the teachers who are credited with the doctrines of the Upanishads manifestly belonged to different sections of Brahminical society, to different Vedic sakhas; nay, some of them the tradition makes out to have been kshattriyas.  And, in the second place, the period, whose mental activity is represented in the Upanishads, was a creative one, and as such cannot be judged according to the analogy of later periods of Indian philosophic development.  The later philosophic schools as, for instance, the one of which Sa@nkara is the great representative, were no longer free in their speculations, but strictly bound by a traditional body of texts considered sacred, which could not be changed or added to, but merely systematised and commented upon.  Hence the rigorous uniformity of doctrine characteristic of those schools.  But there had been a time when, what later writers received as a sacred legacy, determining and confining the whole course of their speculations, first sprang from the minds of creative thinkers not fettered by the tradition of any school, but freely following the promptings of their own heads and hearts.  By the absence of school traditions, I do not indeed mean that the great teachers who appear in the Upanishads were free to make an entirely new start, and to assign to their speculations any direction they chose; for nothing can be more certain than that, at the period as the outcome of whose philosophical activity the Upanishads have to be considered, there were in circulation certain broad speculative ideas overshadowing the mind of every member of Brahminical society.  But those ideas were neither very definite nor worked out in detail, and hence allowed themselves to be handled and fashioned in different ways by different individuals.  With whom the few leading conceptions traceable in the teaching of all Upanishads first originated, is a point on which those writings themselves do not enlighten us, and which we have no other means for settling; most probably they are to be viewed not as the creation of any individual mind, but as the gradual outcome of speculations carried on by generations of Vedic theologians.  In the Upanishads themselves, at any rate, they appear as floating mental possessions which may be seized and moulded into new forms by any one who feels within himself the required inspiration.  A certain vague knowledge of Brahman, the great hidden being in which all this manifold world is one, seems to be spread everywhere, and often issues from the most unexpected sources. Svetaketu receives instruction from his father Uddalaka; the proud Gargya has to become the pupil of Ajata/s/atru, the king of Ka/s/i; Bhujyu Sahyayani receives answers to his questions from a Gandharva possessing a maiden; Satyakama learns what Brahman is from the bull of the herd he is tending, from Agni and from a flamingo; and Upako/s/ala is taught by the sacred fires in his teacher’s house.  All this is of course legend, not history; but the fact that the philosophic and theological doctrines of the Upanishads are clothed in this legendary garb certainly does not strengthen the expectation of finding in them a rigidly systematic doctrine.