The Upanisads are philosophical and theological mystical treatises forming the third division of the Veda; the preceding portions being the Mantras or Hymns, 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 action of religion 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 Upanisads belong to what are called Aranyakas or forest-books, which form an appendix to the Brahmanas; and, treating as they do of the release of the soul from metaphsychosis, by means of a recognition of the oneness of its real nature with the great impersonal Self and 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 house-holder, retired from the world and their days passed in the contemplation of the Deity.
The Upanisads are as far removed from the ancient poetry of the Veda as the Talmud is from the Old Testament and Sufism is from the Quran. They represent the results of the first plunge of the human mind into the depths of metaphysical speculation; and investigate such abstruse problems as the origin of the universe, the nature of the Deity, the nature of the human soul, and the relation of spirit and matter.
The etymology of the word is doubtful. It probably signifies sitting down near somebody, in order to listen or meditate and worship (Upa-ni-sad); so that it would express the idea of a session or assembly of pupils sitting down at a respectful distance secret doctrine-a digest of the principles and mysteries contained in the Vedas; and some Indian philosophers derive the word from the root sad, in the sense of destruction; meaning thereby that the secret doctrine, fully apprehended, would destroy all passion and ignorance, and all knowledge derived from the senses merely-all knowledge save that of the Self.