The philosophy of the Upanishads, according to Paul Deussen, is the "culminating point of the Indian doctrine of the universe" and this point, he said, "had been already reached in Vedic, pre-Buddhistic times; and in philosophical significance has been surpassed by none of the later developments of thought up to the present day.". Paul Deussen published his brilliant German work Die Philosophic der Upanishads a century back in 1899, which was rendered into English by A.S. Geden in 1906. This rendering has been very much popular ever since despite the fact that the literature in English and other languages on the philosophy of the Upanishads has piled up considerably now. In view of the importance of Deussen's work, Geden's English rendering is herein reprinted on a persistent demand by the readers of Indian Philosophy.