The Philosophy of the Upanishads c6.s1.22

c6.s1.22

We may therefore assume that the doctrine of the âtman as the first principle of the universe, the gradual rise of which we have traced through the hymns of the Ṛigveda and Atharvaveda, was fostered and progressively developed by the Kshatriyas in opposition to the principles of the Brâhmanical ritual; whence the new knowledge was expressed in brief words or formulas, intelligible only to the initiated, such as tadvanam, tajjalân, satyasya satyam, samyadvâma, vâmaní, bhâmaní, etc. A formula of this kind was then called an upanishad, inasmuch as the condition of its communication and explanation was the absence of publicity. Such formulas were naturally accompanied by oral explanations, which also were kept secret, and from these were gradually developed the earliest texts that bore the name of Upanishad. The manner in which the formulas tad vai tad¹ or vi-ram² are discussed may serve as examples of such secret words accompanied by secret explanation.³