Aham eva idam sarvosmi!
"I" is all this mental phenomenal world. "I" is Universal Subject (in the sense of consciousness/awareness) and Mental phenomenal world is the Universal Object (consisting of cognitions, re-cognitions, and communications).
Both are made up of same chit energy (psychic energy) and are one and the same.
Atman/Brahman is pure - object-less - consciousness; The Seer.
Idam is object-filled awareness; The Seen.
During cognition/communication, distinction/discern/discrimination /differentiation between the Seer and the Seen, is apparent/virtual/unreal.
In reality, the Seer and the Seen appear together and disappear together. That means the awareness and mental phenomenal world rise and set together. When mental phenomenal world is not being cognized, re-cognized or communicated, pure consciousness is revealed, which hitherto is in the background is like "sruthi" behind during musical concert or like paper on which matter is written or cine-screen on which virtual images appear as cinema.
During and after, sruthi, paper and cine-screen are present simultaneous to music, matter and cinema. They present themselves in their real and natural form when the super-impositions on them, the music, matter and cinema cease to be.
Similarly, pure consciousness or unoccupied awareness or content-free contentment or object-less subject or mental phenomenon - free calm mind the original state and form of mind, the Self/Atman/Brahman is experienced as Peace, Bliss, Silence, the original identity of "I", when the virtual/unreal super-imposition, the mental phenomenal world - jagat/ excuses itself from the consciousness/ awareness.
This state is the advaita / state of mind.
When mental phenomenal world / / jagat is perceived, the state is dvaita / state of mind.
Mind oscillates between these states and simultaneously uses these to draw information to cognize, (through sense organs), 're-cognize (through inner mental tools - manas, buddhi, ahamkaaram, chittam and communicate through action organs.
This is the essence of formation and construction of human cognition / 're-cognition / communication as available in the Upanishads / Atma-, Brahma- jnaana and the shaddarshanas - nyaaya, vaiseshika, saamkhya, yoga, poorva and Uttara meemaamSaas. Uttara meemaamsa is also known as Vedanta.
The same information in Brahmajnaana is used by Indian grammarians to propose theory of language acquisition and communication proposing and cultivating Sabdabrahma Siddhanta.
Upanishadic insight is not merely out-worldly but is scientific containing information to use in the modeling of human cognition/language acquisition/communication.
Let us use our ancient wisdom in sciences too in addition to spirituality and religion. Let us know our knowledge potential.