In atitaverante, there is only one consciousness in which these are appearnces. There is nothing outside that. So the meaning, final meaning of that thou art, is established by jahd ajahad lakhana. Its an implied meaning. This is called luxiart. What is the luxiart of tam? Pure consciousness. Luxiarta of tates pure consciousness. As that tat tomasy, that thou art is established e equation works. Whichever way you go, what will you come to? You will come too.
Sage Uddalaka asks his son Svetaketu: What is that knowledge by which we hear the unhearable, perceive what cannot be perceived and know what cannot be known? Inspired from this story from the Chandogya Upanishad, Swami Sarvapriyananda teaches the great saying (mahavakya) - Tat Tvam Asi (That Thou Art).
This discourse is also inspired from a verse from the Brihadharanyaka Upanishad (Mantra 4.4.12) as taught in the book, Pancadasi by Vidyaranya: "If a man knows the Self as ‘I am this,’ then desiring what and for whose sake will he suffer in the wake of the body?"
Mantra 4.4.12:
आत्मानं चेद्विजानीयादयमस्मीति पूरुषः ।
किमिच्छन्कस्य कामाय शरीरमनुसंज्वरेत् ॥ १२