Indian religions have lots of philosophy and hundreds of scriptures with commentaries and commentaries on commentaries, which present a highly complicated picture especially in comparison to one-book-religion-cultures. The Upanishads form the most significant part of Indian philosophy and culture, regarded as the first ever philosophy in the world. There a couple of hundred Upanishads in all but the major ten or eleven present the chief concepts, and were therefore selected by the great Shankaracharya, to write commentaries upon, to promote his Advaita philosophy. Contents : Isha Upanishad Kena Upanishad Katha Upanishad Mundak Upannishad Prashna Upanishad Aitareya Upanishad Taittiriya Upanishad Kaushitaki Upanishad Chhandogya Upanishad Shvetasvatara Upanishad Brihadaranyaka Upanishad