The best opinion of India has always felt that the way of knowledge or Jnana was the true way.  The favourite thesis of the Brahmans was that a man should devote his youth to study, his maturity to the duties and ceremonies of a householder, and his age to more sublime speculations.  But at all periods the idea that it was possible to know God and the universe was allied to the idea that all ceremonies as well as all worldly effort and indeed all active morality are superfluous[169].  All alike are unessential and trivial, and merit the attention only of those who know nothing higher.  Human feelings and interests qualified and contradicted this negative and unearthly view of religion, but still popular sentiment as well as philosophic thought during the whole period of which we know something of them in India tended to regard the highest life as consisting in rapt contemplation or insight accompanied by the suppression of desire and by disengagement from mundane ties and interests.  But knowledge in Indian theology implies more intensity than we attach to the word and even some admixture of volition.  The knowledge of Brahman is not an understanding of pantheistic doctrines such as may be obtained by reading The Sacred Books of the East in an easy chair but a realization (in all senses) of personal identity with the universal spirit, in the light of which all material attachments and fetters fall away.

The earlier philosophical speculations of the Brahmans are chiefly found in the treatises called Upanishads.  The teaching contained in these works is habitually presented as something secret[170] or esoteric and does not, like Buddhism or Jainism, profess to be a gospel for all.  Also the teaching is not systematized and has never been unified by a personality like the Buddha.  It grew up in the various parishads, or communities of learned Brahmans, and perhaps flourished most in north western India[171].  There is of course a common substratum of ideas but they appear in different versions:  we have the teaching of Yajnavalkya, of Uddalaka Aruni and other masters and each teaching has some individuality.  They are merely reported as words of the wise without an attempt to harmonize them.  There are many apparent inconsistencies due to the use of divergent metaphors to indicate different aspects of the indescribable, and some real inconsistencies due to the existence of different schools.  Hence, attempts whether Indian or European to give a harmonious summary of this ancient doctrine are likely to be erroneous.

There are a great number of Upanishads, composed at various dates and not all equally revered.  They represent different orders of ideas and some of the later are distinctly sectarian.  Collections of 45, 52 and 60 are mentioned, and the Muktika Upanishad gives a list of 108.  This is the number currently accepted in India at the present day.  But Schrader[172] describes many Upanishads existing in MS. in addition to this list and points out that though they may be modern there is no ground for calling them spurious.  According to Indian ideas there is no a priori objection to the appearance now or in the future of new Upanishads[173].  All revelation is eternal and self-existent but it can manifest itself at its own good time.