Adi Shankara (788–820 CE) was an Indian philosopher and theologian who consolidated the school of Hindu philosophy and religious practice known as ‘Advaita Vedanta’ (literally, “not-two”). The term Advaita refers to the idea that the soul (true Self, Atman) is the same as the highest metaphysical Reality (Brahman). Followers seek spiritual liberation through acquiring knowledge (vidyā) of one’s true identity as Atman, and the identity of Atman and Brahman. Advaita Vedanta emphasizes ‘Jivanmukti’, the idea that moksha (freedom, liberation) is achievable in this life, in contrast to Indian philosophies that emphasize videhamukti, or moksha after death. Many scholars describe Advaita Vedanta as non-dualistic, or a form of monism.
Shankara’s works elaborate on ideas found in the earliest Upanishads (the most widely known part of the Vedas, which are the literary spiritual core of Hinduism). Credited with unifying and establishing the main currents of thought in Hinduism, his works in Sanskrit discuss the unity of the ‘Atman’ and ‘Nirguna Brahman’ (Brahman without attributes).
Brahman (the existential substratum) is the only truth, the world is illusion, and there is ultimately no difference between Brahman and individual self.
Through the Advaita Vedanta, Shankara teaches us that Brahman is the only reality and that there is no separation between the soul and Brahman. Any apparent separation is illusion:
The fool thinks, “I am the body”; the intelligent man thinks, “I am an individual soul united with the body.” But the wise man, in the greatness of his knowledge and spiritual discrimination, sees the Self as the only reality and thinks, “I am Brahman.”
While the term ‘pantheism’ was not coined until 1697 (by mathematician Joseph Raphson), the ways in which the thought of Baruch Spinoza (the philosopher most often associated with pantheism) and Adi Shankara converge are remarkable. Writing not only in different languages but using entirely different conceptual and cultural frameworks, they arrived at comparable perceptions of the nature of reality and wisdom. Philosophical details diverge (never completely escaping their culture moorings), but both men saw the world as ultimately a single substance that they equated with God, and proposed ways of disciplining thought to overcome our perception of the world as the aggregation of individual substances.
That Reality is One; though, owing to illusion, It appears to be multiple names and forms, attributes and changes, It always remains unchanged. [It is] like gold which, while remaining one, is formed into various ornaments. You are that One, that Brahman. ~ Adi Shankara