Sankara wrote Bhashyas or commentaries on the Brahma Sutras, the Upanishads and the Gita. The Bhashya on the Brahma Sutras is called Sareerik Bhasya. Sankara wrote commentaries on Sanat Sujatiya and Sahasranama Adhyaya. It is usually said, “For learning logic and metaphysics, go to Sankara’s commentaries; for gaining practical knowledge, which unfolds and strengthens devotion, go to his works such as Viveka Chudamani, Atma Bodha, Aparoksha Anubhuti, Ananda Lahari, Atma-Anatma Viveka, Drik-Drishya Viveka and Upadesa Sahasri”. Sankara wrote innumerable original works in verses which are matchless in sweetness, melody and thought.
Sankara’s supreme Brahman is Nirguna (without the Gunas), Nirakara (formless), Nirvisesha (without attributes) and Akarta (non-agent). He is above all needs and desires. Sankara says, “This Atman is self-evident. This Atman or Self is not established by proofs of the existence of the Self. It is not possible to deny this Atman, for it is the very essence of he who denies it. The Atman is the basis of all kinds of knowledge. The Self is within, the Self is without, the Self is before and the Self is behind. The Self is on the right hand, the Self is on the left, the Self is above and the Self is below”.
Satyam-Jnanam-Anantam-Anandam are not separate attributes. They form the very essence of Brahman. Brahman cannot be described, because description implies distinction. Brahman cannot be distinguished from any other than He.
The objective world-the world of names and forms-has no independent existence. The Atman alone has real existence. The world is only Vyavaharika or phenomenal.
Sankara was the exponent of the Kevala Advaita philosophy. His teachings can be summed up in the following words:
Brahma Satyam Jagat Mithya,
Jeevo Brahmaiva Na Aparah
Brahman alone is real, this world is unreal; the Jiva is identical with Brahman.
Sankara preached Vivarta Vada. Just as the snake is superimposed on the rope, this world and this body are superimposed on Brahman or the Supreme Self. If you get a knowledge of the rope, the illusion of the snake will vanish. Even so, if you get a knowledge of Brahman, the illusion of the body and the world will vanish.
Sankara is the foremost among the master-minds and the giant souls which Mother India has produced. He was the expounder of the Advaita philosophy. Sankara was a giant metaphysician, a practical philosopher, an infallible logician, a dynamic personality and a stupendous moral and spiritual force. His grasping and elucidating powers knew no bounds. He was a fully developed Yogi, Jnani and Bhakta. He was a Karma Yogin of no mean order. He was a powerful magnet.
There is not one branch of knowledge which Sankara has left unexplored and which has not received the touch, polish and finish of his superhuman intellect. For Sankara and his works, we have a very high reverence. The loftiness, calmness and firmness of his mind, the impartiality with which he deals with various questions, his clearness of expression-all these make us revere the philosopher more and more. His teachings will continue to live as long as the sun shines.
Sankara’s scholarly erudition and his masterly way of exposition of intricate philosophical problems have won the admiration of all the philosophical schools of the world at the present moment. Sankara was an intellectual genius, a profound philosopher, an able propagandist, a matchless preacher, a gifted poet and a great religious reformer. Perhaps, never in the history of any literature, a stupendous writer like him has been found. Even the Western scholars of the present day pay their homage and respects to him. Of all the ancient systems, that of Sankaracharya will be found to be the most congenial and the most easy of acceptance to the modern mind.
Nisargadatta Maharaj - Teachings & Quotes 