
Bhagavad Gita is regarded high from Advaita &/or Vaishnava school of thoughts. This answer is from that perspective.
According to it, Dehi (embodied one) transgresses from one body to another, upon death:
वासांसि जीर्णानि यथा विहाय, नवानि गृह्णाति नरोऽपराणि। तथा शरीराणि विहाय जीर्णा, न्यन्यानि संयाति नवानि देही।।
BG 2.22 - As after rejecting worn out clothes a man takes up other new ones, likewise after rejecting worn out bodies the 'embodied one' unites with other new ones.
Almost same description is given for Ishvara as well:
शरीरं यदवाप्नोति यच्चाप्युत्क्रामतीश्वरः। गृहीत्वैतानि संयाति वायुर्गन्धानिवाशयात्।।
BG 15.8 -- When the Body is received and also when given up, the "Master" (ishvara) carries all these [6 senses]; Same as wind transporting smell.
From these 2 verse, we can infer that the Dehi is the consciousness/intellect(Buddhi) or Purusha, which controls the senses + mind like a master.
It's higher in order than the mind, but lower than the Atman (or ParamAtma):
इन्द्रियाणि पराण्याहुरिन्द्रियेभ्यः परं मनः। मनसस्तु परा बुद्धिर्यो बुद्धेः परतस्तु सः ।।
BG 3.42 — Senses are said to be beyond [physical body]; mind (mann) is beyond senses; intellect (buddhi) is even beyond Mind; "That" (Atma) is even beyond intellect.
I don't know from vaishnavite perspective but I can answer advaitic perspective on this.
From Advaitic perspective too it's Atman that keeps changing body. Atman here is Ego self or 'I' ness.
In Advaita Atman is not the ultimate reality. Yes it is subtler than body and mind and the senses but the argument of Advaita is if you are aware of some thing existing (here Atman) then the one being aware of its existence should be even subtler.
Here is where Bhraman comes in to picture. Brahman is a viewer or perciever of this and all the other world. There ofcourse is atman and the mind and the body and all the struggles and the ascends and descends of it in life and after it but the one who is real the Brahman is always untouched by it because he just sits there and observes everything talking place.
Then to step it up we can say that this world is made of Brahman taking different forms. The body is Brahman, the mind is Brahman, the soul is Brahman the vital forces is Brahman, the Virat Swaroop is Brahman and yet the One is detached and watching all this is also Brahman.
Atman or ego or the Iness is one of the attachments we drop towards the path of self realization, if we are dropping something with Neti Neti, then it can not be the ultimate truth.
I would highly recommend reading Panchadasi if you want a comprehensive understanding of Advaita.
Atman(solo soul) is also ignorance, Only Param atma(Super soul) is real and called Kshetragya or Dehi or Purush.
Kshetrajna (Devnagari: क्षेत्रज्ञ/Purush/conciousness) means the One who knows of the body, soul, spirituality, conscious principle in the corporeal frame while everything else is Kshetra(or Prakriti)
https://en.wikipedia.org/wiki/Kshetrajna
The Kshetra or the field refers to the body which is material, mutable, transitory and perishable, the Kshetrajna refers to the conscious knower of the body who is of the same essence as Knowledge, immutable, eternal and imperishable, the knower of the body is the soul residing in the body. Kshetra is Prakrti or matter which is insentient, and the knower of the Kshetra is the Purusha who is sentient. True knowledge is knowing and understanding both these two factors, the insentient and sentient. The knowledge of Prakrti only, is called the Apara Vidya or Lower knowledge, and that pertaining to the Purusha is called the Para Vidya or Higher knowledge. in the Bhagavad Gita, Arjuna is told that the distinctive nature of God is eight-fold constituted by the five primordial elements, mind, intellect and the ego-sense, but that is the lower nature which is inferior, impure, troublesome, whose essence is bondage; the higher nature, which is the pure essential nature of God, is the higher living being, the Kshetrajna, the field-knower, the cause leading to the assumption of vital force by which the world is penetrated and upheld
God is 8 fold:-
5) elements(earth+water+fire+air+space)
6) Sun(intellect)
7) Moon(mind)
8) Consciousness(or Purush or Dehi)
or the 8 grahas in Hindu astrology(where 9th planet ketu(or dragon tail) is not a planet but a shadow)
Ahamkaar of body(ego) or Atman is ignorance born out of Aham(I) when Dehi/Kshetragya identifies himself with body or some limited self is the one that changes body after death
https://en.wikipedia.org/wiki/Para_Vidya
Vedanta affirms that those who gain the knowledge of the Self attain kaivalya, they become liberated, they become Brahman. Kaivalya is highest state of moksha
I-i-15-17. Hanuman: Rama, sages speak differently: some say there is only one kind of liberation. Others say it can be got by worshipping your name and by the Taraka mantra at Kashi. Others speak of Sankhya-Yoga and Bhakti-Yoga, the enquiry into Vedanta-Vakyas etc.
