Upanishad (Sanskrit) [from upa according to + ni down + the verbal root sad to sit] Following or according to the teachings which were received when sitting down; esoteric doctrine. "Literary works in which the rahasya -- a Sanskrit word meaning esoteric doctrine or mystery -- is imbodied. The Upanishads belong to the Vedic cycle and are regarded by orthodox Brahmans as a portion of the Sruti or 'Revelation.' It was from these wonderful quasi-esoteric and very mystical works that was later developed the highly philosophical and profound system called the Vedanta" (OG 179).
The Upanishads belong to the third division of the Vedas and are appended to the Brahmanas. The number of Upanishads hitherto known is about 170, though probably only a score are now complete without evident marks of excision or interpolation. These Upanishads belong to different periods of antiquity, some being of a much later date than others. Although the Upanishads are usually considered by modern scholars to be as a whole of later date than the Brahmanas, the original Upanishads were composed in an antiquity which anteceded that of the Brahmanas, and are probably coeval with the composition of the Vedas themselves.
"The Upanishads must be far more ancient than the days of Buddhism, as they show no preference for, nor do they uphold, the superiority of the Brahmans as a caste. On the contrary, it is the (now) second caste, the Kshatriya, or warrior class, who are exalted in the oldest of them.
to be continue "Upanishad2 "