The subtle body consists of sattva and rajas (three guṇa's) aspects of the five elements.

The subtle body is made to experience division, in the form of all kinds of experiences, especially pleasure or pain. Furthermore, it is programmed to work out and create karma, by directing actions of the body in the world, and thus to experience the apparent reality of an apparent life, which leads to reincarnation of the subtle body in a next life.

The subtle body is not named 'subtle' for nothing. It is invisible to the senses. The most important function is also the most refined: the intellect (buddhi) in the inner instrument (antaḥkaraṇa). The intellect is subtle enough to let knowledge do its work, so that ignorance is removed, so that knowledge can shine in the subtle intellect. The intellect in the subtle body is the key to freedom. In this way, the subtle body is also designed as a possibility for complete and correct self-knowledge and therefore as a key to freedom.

Freedom is not intellectual. After the intellect has understood that all the functions of the subtle body are not real, the status of the intellect as being 'mine' is also abandoned and one becomes the silent ground-witness of everything, like pure free, attributeless consciousness.

A birth (janma) is when the subtle body enthrals a gross body (sthūla sūkṣma śarīra saṁyogaḥ janmaḥ), based on karmic data. Death (maraṇam) is when the subtle body detaches itself from the gross body (sthūla sūkṣma śarīra viyogaḥ maraṇam) through the udāna prāṇa. In between, the subtle body temporarily withdraws unmanifested into the causal body (kāraṇa), and is absorbed into īśvara's knowledge body, which will lead to manifestation again when the time comes. This all happens via neutral laws, which can be deduced, but cannot be studied exactly.

Advaita vedānta states: Do not focus too much on your personal karma! Fascination with the details of my life and personality is an obstacle. What is advisable is that I do right actions, for example with regard to my lifestyle, in order to get appropriate results to let my subtle body ripen to emotional maturity, to understand my freedom. For that I must understand that every thought, every action leaves a trace. Cause and effect.

All movement, including mental movement is mithyā, depending on where, and in reality sadeva satya (satya, only (eva) existence, sat itself). The whole shadow play of saṁsāra will never come to an end, if I will nourish its truth. It is played out as an expression of the imperishable, infinitely peaceful self, which is never born, nor can die.

Sūkṣma śarīra is composed of:

1. Five organs of action (karmendriyaṇi), made of the five still pure rajas aspects of the five elements.

2. Five organs of knowledge (jñānendriyaṇi) or organs of sense, made of the five still pure sattva aspects of the five elements.

3. Five energies or life currents (prāṇāḥ), each made of the five combined aspects of rajas.

4. The fourfold internal instrument (antaḥkaraṇa), each function of which is made of the five combined aspects of sattva, the main functions of which are intellect (buddhi), memory (citta), mind, heart or emotional center (manas), and I-experience/ego (ahaṅkāra).

In all, nineteen tattvas (principles, concepts).

The subtle body is a body in the sense that it is a collection or combination of capacities or powers, which experience authenticity of worldly life (ignorance). The effect is that it seems as if the self (ātmā) has become identified (tādātmyam, 'that is I-ness'), and therefore wrongly limits itself.

Under the influence of the prāṇa (energy) udāna, the subtle body leaves the gross body, at the death (maraṇam or pralaya) of the physical body, to apparently continue in a new body. Death is thus the separation of the subtle and gross body. Because it concerns an identification with an appearance of itself, it is like a lucid dream for those who know it. It is all just appearance, nothing at all actually happens.

The self (ātmā), associated with the subtle body of a sage, knows that he or she is pure, single consciousness, and will not reincarnate further. This is because there is no desire to want anything in the world, nor the insight that there is anything to lose in the world.

Important here: In this way we 'program' God (īśvara) with our intentions and actions. God must give me results that reveal themselves in the subtle body. Consciously good intentions, in harmony with the good action that goes with it, qualify my thinking and feeling world for freedom.

This freedom goes so far that a wise person is just as little identified with his 'own' subtle body as with that of an 'other'. A wise person may think and say wise things, but may also make mistakes. No problem. She or he is free.

All in all we find that both ignorance and knowledge take place in the intellect of the subtle body. The wise person, like the self, is free from both ignorance and knowledge. The wise woman, the wise man is free from the wise woman or the wise man.

In other words: There is no reason for īśvara to give such a subtle body a result in the form of a new life. Why not? The wise person does not need anything from the world to reap the fruit that he or she is bliss. What is bliss? That he or she is completely free from the whole expedition, this is freedom from jīva and freedom from the notion of īśvara as being brahman who would actually have qualities.

So see the limiting power of neediness!

The following is not meant as hard science, but to distinguish between subtle and gross body. And to show that the mind is not in the brain, but is ‘connected’ to it, to cooperate with it.

In order to get a living experience through the subtle body, the subtle body cooperates with the gross body, which is part of the gross world. Take sound for example. Before consciousness activates sound, which is manufactured in a device that sends out a Bluetooth signal, which from a speaker or earphones via my ear, the brain, the subtle body, the causal body becomes a living experience, which appears to consciousness, a lot has ‘happened’.

An ear is nothing more than an organic receiver, and the brain part that belongs to it then acts as an amplifier or converter. That is why an ear can be replaced by a hearing aid, which replaces the organic hearing aid. Just like the lens of my reading glasses.

Feelings and thoughts are ‘in’ the subtle body. That only works if consciousness ‘shines’ on it, as it were. Consciousness remains free and unchangeable, but the upādhi is then ‘activated’, and it seems as if I am influenced by feelings or thoughts.

The subtle body is a module ‘between’ the gross body, the causal body and consciousness. It is all one big, objective machine. In principle, there is no difference between devices without a subtle body, such as nails, hair, stones and chip machines from ASML. It is all consciousness. Only living beings with a subtle body are actually self-conscious, and have self-reflection because the mind is a mirror that reflects consciousness with vṛttis in it (cidābhāsa, reflected consciousness, nothing more than pure cit, but then with the upādhis of thoughts and feelings, vṛttis, mental revolutions). Even if man thinks he has appropriated something and man distorts nature into culture, it is all one big īśvara machine.

As for the question of self-consciousness of AI. If a human being were able to plant a subtle body in a machine, the machine could become self-conscious. This is now called AGI (Artificial General Intelligence), although it is more about self-evolving than inherently self-aware. However, a human being will not be able to put a subtle body in a machine, since the subtle world and the world of meaning (!) belong to a different, more subtle order than the world of coarse (sthūla) bits, pulses, lasers, etc. This subtle world belongs to īśvara and in its entirety we call it hiraṇyagarbha.

The subtle body specifically penetrates the nervous system. That reaches all parts of the body, except nails and hair. The subtle body does not reach the latter two.

Because the subtle body, and therefore the feeling, stop at the boundaries of my body, I think that I stop there, and that I stand separately in the world as a body. This is a strong driver of ignorance.

The subtle body and its coarse instrument, the coarse nervous system, therefore merge in a human being. A bit comparable to the subtle body and its instrument, the coarse brain.

The absence of pain experience related to the gray matter of the brain (for example when it is cut) can be explained in this way. The brain is the main organ for connecting the subtle body to the rest of the body via the nervous system, and thus to the world. Through the brain, the feeling is 'reported' from the rest of the body (where the subtle body reaches), so to speak. The brain is not identical to the subtle body, but is directly permeated by it (vyāpti).

The other two bodies are the gross body (sthūla śarīram) and the causal body (kāraṇa śarīra). In the Vedānta, these three bodies are explained, in order to refute their status as independent realities (śarīra traya apavāda). Why? Because they are manifestations/appearances of consciousness, via its own apparent potency māyā.