Atma is self evident

Atma is always self evident.

I am is atma.

Atma is self evident, but does not have any attributes, nor is an object of experience.
It is the subject I.

In atma there is no parts, there is no bheda , there is no attributes, there is no division.

Atma is partless whole.

Atma is not available as an object of experience.

Atma is not time wise limited or space wise limited like worldly objects.

The body and mind are objects, atma is the subject.

Atma does not have any of the features of body mind.

This is brahman, not limited, partless and self evident.

Atma is consciousness, it is chit, it is awareness, referring to I, referring to its difference w.r.t all known objects that are inert.

How do we explain then status of brahman w.r.t the experience of body mind?

What is this jagad, etc.?

All that is handled by shAstra as well.

The brahman is presented as the cause, with a shakti or power called maya shakti.

Maya shakti is power to manifest and unmanifest names and forms. Brahman is hence the non different cause both intelligent and material cause.

Hence the object world resolves in brahman the cause.

The subject I, is the subject w.r.t object and by itself is free from being both subject or object.

One is paramartha, another is lower order of reality , mithya, not as true as satyam.

Mithya is negatable, since when Mithya is Satyam IS. When satyam IS, there is nothing else.

Where pot is clay is. Where clay IS, there needs to be nothing but clay.

With clay buddhi all is clay.

with pot buddhi, pot is, and clay buddhi is by default.

The cause

Everything must have a cause, and causation hunting for an 'attributeful' cause leads to an infinite regress.

Causation hunting for a single cause leads us down the atomic route, where again its a play of dimensions and infinite regress.

Even if we look at trigunAtmika mAya, as the cause, and look at the sankya definition, that pradhana which is matter independent of chaitanyam is the cause, that is also not acceptable. Reasons being manifold, as highlighted in upanisad.

What is not available in the means of knowledge has to come from veda, so first of all that matter is independent and it is a cause is not the vedik purport.

Secondly it is even not acceptable to general logic. Since if matter were the cause, then how does subtle matter show consciousness of some form or other? So just matter independently existing cannot be a cause. It cannot have its own existence, even if we say both exist independently, then two say both we need to cognize two things. Anything that is cognized can be counted.  If we count two causes, one is me consciousness and other is anatma, then is anatma satyam or mithya?

If anatma exist independently we have to agree to a definition for independent existence. Now that which is self revealing alone can be self existent. We see that anything in nature in object world is not self existent. Also not self revealing, or self evident, it needs consciousness to reveal it.

To see this exist, consciousness is needed. But even then if we argue that it has its own existence and its just revealed, even then we need to understand that any revealed object is essentially knowledge.

Why? When we look at a tree, isn't it knowledge?
A tree entails knowledge, when tree is revealed to the eyes, some knowledge is also revealed about the tree.Can knowledge exist independently? What is knowledge? Knowledge entails there has to be a knowledgeable being. Can knowledge exist independent of a knowledgable being?

It is against ones general understanding. It is not in general understanding, neither does shruti say so.
Hence is it is not possible.

Now if the matter is indeed knowledge of a knowledgable being, then how about existence of that matter, is its existence independent, obviously not.

Reason being lets look at existence, B cannot exist without A, means B has no existence of its own.
For example the snake cannot exist without rope, which means snakes existence or being is on the rope alone.

We need to understand existence clearly, existence or sat has no gunas and neither is it an object . Existence is the subject, not subject to objectification.

Now the object world takes existence from sat, and has the duality of knower, known , knowledge.

This is the knowledgeable being, who is in the form of knower, known and knowledge all 3.
Brahman itself is pure chit, not subject to being knower, known or knowledge. So brahman that is limitless has to be all 3, all 3 being mithya, there is no other brahman.

Atma Viveka

Upanisad communicates the reality that is brahman, by separating out the maya component and leaving just the essence that is the truth.

This is done by looking at the truth from various angles.

Individual

The individual is looked at in various ways. Here individual refers to the person who says 'I', this person is what we call atma, or self.

This self is commonly identified as
a. Body Mind All the qualities of the body mind are taken to be as good as the self. Therefore the person is forever complex ridden, and looking to improve the body mind, and how he 'feels' about himself or herself.
b. Doer and Enjoyer The self is said to be a doer and enjoyer. Hence the person is attached to karma, and the results of karma.
c. Waker, Dreamer, Sleeper The person identifies himself with the waker dreamer and sleeper. He thinks he is a person with a body mind, who is waking, dreaming and sleeping.

