Adi Shankara (pronounced ) (789 CE), also known as Ādi Śaṅkarācāri, Śaṅkara Bhagavatpādācārya and Ādi Śaṅkarācārya was an Indian philosopher from Kaladi in present day Eranakulam district, Kerala who consolidated the doctrine of advaita vedānta. His teachings are based on the unity of the ātman and brahman— non-dual brahman, in which brahman is viewed as nirguna brahman, brahman without attributes.
Shankara travelled across the Indian subcontinent to propagate his philosophy through discourses and debates with other thinkers. He is reputed to have founded four mathas ("monasteries"), which helped in the historical development, revival and spread of Advaita Vedanta of which he is known as the greatest revivalist. Adi Shankara is believed to be the organizer of the Dashanami monastic order and the founder of the Shanmata tradition of worship.
His works in Sanskrit concern themselves with establishing the doctrine of advaita (nondualism). He also established the importance of monastic life as sanctioned in the Upanishads and Brahma Sutra, in a time when the Mimamsa school established strict ritualism and ridiculed monasticism. Shankara represented his works as elaborating on ideas found in the Upanishads, and he wrote copious commentaries on the Vedic canon (Brahma Sutra, principal upanishads and Bhagavad Gita) in support of his thesis. The main opponent in his work is the Mimamsa school of thought, though he also offers arguments against the views of some other schools like Samkhya and certain schools of Buddhism.