I-i-18-23. Rama: Liberation is of four kinds: Salokya, Sameepya, Sayuja, Sarupya etc. But the only real type is Kaivalya and permanent, rest all are temporary
Hence Vedanta focuses on self enquiry and self realization and not worshipping as worshipping means daulity but reality is non-dual as per Kaivalya Moksha
Saunaka, having asked – कस्मिन्नु भगवो विज्ञाते सर्वमिदं विज्ञातं भवतीति (" Revered Sir, what is that by the knowing of which all this becomes known? "), - was told by Angiras that –
द्वे विद्ये वेदितव्ये इति ह् स्म यद्ब्रह्मविदो वदन्ति परा चैवापरा च | तत्रापरा ऋग्वेदो यजुर्वेदः सामवेदोऽथर्ववेदः शिक्षा कल्पो व्याकरणं निरुक्तं छन्दो ज्योतिषमिति | अथ परा यया तदक्षरमधिग्म्यते || - (Mundaka Upanishad I.i.3-5) there were two different kinds of knowledge to be acquired – 'the higher knowledge' or Para Vidya (Sanskrit: परा विद्या )and 'the lower knowledge' or Apara Vidya. The lower knowledge consists of all textual knowledge - the four Vedas, the science of pronunciation etc., the code of rituals, grammar, etymology, metre and astrology. The higher knowledge is by which the immutable and the imperishable Atman is realized, which knowledge brings about the direct realization of the Supreme Reality, the source of All. The knowledge of the Atman is very subtle; it cannot be obtained out of one’s own effort; the Atman cannot be intuitively apprehended by mere intellectual equipments. Thus, Angiras draws the distinction between the way of knowledge and the way of realization, as between opinion and truth. For understanding this for realizing the Reality the aspirant must seek a teacher. The teacher who has already realized his identity with the Atman alone can impart this much sought-after wisdom on the strength of his own experiences
A human being is blessed with the faculty of self-knowledge which is Apara Vidya or logical reasoning and also with the faculty of understanding and self-awareness which is Para Vidya or quantum logic. Para Vidya is defined as the intuitive vision of non-duality;[5] it is the transcendental knowledge which is beyond all limits of knowledge, experience and reason, which is, beyond intellect, mind and sense. The Absolute, which is Truth, which is Reality, is neither an expression nor a reflection of itself; it is non-dual being devoid of otherness, and it cannot be an object of knowledge in the ordinary sense as it surpasses the intellect in subtleness. Knowledge is truth and truth is correspondence of an apprehension with its object. It is the intellect which moves within the sphere of duality resulting in delusion, wrong identification etc. Para Vidya is the intuitive level of vidya that stems from a unity, and manifests as a vision, manifests as an experience.
The vision of the Nirguna Brahman is gained through Para Vidya, it is the highest of all knowledge
> The method of self-realization involves sravana , manana and nididhyasana , and not rituals.
Note: Study about https://en.wikipedia.org/wiki/Ramana_Maharshi for understanding Kaivalya Vedanta further
Advaita school identifies the dehi with the linga sarira or subtle body.
MARWARI DEVOTEE: "Who is this 'I' that says, 'O Lord, I am Thy servant'?"
MASTER: "This is the lingasarira, or embodied soul. It consists of manas, buddhi, chitta, and ahamkara."
DEVOTEE: "Who is the embodied soul?"
MASTER: "It is the Atman bound by the eight fetters. And what is the chitta? It is the 'I consciousness' that says, 'Aha!'"
The Gospel of Sri Ramakrishna, The Master in Various Moods, October 2, 1884
This is what Ramanuja says in his commentary of the Gita verse posted below.
There was never a time when I did not exist, nor you nor any of these kings of men. Nor will there be any time in future when all of us shall cease to be.
Gita 2.12
Indeed, I, the Lord of all, who is eternal, was never non-existent, but existed always. It is not that these selves like you, who are subject to My Lordship, did not exist; you have always existed. It is not that 'all of us', I and you, shall cease to be in future, i.e., beyond the present time; we shall always exist. Even as no doubt can be entertained that I, the Supreme Self and Lord of all, am eternal, likewise, you (Arjuna and all others) who are embodied selves, also should be considered eternal.
Sri Ramanuja Gita Bhasya translated by Swami Adidevananda
The above post suggests that Vaishanvas also think of Jivas as embodied selves. The difference between the Advaita idea and the Vaishnava idea is that the former thinks that the perception of difference between the jivas and Supreme Spirit is due to ignorance while Vaishnavas think that the perception of difference is real.
