The Chāndogya Upaniṣad opens with one of the most vivid meditations on Oṃ in the entire tradition (ChāU 1.1): Oṃ is the Udgītha (the high chanting note of the Sāma Veda), Oṃ is the Brahman that is nearest, Oṃ is the best of all essences. The text then embarks on a journey through a remarkable range of speculative topics — before arriving, in Book 6, at what is arguably the most famous philosophical teaching in all Indian literature.
Tat Tvam Asi — "That thou art" (ChāU 6.8.7)
The salt in water — the invisible essence (ChāU 6.13)
The Udgītha meditation — ChāU 1.1–4
The Chāndogya opens with an extended philosophical meditation on the Udgītha (the chanted syllable of the Sāma Veda, which is Oṃ). Uddālaka Āruṇi's teaching in ChāU 1.1 establishes the identity of the Udgītha, the Sāma, and Brahman through a series of equivalences — not allegory but ontological identification. The philosophical method here is the upāsanā (meditative identification): by meditating on the Udgītha as Brahman, the meditator progressively realises the identity. This is the Chāndogya's contribution to the Vedic-to-Upaniṣadic transition: the external ritual element (chanting) becomes a vehicle for internal philosophical recognition. Source: Olivelle (1996), ChāU 1.1–4.
Nārada and Sanatkumāra — knowledge and Bhūman
ChāU 7 contains one of the most sophisticated pedagogical dialogues in the Upaniṣads: the sage Nārada — who has mastered all the existing sciences (the four Vedas, history, grammar, mathematics, military science, and much more) — approaches Sanatkumāra confessing that despite all this learning, he is grieving. He does not know the Self. Sanatkumāra's teaching progressively guides Nārada from ordinary knowledge to the highest — the Bhūman (the infinite, the full) — which Sanatkumāra identifies with happiness, immortality, Brahman. The dialogue is a paradigm for the difference between information and wisdom. Source: Olivelle (1996), ChāU 7.
ChāU 1.1–4; 5.3–10; 6.1–16; 7.1–25 (Olivelle, OUP, 1996). Gambhirananda (trans.), Chāndogyopaniṣad (Advaita Ashrama, 2010).
Rāmānuja's counter-reading of Tat Tvam Asi
The Chāndogya's Tat Tvam Asi is the single most debated verse in the entire Vedāntic tradition — because its interpretation determines whether one's Vedānta is Advaitic (non-dual) or Viśiṣṭādvaitic (qualified non-dual). Śaṅkara reads it as a statement of absolute identity: the individual Ātman (Tvam — You) IS the absolute Brahman (Tat — That), without any qualification. The apparent difference between individual and absolute is a product of Avidyā (ignorance) superimposed on the one undivided Brahman.
Rāmānuja rejects this reading. He argues that the word tat (That) refers to Brahman with qualities (Viṣṇu, the personal God), and that the identity being taught is not absolute undifferentiated identity but the identity of the individual self as constituting the body of God. The individual self (Tvam) is real, not illusory, and it IS in some sense That (Tat) — because everything that exists is the body of Viṣṇu. But this does not mean the individual dissolves into an undifferentiated absolute; it means the individual is permanently part of God's body in a relationship of qualified, not absolute, identity. Source: Carman (1974), Ch.8; Thibaut (SBE Vol.48, 1904).