Adi Shankara (Sanskrit: आदि शङ्कर [aːdɪ ɕɐŋkɐɽɐ]) was an early 8th century Indian philosopher and theologian who consolidated the doctrine of Advaita Vedanta.[note 1] He is credited with unifying and establishing the main currents of thought in Hinduism. His works in Sanskrit discuss the unity of the ātman and Nirguna Brahman "brahman without attributes". He wrote copious commentaries on the Vedic canon (Brahma Sutras, Principal Upanishads and Bhagavad Gita) in support of his thesis. His works elaborate on ideas found in the Upanishads. Shankara's publications criticised the ritually-oriented Mīmāṃsā school of Hinduism. He also explained the key difference between Hinduism and Buddhism, stating that Hinduism asserts "Atman (Soul, Self) exists", while Buddhism asserts that there is "no Soul, no Self". Shankara travelled across the Indian subcontinent to propagate his philosophy through discourses and debates with other thinkers. He established the importance of monastic life as sanctioned in the Upanishads and Brahma Sutra, in a time when the Mīmāṃsā school established strict ritualism and ridiculed monasticism. 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 organiser of the Dashanami monastic order and unified the Shanmata tradition of worship. He is also known as Adi Shankaracharya, Shankara Bhagavatpada, sometimes spelled as Sankaracharya, (Ādi) Śaṅkarācārya, Śaṅkara Bhagavatpāda and Śaṅkara Bhagavatpādācārya.