Tat tvam asi

Bhagavan, is mayavi. The one with maya shakti.

How can the one with maya shakti, and a poor jiva be one.

Is it even possible.

It is possible if maya shakti is kalpita, or mithya, and if the reality is one and the same.

It is brahman with maya shakti that creates the multiplicity, while oneself remaining non dual and without name or form.

Maya exists with brahman as adhistAnam, so there is only brahman, is the mula shakti, the total shakti of brahman. Then with this shakti , brahman is reponsible for the 3 tasks of srshti, sthithi and laya.

The upadhi of human body mind, is a making of brahman using this shakti alone, a portion of this shakti is manifest as body mind, and the consciousness that inheres the body mind, is strictly all pervading non dual chaitanyam, brahman.

Tat tvam asi, is possible, only when looking from standpoint of truth consciousness as oneself, which is the reality of every person, and lends existence and consciousness to all that is here.

So to this body, this mind, which is kalpita, brahman lends existence, and brahman lends existence to the creator of this body and mind, to the manifester of all names and forms, and also to the unmanifest. 

Attribute is kalpita

The attributes of air, water etc. and the cause for all that, all of it is kalpita, or mithya in terms of reality. With this kalpanA shakti, brahman is ishvara. All that is here, is tat brahman, and tat brahman , is you, tvam asi. This is the teaching of advaita vedanta.

Advaita vedanta, makes it clear that there is an ishvara, and this jagat is an expression of this ishvara.

An Attribute doesnt limit the subtantive

Brahman or atman is the subtantive, and any name and form is an attribute to brahman. An attribute is not another vastu, rather it is the same vastu. But with attribute we all it in different name and form.
Same way truth brahman is one, we call it with different names and forms. 

Sakshi Chaitanyam, is brahman

Brahman is ishvara, or cause of the universe. Brahman by itself, am is simply atma.
Brahman is also ishvara only when looked from the standpoint of the upadhi, and not from ones own standpoint.

The standpoint is key here.

Ishvara is a point of view. From the point of view of maya shakti, brahman or atman is parameshvara.

Here the powers are all not dividing atma, into many, atma remains one, and with the power, appears as many beings, and as controller of all beings. 

Tat Tvam Asi

The vidya that shastra guru gives is tat tvam asi.

The person I, is equated to tat, ishvara.

It hence becomes the commitment of shAstra and guru to unfold how that could be possible.

Shastra and guru follow a methodology to unfold this knowledge.

Tvam is the self, the person, who is a born , lives , goes etc.
In deeper terms, he is the transmigrating jiva, who travels from one body to another, and has a sukshma sharira or subtle body.

In human form, he accumulates karma, due to kartrtvam, he is the doer, and for karma he gains bodies as karma phala.

This jiva is eternally appearing to be engaged in karma and karma phala experience, over and over again.

The jiva gains the desire to be free from this endless cycle of karma and karma phala, and gain fulfilment.

He sees it is not possible to be fulfilled via karma, the non fulfilment is not satisfied by some kind of karma, and some experience of temporal joys,  even if it continues to cyclically happen over and over again and again.

It is only via self knoweldge this jiva can be permanantly fulfilled.

That is because per shAstra, the jiva is himself limitless.

Now shastra has to unfold this.

Shastra says jiva is , in fact the sakshi chaitanyam, the witness consciousness who is the observer or witness of the 3 states of waking dreaming and sleeping, and the witness of gross subtle body, and causal body in the form of ignorance.

The jiva is told, that he is ishvara, which seems unebelievable, given ishvara has infinite wisdom, power, and all names and forms belong to ishvara.

This is unfolded, by making it clear, that the truth of the jiva is the witness consciousness, which happens to be sakshi chaitanyam. Sakshiness being a status assigned to the self shining consciousness, which of its own light happens to reveal objects.

Ishvara is the non different material and intelligent cause of the universe. The universe is present in unmanifest form and manifests, universe meaning ishvara with form.

So this unmanifest ishvara, manifests, in the manifest state, this same ishvara chaitanyam is indeed the sakshi chaitanyam.

But there is a difference in terms of the body, the total wisdom and names and forms, make the ishvara chaitanyam as parameshvara, while the individual ignorance, makes the ishvara chaitanyam to be taken to be jiva.

The ignorance results in the mistaken identity of oneself as the doer, and there being a doer, there would need to be an experiencer, and that lays the seed for varied experience as per karma of the one who considers himself as doer due to ignorance.

However when I see that I am ishvara chaitanyam, I am no more bound in terms of time or space, and in me there is no time or space.

The ishvara chaitanyam is in fact satyam , while the objects in the universe, or body of ishvara is in fact mithya, which has its reality in ishvara chaitanyam.

One can retain ones understanding of any name and form, and realise that the "is" when we say space is, time is, air is, water is etc. , is refers to sakshi chaitanyam, while space , air etc. refer to form with which ishvara appears. It can be seen to be ishvaras vibhuti.

Jiva identifying with self as ishvara chaitanya, is free from karma, and the individual body , mind that remains, is merged with total ishvara, and individual ego remains as a part of ishvara. 

Manifestation is mithya

We say brahman is manifest. Like a spider pulls out the thread or the web.

This entire jagat is experienced, it is manifest we say, it along with the experiencer are unmanifest during sleep, similarly in pralaya also all beings are unmanifest.

What is changeless in and through manifest and unmanifest is the reality of the experiencer which alone is the reality of experienced as well, which is I, the truth of I, when I say "experiencer".

In experiencer there is no thought, there is no experience of an experiencer, rather in every experience "I" am , "I" is the experiencer. Simply I.

This I is the truth of the experiencer. This I is also the truth of experienced.

Pure I, pure consciousness, is reality, wherein we negate the status of being experiencer, we also negate status of being experienced. We just retain the pure I, the pure self, brahman, which does not undergo any change whatsover.

This pure I, alone reflects in the mind as I thought, this pure I lights up every experience. The lighting up and the reflection, are both svarupa of I.

This pure I is the reality of prAna, the pure I is the reality of seeing, the pure I , is the reality of eyes, mind and so on. This pure I is the reality of maya shakti. Which means all that Is here, the experienced, is ishvara, and this ishvara, the visvarupa ishvara, is the will of ishvara.

Per the will of ishvara, this experience has manifest itself.

When I , see the will manifest, I know there is a person, a purusa, veda says there is a purusa, who is the nimitta upAdana kArana behind this experience.

The only possible way to know this bhagavan is through the mahavAkya, tat tvam asi.

Here the reality of this ishvara is none other than this I, the pure I. This pure I is indeed the truth of the ishvara we are referring to.

Its svarupa is svayamprakAshaka, atma jyothi, satchit , and I am able to appreciate , the presence of this bhagavat jagat rachana, wherein, I is experiencer, and this bhagavat jagat rachana, is in lieu of a orderly putting together of various elements and elementals, also it is mithya in terms of truth. Thereby, there is no other upAdana needed for this jagat other than this pure I.

For the supreme wisdom, there is no other upAdana, other than pure I, thereby pure I, is the truth of the supreme wisdom wielder. This is how I can say, the supreme wisdom wielder, is none other than I.
In I, there is neither supreme wisdom, nor limited wisdom, I , is free from names and forms, from maya shakti. Jiva individual is the form, truth of whom is this I.