The sixth chapter of the Chandogya is a father teaching a son who has come home from twelve years of study insufferably pleased with himself, and the father's opening move is to ask whether he learned the teaching by which the unheard becomes heard. He then runs a series of demonstrations: fruit cut open to a seed and the seed cut open to nothing; a tree cut and still living; salt dissolved into water. Each ends with the same refrain, that the subtle essence is the self of all this, and you are that. Shankara built Advaita on the sentence and reads it as a flat statement of identity. Ramanuja reads it as predication of a qualified whole. Madhva, remarkably, reads the Sanskrit as sa atmā tat tvam asi and gets you are not that — a reading almost nobody outside his school accepts, and a good illustration of how much of Indian theology is grammar under pressure.