Tat Tvam Asi -- That Thou Art
tat tvam asi
Tat tvam asi
Translation. That thou art.
Meaning
One of the four Mahavakyas (great sayings) of the Upanishads. Tat (That) refers to Brahman -- the infinite, unmanifest ground of all existence. Tvam (thou) refers to the deepest individual self -- the Atman, pure witnessing awareness. Asi (art) asserts their identity. The teaching is that the individual self and the universal Self are not two different things -- they are One.
Commentary
Found in the Chandogya Upanishad (6.8.7), this teaching appears in the dialogue between the sage Uddalaka Aruni and his son Shvetaketu. Shvetaketu had returned from twelve years of Vedic study, proud of his learning but without self-knowledge. The father guides him through a series of teachings about the subtle essence of all things and concludes each teaching with the refrain: "Tat tvam asi, Shvetaketu" -- "That thou art, Shvetaketu." The repetition is deliberate: the truth must penetrate through layers of identification until it lands as direct recognition, not merely intellectual understanding. Adi Shankaracharya took this Mahavakya as the foundation of Advaita Vedanta.
Reference: Chandogya Upanishad 6.8.7 · Tradition: Upanishad