Separating atma from anatma
In order to understand what atma or how atma or self really is some methodologies are adopted.

a. Sharira trayAtitaH

The one who is other than the 3 bodies. 3 bodies includes gross body, subtle body which is mind and the subtle organs of hearing and so on.
Atma is understood as the sAkshi or witness to the 3 bodies. I witness my body changing from young to old, I witness hunger and thirst, I witness my thoughts and so on.

b. AvasthA traya sAkshi

I am witness to the 3 states of waking , dreaming and sleeping.

Here atma is again understood to be a witness, and not the dreamer or waker or sleeper itself.

Witness is what we call as 'chit'

This witness is called as chit, or consciosness. Hence the very same, very well known atma, who I used to think I am as good as this body, vedanta questions this conclusion, and clarifies, that I am not as good as the body, but I am the consciousness principle.

Nature of chit

Vedanta talks a little more about the nature of chit.
a. Chit is self evident, nothing else is needed to make chit evident, it is that in whos presence anything that can ever become evident , becomes evident, but chit itself is that self evident entity
b. Being self evident chit is self existent
c. Chit has no attributes. It is nirgunaH
d. Chit is not limited by space, in fact space is evident to oneself
e. Chit is not limited by time
f.. Any sentient or conscious being reflects chit
g. Chit is the illuminator w.r.t any object that becomes evident, or reflects chit, such as mind reflects chit, and appears to be the 'knower', while objects become evident to chit. However chit itself is like the sun. In presence of suns light things are revealed, however light itself doesnt perform any action to illumine, simply in its presence things are revealed

Ishvara

Second angle in which we look at brahman is as ishvara.
Ishvara is the causal being for this jagad.

Jagad includes all that is here, includes my own body mind also.

Ishvara is the non dual cause.

How? How means, vedanta is the pramAna for this.

Vedanta reveals what is not known to our sense organs and other inferential means of knowledge. It is a revealing instrument, a means of knowledge.

Vedanta says, that this ishvara is a causal being. She is the non dual causal being, with creative potential or power, otherwise known as shakti.
Shakti can be looked at as 'isccha shakti', 'kriya shakti' and 'gnana shakti', the power to desire, to create and to know.
She is also looked at as the one who wields 3 gunas, sattva rajas and tamas.

The upanisad says that this causal being desired and from her arose the different worlds. From her arose the 5 basic elements , which evolved into the numerous lokas and its beings.

Now the question really is what is the nature of this being.

Is she inert , or conscious, or is she a combination of inert and conscious being?

What is her essential nature.

The veda says ishvara is

If her nature is inert, that is not possible since to know the inert being, another conscious being is needed.

Then is ishvara a combination of inert and conscious?

It is, but this combination has to be understood, since there are various types of combinations.

There is a combination where two entities are mixed. This means matter and consciousness are two entities and mix to form ishvara.

Again this is not possible, since if matter were to exist independently, it will not be only revealed to exist in presence of consciousness.

Also even if we assume it to exist, then ishvara becomes limited,then which one is ishvara? is ishvara matter or is it conciousness.

Brahma sutras in detail quash this logic that matter and consciousness are separate entities.

Hence the only valid combination is that of satyam mithya.

This means consciousness is satyam and matter is mithya.

Like a clay pot. Clay is satyam and pot is mithya.

Same way ishvaras 3 gunas of sattva rajas and tamas are her maya component, qualifying to be called as mithya, while her essential nature is consciouness which is satyam.

Therefore ishvara is called as satyam. The cause. Tat.

Tat Tvam Asi

The ishvara and jiva are equated. How can they be equal. They cannot be equal if we look at their attributes. One is limited attributes of body mind, other is limitlessly endlessly splendourous attribute of entire universe including the body mind.
However if you look at the essential being, it is none other than consciousness or chit, which is the cause satyam. Sat.

Chit and Sat are one and the same. This is the one being, the one atma.

That atma alone is I. I alone is atma or brahman which with gunas appears to be two , ishvara and jiva.