The dawn is the head of the sacrificial horse’, is composed for the sake of those who wish to liberate themselves from the world, in order that they many acquire the knowledge, that Brahman and the soul are the same, a knowledge, by which the liberation from the cause of the world is accomplished. This knowledge of Brahman is called Upanishad because it completely annihilates the world, together with its cause (ignorance) in such as possess this knowledge : for this is the meaning of the word Sad, proceeded by Upani. A work which treats on the same knowledge, is also called Upanishad.