Śaṅkara (c. 788 to 820 CE). One of the most notable of Indian religious teachers, whose exposition of Vedānta is a great Indian classic. Converted in 800 CE to the monistic doctrine of Advaita Vedānta, he was an independent thinker and of a resolute character. He took a vow of celibacy. His commentary on the Brahma-Sūtra is entitled Naiṡkarmyasiddhi. Some Hindus, e.g., Rāmānuja, were so impressed by the seeming affinity of his thought with that of Buddhist philosophy that they charged him with being a sort of crypto-Buddhist.

Geddes MacGregor, Dictionary of Religion and Philosophy, New York: Paragon House, 1989