Consolidated by Ādi Shankaracharya (8th century CE), Advaita proposes that Brahman is the only reality, and the phenomenal world is an illusion (māyā). It teaches that individual consciousness (ātman) and universal consciousness (Brahman) are identical, famously expressed as 'Tat Tvam Asi' (That Thou Art).
Founded by Makkhali Gosala (6th century BCE), Ājīvika taught a doctrine of complete determinism and fatalism (niyati). It denied free will and karma, asserting that all beings progress through a predetermined cycle of 8.4 million rebirths before automatically attaining liberation.
Propounded by thinkers like Bhaskara (9th-10th century CE) and Nimbarka (13th century CE), this Vedantic school holds that the relationship between Brahman and the world/souls is one of simultaneous difference and non-difference, like the relationship between waves and the ocean.
Founded by Gautama Buddha (6th-5th century BCE), Buddhism rejects the authority of the Vedas and proposes the Four Noble Truths and the Eightfold Path. It denies the existence of an unchanging self (anātman) and emphasizes dependent origination (pratītyasamutpāda) and the impermanence of all phenomena.
Attributed to Brihaspati (6th century BCE), Cārvāka was a materialist and skeptical school that rejected supernatural elements, afterlife, karma, and religious rituals. It accepted only direct perception (pratyakṣa) as a valid means of knowledge and advocated hedonism as the purpose of life.
Established by Madhvacharya (13th century CE), Dvaita Vedānta asserts five fundamental and eternal distinctions: between God and individual souls, between God and matter, between individual souls and matter, between one soul and another, and between one material entity and another.