This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
The Upanishads are not a single, systematic text. They are a collection of philosophical dialogues and speculations, composed by different hands over centuries, and they say different, sometimes conflicting things about the relationship between Brahman, the ultimate reality, and the individual self. Shankara's achievement, working in the eighth century CE, was not to invent a new doctrine so much as to read the whole collection through one governing claim, tat tvam asi, that thou art, the Upanishadic formula he took as declaring the individual self, atman, strictly identical with Brahman rather than merely related to or derived from it. Everything else in his system follows from taking that identity literally. If atman and Brahman are truly one, then the ordinary experience of being a separate self, distinct from other selves and from the world, has to be explained away rather than simply accepted, and Shankara's explanation is maya, a term usually translated as illusion but closer in his own usage to superimposition, the mistaken layering of multiplicity and difference onto a reality that is actually undivided, the way a coiled rope glimpsed in dim light is mistaken for a snake. The world of ordinary experience is not, on this reading, simply unreal in the way a dream is unreal; it has a provisional, lower-order reality, real enough to act in and suffer in, but not real in the way Brahman alone is real. Liberation, moksha, is therefore not something achieved by ritual or effort in the ordinary sense, since there is no actual separate self to be liberated, it is achieved by a kind of knowledge, recognizing what was already true, that the self one takes oneself to be was never really separate from Brahman at all. This is why Shankara insisted commentary, careful argued interpretation of the triple canon, was itself the philosophical method: the truth was already stated in the texts, and philosophy's job was to read it correctly rather than to discover it independently.