Upanishads declare ~ “Neti Neti—not this, not this, not that.” This does not mean that Brahman is a negative concept.+

Sag Sankara said: Just as the snake is superimposed on the rope, this world and this body are superimposed on Brahman or the Soul, the Self. If one gets knowledge of the rope, the illusion of the snake will vanish. Even so, if he gets knowledge of Brahman, the illusion of the body and the world will vanish.

The snake is only an idea: it disappears on inquiry but deeper Self-search reveals the fact that the rope is also an idea and its reality will be exposed when wisdom dawns. There is neither snake nor the rope in reality because from the ultimate standpoint the duality is merely an illusion created out of the Soul, the Self. 

The Soul is the Self. The Soul is present in the form of consciousness.  Consciousness is the root element of the universe. From consciousness, the universe comes into existence. In consciousness, the universe resides. And into consciousness, the universe is dissolved.  Consciousness is the parent of all that is there is.  Consciousness is the only reality, and the universe too but an illusory manifestation. 

Consciousness is within, consciousness is without; consciousness is before, consciousness is behind;  consciousness is on the right,  consciousness is on the left;  consciousness is above and consciousness is below. Consciousness is not an object, as it is invisible, beyond the reach of the physical eyes.  Consciousness is the ultimate truth. And the ultimate truth is Brahman or God in truth.

The world in which we exist is merely an illusion created out of consciousness.  Therefore, hold on to consciousness which is real and eternal, and mentally negate the world in which we exist by realizing the world in which we exist is nothing but consciousness.  

Upanishads declare ~ “Neti Neti—not this, not this, not that.” This does not mean that Brahman is a negative concept, or a metaphysical abstraction, or a nonentity, or a void. It is not another. It is all-full, infinite, changeless, “Self’-existent, “Self’-delight, “Self’-knowledge, and “Self’-bliss. It is the essence. It is the essence of the knower and the known.

Sage Sankara said: - The Brahman is impersonal, without Gunas or attributes (Nirguna), formless (Nirakara), (without special characteristics (Nirvisesha), immutable, eternal and non-agent (Akarta). It is above all needs and desires. It is always the Witnessing Subject. It can never become an object as it is beyond the reach of the senses. Brahman is non-dual, one without a second. It has no other beside it. It is destitute of difference, either external or internal. Brahman cannot be described because the description implies the distinction. Brahman cannot be distinguished from any other than it. In Brahman, there is not a distinction between substance and attribute.

Remember:~

In Manduka Upanishad Brahman and Atman are defined as the same:~

सर्वं ह्येतद् ब्रह्मायमात्मा ब्रह्म सोयमात्मा चतुष्पात् / sarvam hyetad brahmaayamaatmaa brahm soyamaatmaa chatushpaat –

Manduka Upanishad, verse-2

Translation:

sarvam(सर्वम्)- Whole/All/Everything; hi(हि)- Really/Just/Surely/Indeed;etad(एतद्)- This here/This; brahm(ब्रह्म)- Brahm/Brahman;ayam(अयम्)- This/Here; aatmaa(आत्मा)- Atma/Atman; sah(सः)- He;ayam(अयम्)- This/Here; chatus(चतुस्)- Four/Quadruple; paat(पात्)- Step/Foot/Quarter

Fragmented Verse:

सर्वम् हि एतद् ब्रह्म अयम् आत्मा ब्रह्म सः अयम् आत्मा चतुस पात् / sarvam hi etad brahm ayama aatmaa brahm sah ayam aatmaa chatus paat

Simple Meaning:~

All indeed is this Brahman; This Atman is Brahman; He, this Atman has four steps/quarters.

While Brahman lies behind the sum total of the objective universe, some human minds boggle at any attempt to explain it with only the tools provided by reason. Brahman is beyond the senses, beyond the mind, beyond intelligence, beyond imagination. Indeed, the highest idea is that Brahman is beyond both existence and non-existence, transcending and including time, causation, and space, and thus can never be known in the same material sense as one traditionally 'understands' a given concept or object.

Imagine a person who is blind from birth and has not seen anything. Is it possible for us to explain to him the meaning of the color red? Is any amount of thinking or reasoning on his part ever going to make him understand the sensation of the color red? In a similar fashion, the idea of Brahman cannot be explained or understood through material reasoning or any form of human communication. Brahman is like the color red; those who can sense it cannot explain or argue with those who have never sensed it.

