Tat Tvam Asi - Thou Art That
The individual self is identical with the universal Self.
Tat Tvam Asi reveals that Atman (individual self) and Brahman (universal reality) are one. This mahavakya dissolves the illusion of separation between individual consciousness and cosmic consciousness.
That thou art.
This is one of the four great statements (mahavakyas) of the Upanishads.
Chandogya Upanishad
Written about in
- What the Upanishads say about loneliness
Uddalaka says "thou art that" to his son nine times in the Chandogya dialogue, with a fresh example each time. Repetition is the method — the tradition does not expect anyone to stop feeling separate after hearing it once.