The Upanisads are Philosophical and theological mystical treatises forming the third division of the Veda; the preceding portions being the Mantras or Hymans, which are largely prayers, and the Brahmanas or sacrificial rituals - the utterance, successively, of poet, priest and philosopher.
There are two great departments of the Veda. The first is called Karma-kanda, the department of works, which embraces both Mantras and Brahmanas; and is followed by the vast majority of persons whose actiojn of relition is laying up of merit by means of ceremonial prayers and sacrificial rites. The second is called Jnana-kanda, the department of knowledges - the theosophic portion of the Vedic revelation; and this is embraced by the Upanisads, and is intended for the select few who are capable of attaining the true doctrine. The most important of the Upanisads belong to what are called Arnyakas or forest-books, which form an appendix to the Brahmanas; and, treating as they do of the release of the soul from metapsychosis, by means of a recognition of the oneness of its real nature with the great impersonal Self, are so profound that they were required to be read in the solitude of forests, by persons, who, having performed all the duties of a student and a houe-holder, retired from the world to and their days in the contemplation of the Deity.
The Upanisads undoubtedly represent the highest product of the Indian mind; and one of the most imposing and subtle of the systems of ontology yet known in the history of philosophy; and the Vedanta, styled by Sankaracarya 'the string upon which the gems of the Upanisads are strung', is regarded as the finest flower and the ripest fruit of Indian spirituality. They contain the highest authority on which the various systems of Indian philosophy rest; and are practically the only portion of Vedic literature which is extensively studied by orthodox educated Hindus in the present day.
The Present Edition has been compiled with English translation of 112 important Upanisads many of which are being translated for the first time by a distinguished board of scholars. This edition provides an authentic translation of 112 Upanisads along with a complete index of verses and an exhaustive introduction.