Śaṅkara, an Indian philosopher born and probably active in the eighth century CE, was a renowned scholar with whom non-dualism (Advaita) in Hindu thought is associated.
According to non-dualists, there is just one thing, sometimes called brahman or ātman. In Śaṅkara’s case, there is only one ultimate reality called brahman.
Brahman has no temporal properties, spatial properties, and internal complexity or division. It is “one only, without a second”. Ultimate reality and the self are identical, and Śaṅkara wanted to explain why people did not realize this and fell for the illusion (māyā) that the self exists separate from brahman. Māyā refers to that which appears real based on experience but which does not have ultimate existence. Śaṅkara considered the phenomenal world of experience māyā.
Śaṅkara’s uses the analogy of clay to illustrate the difference between objects and brahman. A lump of clay can be shaped into new forms, such as into a plate or pot, and the clay itself continues through each transformation. The clay is, therefore, more real than the objects into which it can be shaped and has continuity, unlike the objects. The clay, according to Śaṅkara’s analogy, is analogous to brahman, the underlying existence of the universe, and the pot is analogous to objects. The reader notices the centrality of brahman in Śaṅkara’s analogy. The pot does not exist apart from the clay. The pot depends on the clay for its being, it emerges out of the clay, is sustained by it, and resolves back into it upon its destruction.
Śaṅkara’s maintained that people misunderstood the self by equating it with the body, sense organs, or the mind. He uses the example of the traveler who mistook a rope for a snake. The traveler superimposed a false impression (a snake) upon the truth (the rope). Similarly, Śaṅkara maintained that false ideas are imposed on the self (ātman) and failed to recognize that the ātman is brahman. Only by removing ignorance or stop denying the equation between ātman and brahman could liberation or release (mokṣa) be achieved from the cycle of rebirth and redeath (Saṃsāra). Śaṅkara bases his argument on Vedic passages and declares “These sruti passages indeed reveal that samsara results from the understanding that Atman is different from Brahman”. One needs to realize the self’s identity with brahman.
Śaṅkara’s non-dualism was introduced to the West by the traveling teacher Vivekananda (1863-1902). In Vivekananda, Westerners encountered a modern interpretation of Śaṅkara’s ideas about Vedanta and learned that the impersonal, ultimate reality was also the personal God that people worshipped. This God was also the higher self within each human being.
Knott, Kim. 2000. Hinduism: A Very Short Introduction. Oxford: Oxford University Press