The Upanishads are the sacred scriptures of the Hindus. The word, which means inner or mystic teaching, has been derived from 'Upa' which means near, 'Ni' or down and 'Shad' or to sit. This must refer to the ancient custom of groups of pupils sitting down near their teacher to learn the secret doctrine.
The Upanishads provide both spiritual vision and philosophical argument. They describe the core of spiritual experience which is incommunicable except by a way of life. The way to Ultimate Truth lies in personal efforts and the realization that the soul is one with all things of the Universe. The prime Vedic doctrines of Self-realization, Yoga and Meditation, Karma and Reincarnation are advocated by these sacred texts. They explicate all aspects of spirituality in detail, with examples, illustrations and stories.
Over a hundred Upanishads are known to the contemporary world. The most famous of these are the
Chandogya Upanishad, Aitareya Upanishad and
Taittiriya Upanishad. The Upanishads are considered the very essence of Vedanta (the end of Veda), because they offer the ultimate commentary on the Vedic philosophy. The older Upanishads, which probably date back to the 6th century BC, are usually part of a particular Veda, through a
Brahmin or Aranyaka. The later Upanishads are said to belong to the time of Buddha or after.
Hindu and Buddhist philosophies derive their teachings from the Upanishads. The great doctrine of 'neti-neti' of saint Yajnavalkya, which states that Truth can be found only through the negation of all thoughts, is based on Upanishadic principles. So is the famous 'Tatvamasi' which means 'You are That' (You are the Universe/ God). The greatest features of the Upanishads are their universal applicability and the total absence of dogmatism.