"Thou art that" Shvetaketu.

Bhrigu Varuni went to his father Varuna saying, Sir, teach me Brahman.”

 Varuna said:

 “That from whence these beings are born, that by which, when born they live, that into which they enter at their death, try to know That. That is Brahman.” [Taittiriya Upanishad III-I]

   Uddalaka the preceptor, repeats ‘Tat Tvam Asi’ nine times to his disciple Svetaketu. This is repetition (Abhyasa). Brahman is doubtless unique, as He is Infinite and advitiyam, without a second. When you attain knowledge of Brahman everything else is known.

   “Thou art that”, Shvetaketu”; realize that ‘you are none else but that pure Self’, says Sage Aruni Uddalaka.

   This is the ultimate truth. It is for want of this realization that one wanders in this wilderness of mundane world of insatiable wants and takes repeated births to fulfil his desires and gets frustrated. This ‘Knowledge of the Self’ / ‘atma jnyan’ comes from self contemplation and no amount of intellectual exercise will help here. It is the ultimate of all Knowledge; it is not the knowledge of the material world (apara vidya). It is the spiritual knowledge (para-vidya), knowledge of the inner self. In ancient times, this supreme Knowledge was imparted to students by learned teachers called Acharyas since time immemorial. The method of teaching consisted of a strict ritualistic mode of learning where Veda was taught mostly by word of mouth (without any written scriptures) and learnt by- heart, memorized; what has been learnt and memorized came to be known as ‘smruti’ and that which is heard from the  Guru came to be known as ‘Shruti’. Each one of the Acharyas experienced the ‘Truth’ by personal effort- spiritual exercises or Sadhana and kept their individual experiences a secret, and later on imparted only to a few trusted students. There were many categories and levels of attainments and they communicated their teachings as ‘Upanishad doctrines’. Upanishad means imparted to disciple ‘sitting near’ the Acharya.

    Now, let’s see what the Upanishads say about the structure and the constitution of the Universe. In the Vedantic texts, we come across in different places different statements regarding the oriin of various forms and functions of things. Some texts say that the ether and air originated; some do not. Some other texts again make similar statements regarding the individual soul and the Pranas (vital airs). In some places the Sruti texts contradict one another regarding order of succession and the like.

     The following conversation between the Sage Yajnyavalkya and his wife Gargi regarding the Knowledge of the Self, the Brahman is very interesting. The Sage Yajnyavalkya said: That, O Gargi, the knowers of Brahman call the Imperishable, “It is neither gross nor subtle, neither short nor long, neither dry nor moist; It is neither shadow nor darkness, neither air nor akasa; It is unattached; It is without taste or smell, without eyes or ears, without tongue or mind; It is non-effulgent, without vital breath or mouth, without measure and without exterior or interior. It does not eat anything, nor is It eaten by anyone. Verily, under the mighty rule of this Imperishable, O Gargi, the sun and moon are held in their respective positions. Under the mighty rule of this Imperishable, O Gargi, heaven and earth are held in their respective positions. Under the mighty rule of this Imperishable, O Gargi, moments, muhurtas (about forty-eight minutes), days and nights, fortnights, months, seasons and years are held in their respective positions. Under the mighty rule of this Imperishable, O Gargi, some rivers flow eastward from the white mountains, others flowing westward continue in that direction and still others keep to their respective courses. Under the mighty rule of this Imperishable, O Gargi, men praise those who give the gods depend upon those who perform the sacrificial rituals and the Manes upon the Darvi offering. Whosoever in this world, O Gargi, without knowing this Imperishable, offers oblations, performs sacrifices and practices austerities, even for many thousands of years, finds all such acts but perishable. Whosoever, O Gargi, departs from this world without knowing this, Imperishable, is the miserable”

    But he, O Gargi, who departs from this world after knowing the ‘Imperishable’, is a knower of Brahman.  Verily, that Imperishable, O Gargi, is never seen but is the Seer; “it is never heard, but is the Hearer; it is never thought of, but is the Thinker; It is never known, but is the Knower. There is no other seer but ‘This’, there is no other hearer but ‘This’, there is no other thinker but ‘This’; there is no other knower but ‘This’.” By this Imperishable, O Gargi, is the unmanifest (avyakta) Space (akasha) pervaded (vishva-vyapi).”

  Then said Gargi, Venerable Brahmins, you may consider yourselves fortunate if you can get off from him through bowing to him. None of you, I believe, will defeat him in arguments about Brahman. Thereupon the daughter of Vachaknu held her peace. [Yajur Veda, Brih. Upa. III, VIII-Yajnavalkya and Gargi (II), 8- 12]