Life and dating
Born in Kalady in present-day Kerala, Śaṅkara is said to have taken renunciation as a boy and travelled the length of the subcontinent in a short life — most accounts give him only thirty-two years. He held public debates with the leading philosophers of competing schools (Sāṁkhya, Mīmāṁsā, the Buddhists), and the historical record of those debates is the spine of the early Advaita commentarial tradition.
His core argument
Śaṅkara's reading of the Upaniṣads holds that only Brahman is ultimately real; that the world of plurality is māyā — not nothing, but not what it appears to be — and that the apparent jīva (individual soul) is in essence Ātman, which is not other than Brahman. The corollary is consequential: liberation (mokṣa) is not an attainment but a recognition of what was already the case. The bhāṣyas — his commentaries — work this argument out across thousands of pages of Sanskrit.
Legacy
Through the matha system and the centuries of commentarial tradition that followed, Śaṅkara's reading became the default frame for Hindu philosophical Advaita. The doctrine resurfaces almost intact in the twentieth century in the silent transmission of Ramana Maharshi and the dialogues of Nisargadatta Maharaj. The contemporary Western non-dual teachers — Spira, Mooji, Lucille — work in his lineage even when they do not name him.
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