Yājñavalkya is the most prominent named teacher of the Bṛhadāraṇyaka Upaniṣad, where he is depicted debating rival Brahmins at King Janaka's court and instructing his wife Maitreyī on the nature of the self before renouncing household life. Tradition credits him with the formula "neti neti" ("not this, not this") for characterizing the ultimate self as irreducible to any finite predicate, with an early articulation of ātman-brahman identity, and with the claim that liberating knowledge of the self, rather than ritual sacrifice alone, is the highest good.
Intellectual setting
Yājñavalkya belongs to the late Vedic period associated with the Bṛhadāraṇyaka Upaniṣad and the Śatapatha Brāhmaṇa, when philosophical speculation about ritual, sacrifice, and the self was developing out of the earlier Brāhmaṇa literature in the Videha region of what is now northern India and southern Nepal. The texts associated with him record a shift from sacrificial ritualism toward interior, knowledge-based paths to liberation.
Key ideas
Neti neti: the indescribable self
Yājñavalkya taught that the innermost self (ātman) cannot be captured by any positive description - "not this, not this" - because it is the subject of all knowing and so can never itself become an object grasped the way external things are grasped.
The self as dearer than all else (the dialogue with Maitreyī)
In his dialogue with his wife Maitreyī before renouncing household life, Yājñavalkya argues that husband, wife, wealth, and children are each loved not for their own sake but for the sake of the self, and that knowledge of the self, not a share of material inheritance, is what she should therefore seek.
Legacy
Passages attributed to Yājñavalkya in the Bṛhadāraṇyaka Upaniṣad became foundational texts for later Vedānta, cited repeatedly by Śaṅkara, Rāmānuja, and other commentators on the Brahma Sūtras, and his teaching on ātman-brahman identity and the "neti neti" method remain central reference points in classical and modern Hindu philosophy.