The teachings of Sankara can be summed up in half a verse: “Brahma Satyam Jagan Mithya Jivo Brahmaiva Na Aparah—Brahman (the Absolute) is alone real; this world is unreal; and the Jiva or the individual soul is non-different from Brahman.” This is the quintessence of his philosophy.
The Advaita taught by Sri Sankara is a rigorous, absolute one. According to Sri Sankara, whatever is, is Brahman. Brahman Itself is absolutely homogeneous. All difference and plurality are illusory.
Brahman—The One Without A Second
The Atman is self-evident (Svatah-siddha). It is not established by extraneous proofs. It is not possible to deny the Atman, because It is the very essence of the one who denies It. The Atman is the basis of all kinds of knowledge, presuppositions and proofs. Self is within, Self is without; Self is before, Self is behind; Self is on the right, Self is on the left; Self is above and Self is below. Brahman is not an object, as It is Adrisya, beyond the reach of the eyes. Hence the Upanishads declare: “Neti Neti—not this, not this….” This does not mean that Brahman is a negative concept, or a metaphysical abstraction, or a nonentity, or a void. It is not another. It is all-full, infinite, changeless, self-existent, self-delight, self-knowledge and self-bliss. It is Svarupa, essence. It is the essence of the knower. It is the Seer (Drashta), Transcendent (Turiya) and Silent Witness (Sakshi). Sankara’s Supreme Brahman is impersonal, Nirguna (without Gunas or attributes), Nirakara (formless), Nirvisesha (without special characteristics), immutable, eternal and Akarta (non-agent). It is above all needs and desires. It is always the Witnessing Subject. It can never become an object as It is beyond the reach of the senses. Brahman is non-dual, one without a second. It has no other beside It. It is destitute of difference, either external or internal. Brahman cannot be described, because description implies distinction. Brahman cannot be distinguished from any other than It. In Brahman, there is not the distinction of substance and attribute. Sat-Chit-Ananda constitute the very essence or Svarupa of Brahman, and not just Its attributes. The Nirguna Brahman of Sankara is impersonal. It becomes a personal God or Saguna Brahman only through Its association with Maya. Saguna Brahman and Nirguna Brahman are not two different Brahmans. Nirguna Brahman is not the contrast, antithesis or opposite of Saguna Brahman. The same Nirguna Brahman appears as Saguna Brahman for the pious worship of devotees. It is the same Truth from two different points of view. Nirguna Brahman is the higher Brahman, the Brahman from the transcendental viewpoint (Paramarthika); Saguna Brahman is the lower Brahman, the Brahman from the relative viewpoint (Vyavaharika).
The World—A Relative Reality
The world is not an illusion according to Sankara. The world is relatively real (Vyavaharika Satta), while Brahman is absolutely real (Paramarthika Satta). The world is the product of Maya or Avidya. The unchanging Brahman appears as the changing world through Maya. Maya is a mysterious indescribable power of the Lord which hides the real and manifests itself as the unreal: Maya is not real, because it vanishes when you attain knowledge of the Eternal. It is not unreal also, because it exists till knowledge dawns in you. The superimposition of the world on Brahman is due to Avidya or ignorance.
Nature Of The Jiva And The Means To Moksha
To Sankara, the Jiva or the individual soul is only relatively real. Its individuality lasts only so long as it is subject to unreal Upadhis or limiting conditions due to Avidya. The Jiva identifies itself with the body, mind and the senses, when it is deluded by Avidya or ignorance. It thinks, it acts and enjoys, on account of Avidya. In reality it is not different from Brahman or the Absolute. The Upanishads declare emphatically: “Tat Tvam Asi—That Thou Art.” Just as the bubble becomes one with the ocean when it bursts, just as the pot-ether becomes one with the universal ether when the pot is broken, so also the Jiva or the empirical self becomes one with Brahman when it gets knowledge of Brahman. When knowledge dawns in it through annihilation of Avidya, it is freed from its individuality and finitude and realises its essential Satchidananda nature. It merges itself in the ocean of bliss. The river of life joins the ocean of existence. This is the Truth. The release from Samsara means, according to Sankara, the absolute merging of the individual soul in Brahman due to dismissal of the erroneous notion that the soul is distinct from Brahman. According to Sankara, Karma and Bhakti are means to Jnana which is Moksha.
More Info: Shankarachaya Advaita Vedanta Portal