The Upanishads are ancient, sacred texts that form the final part of Hindu religious thought. The Sanskrit word ‘Upanishad’ literally means to sit at the feet of a master to receive instruction. Chronologically, they follow the Vedas and are often referred to as the Vedanta (‘veda’, knowledge and ‘anta’, end or conclusion) for this reason. Of the approximately 108 existing Upanishads, twelve are considered to be the core teachings. They take the form of dialogues, with each discoursing on a metaphysical, moral or teleological theme. In brief, the thought in the Upanishads is concerned with the Brahman (universal soul) and the Atman (individual soul) and the relationship between the two. The Brahman is the all encompassing plane of being that acts as the informing principle of all other existence.
As with any religious text, exegeses of the Upanishads are many and are informed by differing metaphysical and religious beliefs; the principal commentaries, however, are to be found in the writings of Shankara, Madhvacharva and Vishishtadvaita. The most salient differences between these various schools is to be discerned in how they regard the metaphysical status of Brahman. Shankara and Madvacharva differ most obviously in this regard, for the former postulates that Brahman is limitless and beyond temporal notions of being, while the latter positions Brahman in the pantheon along with gods such as Vishnu and Krishna.
The Upanishads record the thoughts and philosophical musings of a succession of Hindu teachers and sages who worked around 1000BC, but who were particularly prominent in 600BC. It has been speculated that the Upanishads from the earlier period form part of Brahmanas (commentaries) of their respective Vedas, yet they are to be distinguished from them because the bias of their enquiry is more philosophical and mystical and conversely they pay less attention to the deities of the Vedas and their associated sacrificial rites.
The influence of the Upanishads isn’t limited to Hinduism. They are known to have been studied by Jains and Buddhists. Equally, during the Middle Ages, Muslim scholars such as Dara Shikoh, the elder son of Shajahan, were influenced by Hindu philosophy and the Upanishads in particular. He had a number of the Upanishads translated into his native Persian. However, it was with the establishment of the British Raj in India and the well regarded translations made by German Philologist Max Muller that the Upanishads met with a large European audience.