homogeneous, or unified philosophical system, though there are certain
doctrines held in common. Divergences of method, opinion, and conclusion
are everywhere apparent even within a single Upanishad. It is for this reason
that the Upanishads are considered speculative treatises.
     Another significant feature of the Upanishads, particularly the older ones,
is that practically every basic idea expounded has its antecedent in earlier
Vedic texts. What distinguishes the Upanishads is not so much their
originality as their probing for new interpretations of the earlier Vedic
concepts to obtain a more coherent view of the universe and man. Here the
link between man and the cosmos is, as we have said, no longer the ritual act,
but a knowledge of the forces symbolically represented in the ritual.
  Important Concepts The idea of rebirth as such appears first in a
  supplementary section of the Brihadaranyaka Upanishad and also in a
  slightly fuller form in the Chandogya Upanishad, the two oldest
  Upanishads. Besides, the Brihadaranyaka Upanishad presents the view
  that repeated death (mrityu)—a concept first appearing in the Brahmanas
  —is something which the possessor of certain kinds of knowledge can
  ward off.
  The doctrine of the cosmic self (vaisvanara atman) is taught in several
  stories in the Chandogya Upanishad. One of them tells us of five
  householders who, along with the great philosopher Uddakala Aruni, go to
  the philosopher-king, Asvapati of Kekaya, seeking knowledge of the self.
  But the most important episode in the Chandogya is the one in which
  Uddakala teaches his son, Svetaketu, the truth of the non-difference of the
  individual soul from the Brahmana.
Vedangas and Sutra Literature
There are six Vedangas: (I) Siksha (Phonetics), (2) Kalpa (Rituals), (3)
Vyakarna (Grammar), (4) Nirukta (Etymology), (5) Chandas (Metrics) and
(6) Jyotisha (Astronomy). In contrast to the Vedic literature proper, which is
considered sruti or divine revelation, the Vedangas are called smriti or
literature handed down by tradition because they are of human origin.
     The Vedangas are written in