The Philosophy of the Upanishads c5.s3.2

c5.s3.2

Many indications (of which more will be said hereafter) point to the fact that the leading ideas of the Upanishads, the doctrine, namely, of the sole reality of the Âtman, of its evolution as the universe, its identity with the soul, and so forth, although they may have originated from Brâhmans such as Yâjñavalkhya, yet in the earliest times met with acceptance rather in Kshatriya circles¹ than among Brâhmans, engrossed as the latter were in the ritual. It was only later on that they were adopted by the Brâhmans, and interwoven with the ritual on the lines of allegorical interpretation.