Bhagavad Gita:~  brahmano hi pratisthaham ~ Brahman is considered the all-pervading consciousness which is the basis of all the animate and inanimate entities and material. (14.27)

In Advaita Vedanta: - Brahman is without attributes and strictly impersonal. It can be best described as infinite Being, infinite Consciousness, and infinite Bliss. It is pure knowledge itself, similar to a source of infinite radiance. Since the Advaitins regard Brahman to be the Ultimate Truth, so in comparison to Brahman, every other thing, including the material world, its distinctness, the individuality of the living creatures, and even Ishvara (the Supreme Lord) itself are all untrue. Brahman is the effulgent cause of everything that exists and can possibly exist. Since it is beyond human comprehension, it is without any attributes, for assigning attributes to it would be distorting the true nature of Brahman. Advaitins believe in the existence of both Saguna Brahman and Nirguna Brahman; however, they consider Nirguna Brahman to be the absolute supreme truth. 

Chandogya Upanishad: - One who meditates upon and realizes the “Self’ discovers that everything in the cosmos-- energy and space, fire and water, name and form, birth and death, mind and will, word and deed, mantrams and meditation--all come from the “Self’.

So, it clearly says the one who meditates upon the “Self’ (consciousness) discovers that everything in the cosmos-- energy and space, fire and water, name and form, birth and death, mind and will, word and deed, mantrams and meditation--all come from the “Self’. Therefore, there is a need to know the fact that, the true “Self’ is not physical but the Soul in order to realize the fact that:  the cosmos-- energy and space, fire and water, name and form, birth and death, mind and will, word and deed, mantrams and meditation--all come from the “Self’, which is in the form of consciousness. 

Atman is Brahman. Brahman the Absolute is alone real; this waking is unreal, and the three states are non-different from Brahman. 

Remember:~

Sage Sankara: ~ “VC~ All this universe which through ignorance appears as of diverse forms, is nothing else but Brahman which is absolutely free from all the limitations of human thought.

Sage Sankara: ~VC~ If the universe is true, let it then be perceived in the state of deep sleep also. As it is not at all perceived, it must be unreal and false like dreams.

The universe hides the Soul, the Self. If you realize the nature of the universe then you will know the truth hidden by the universe.

That is why Sage Sankara says: ~ V.63 ~ "Without knowing and examining the external world, one can’t know Truth, as the idea that the external world exists, won't go. It can go only by an inquiry into the nature of the external world.

In deep sleep there is nothing to observe when there is only the observer left, then the observer itself becomes the observed -- because there is nothing else to observe. Deep sleep is still a state of ignorance because we become aware of the deep sleep experience only in waking experience, which is the state of ignorance.

Only through Self-knowledge or Brahma Gnana or Atma Gnana Self-awareness is possible.

In Self-awareness, the witness simply witnesses itself.

The Seer sees itself. There are no thoughts, no objects. The Soul becomes still; it simply becomes a light unto itself. There is nothing that it lights, it lights only itself, the Soul, the Self is surrounded by silence, surrounded by Stillness. It is the objectless awareness in the midst of objects.

The Soul becomes the Soul in Self-awareness. Self-awareness itself is enlightenment. The Soul consciously remains aware of itself in the midst of the dualistic illusion (form, time, and space).

The ‘I’ has dissolved as the Soul, the Self, which is present in the form of consciousness.

The ‘I’ has dissolved means the mind has dissolved as the Soul.

The mind has dissolved means the form, time and space have dissolved as the Soul.

The form, time, and space dissolved as the Soul-  means the universe has dissolved as the Soul.

The universe has dissolved means the waking has dissolved as the Soul.

The waking has dissolved as the Soul means the individual experience of the birth, life, death, and the world has dissolved as the Soul.

The individual experience of birth, life, death, and the world has dissolved as the Soul means the dualistic illusion is dissolved as the Soul.

The Soul alone exists as the formless, timeless, and spaceless eternal existence.

The seeker must first know the Soul is the only reality and that the world in which he exists is an illusion. The seeker must reason upon this truth from all points of view and up all further argumentation and realize the truth. 

This realization comes from being certain that Soul is the ultimate truth or Brahman or is real and the world in which he exists is merely an illusion created out of consciousness. : ~ Santthosh Kumaar