Adi Shankara

Advaita means nondualism: Shankara argued that the true self, atman, is not ultimately separate from Brahman, the absolute reality. This became one of the major Vedanta traditions in India, especially through commentaries on the Upanishads, Bhagavad Gita, and Brahma Sutras.

He is commonly placed in the 8th century, although traditional chronologies and modern academic dating do not always agree. What is secure is his lasting role in systematizing Advaita Vedanta through Sanskrit commentary and debate.

Shankara taught Advaita Vedanta, where ultimate reality is nondual and liberation involves realizing the identity of atman and Brahman. Ramanuja, writing later, developed Vishishtadvaita, a qualified nondualism that preserves a stronger devotional distinction between God and individual souls.

The Upanishads are foundational Vedanta texts, and Shankara's commentaries gave them a rigorous nondual interpretation. His readings shaped later Hindu philosophy by treating liberation as knowledge of Brahman rather than only ritual action.