Tat Tvam Asi

It is among the four statements the Advaita tradition designates mahavakyas, great sayings, and it may be the most consequential three words in Indian philosophy. It is also translated in two incompatible ways.

The setting is the sixth chapter of the Chandogya Upanishad. Uddalaka Aruni is instructing his son Shvetaketu, who has returned from twelve years of Vedic study rather pleased with himself. The father takes him through a series of demonstrations, clay and clay pots, salt dissolved in water, a banyan seed, each ending with the refrain, and the refrain is repeated nine times.

The traditional reading, and Shankara's, takes tat as the ultimate reality and tvam as the individual, and reads an identity: that you are. On this reading it is the compressed statement of non-duality, and the whole of Advaita Vedanta is an unfolding of it. Ramanuja read the same words within a qualified non-dualism, and Madhva performed a word division that produces the opposite sense, that you are not, which is grammatically possible in Sanskrit and is not a joke.

A separate modern proposal, from Joel Brereton, reads tat not as an ultimate but as referring back to the specific example just given, so the refrain would mean something closer to "that is how you are", the point being pedagogic rather than metaphysical. That reading is argued from the structure of the chapter and is taken seriously by Sanskritists without having displaced the traditional one.

Three words, four readings, and the schools of Vedanta divide along them.

The designation itself has a history that the phrase's fame obscures.

The scheme of exactly four great sayings, one drawn from each of the four Vedas, is not in the Upanishads. It is a later doxographic arrangement, systematised within Advaita and used pedagogically, in which this statement from the Chandogya is paired with three others, aham brahmasmi from the Brihadaranyaka, prajnanam brahma from the Aitareya, and ayam atma brahma from the Mandukya. The neatness of one per Veda is the giveaway: it is a teaching device.

Later Advaita developed a further scheme distinguishing the four by grammatical person and function, treating one as instruction from a teacher, one as the pupil's realisation, and so on. This is genuine tradition and it is not Upanishadic.

What the Upanishad itself is doing in that chapter is closer to natural philosophy than to mysticism. The demonstrations are about what things are made of and whether a subtle cause can persist unperceived in its effect, the salt is invisible in the water and is present throughout it. The famous line arrives as the conclusion of a physical argument.

Modern usage tends to lift the three words entirely clear of the chapter and present them as a standalone assertion of the unity of the self and the absolute. That is a defensible tradition with over a thousand years behind it. It is not what a reader encounters on opening the text, and the difference is worth knowing about before deciding which one is being quoted.