Upanishad

108 Upanishads are known, of which the first dozen or so are the oldest and most important and are referred to as the principal or main (mukhya) Upanishads. The mukhya Upanishads are found mostly in the concluding part of the Brahmanas and Aranyakas and were, for centuries, memorized by each generation and passed down orally. The mukhya Upanishads predate the Common Era, but there is no scholarly consensus on their date, or even on which ones are pre- or post-Buddhist. The Brihadaranyaka is seen as particularly ancient by modern scholars. Of the remainder, 95 Upanishads are part of the Muktikā canon, composed from about the last centuries of 1st-millennium BCE through about 15th-century CE. New Upanishads, beyond the 108 in the Muktika canon, continued to be composed through the early modern and modern era, though often dealing with subjects that are unconnected to the Vedas. The mukhya Upanishads, along with the Bhagavad Gita and the Brahmasutra (known collectively as the Prasthanatrayi), are interpreted in divergent ways in the several later schools of Vedanta.