We know from references in the Rig Veda that the religious practices of the invading Aryans included use of a presumably hallucinogenic substance known as soma.   In following centuries soma was no longer used, but sometime in that period various individuals appeared to have discovered that through ascetic practices such as fasting and sleep deprivation and prolonged meditation (usually understood as an effort to turn off both sensation and thought) it was possible to achieve some of the same psychological effects.  These included a loss of any sense of personal identity, which then allowed a sense of blissful absorption into a different type of reality--an undifferentiated and seemingly unlimited consciousness.  We generally refer to this as a mystical experience, and today there are various terms used to describe it (cosmic consciousness, for example). 

Gradually a culture developed among these individuals, who typically left their families and villages to live in the forest.  Older ascetics took on apprentices, and in time an oral teaching learned by those sitting at the feet of the masters (the literal meaning of the term upanishad) came to be recorded.   In this teaching, understandably not to be divulged to outsiders, the ordinary view of what the universe was all about--a metaphysical ladder of gods and demons and mortals and ghosts and whatever else--came to be redefined.  Human beings had their own souls which could only expect a series of repeated incarnations until suffiently purified to be released from the wheel of rebirth, but the deeper truth was that within each individual there was another spiritual reality that was finally identical to the ultimate reality of the universe itself.  There was jiva (the personal soul), the atman (the spiritual core), and brahman (ultimate reality also thought of as Satchitananda--Existence, Consciousness, and Bliss), and the secret truth was that atman and brahman were the same.  My atman is like a bit of the spray of the endless ocean that is brahman, but the illusion maintained through my jiva is that I am ultimately distinct.  Breaking through that illusion is the entire purpose of a life more intensely dedicated to the pursuit of moksha (liberation).  The saying that "the That is Yourself" (tat tvam asi) was to become something actually experienced. 

The idea that this teaching would have reflected an awareness based on actual experience is one thing that continues to set Hindu and Buddhist thought apart from what we are familiar with in the West.  For us, spiritual practices are usually based on an idea of faith or an acceptance of something not to be experienced until after death.  For the person following the deeper practices of Hindu and Buddhist tradition, the goal is a "unitive experience'' --the bliss of samadhi--in this lifetime.  Initially this was through a more extreme asceticism, but in time, especially with the Buddhists, techniques of meditation were given greater emphasis.  The teacher (guru) was someone who had achieved this goal for himself, which might be recognized by his showing various supernatural abilities (siddhis) as though by seeing past the illusion that we take to be the "real" world he has achieved a godlike ability to change things within the illusion.


As time went on, different schools of philosophy developed to make sense of how we should talk about the teachings presented in the Upanishads.  Two main approaches appeared.  One insisted on a dualism in which the entire natural world (including our minds) was activated by, as it were, atoms of consciousness that themselves were unchanged. Prakriti (the natural world) and purusha (these atoms of consciousness) are both eternal, but the ultimate truth is that my individual purusha needs to be liberated from the bond.  This is accomplished by systematically having my consciousness strip itself of all physical awareness and then finally of all thought until the glistening diamond of my purusha is allowed a full self-realization.  In other words, when I let go of "me" (the self that I think I am) I blissfully get to know my true self.  I do not then have to keep coming back life after life.  This is the teaching expressed in the closely related schools of Samkhya and Yoga, both of which technically are "atheist" in that there is no divinity beyond this interplay of purusha and prakriti.

A quite different approach, which came into prominence in part as a response to Buddhism, is Vedanta.  This is a monist teaching which stressed that there was but the single reality of brahman, which is manifested in all that we take to be real as the playful expression (lila) of an ultimate joyfulness.  Imagine a beautiful woman admiring herself in a set of mirrors displaying her from different angles.  She is enjoying the show she puts on.  What happens though is that the reflections in the mirrors make the mistake of thinking they are real in their own right.  What they need to do is let go of this false sense of being an independent self, which is ultimately a result of ignorance (avidya), and then there is just the bliss of the woman herself.

One question coming up was how to reconcile ordinary religious practices--all the sacrifices and devotional activities that were part of village life--with this deeper teaching.  Should not the student in his effort to see everything as maya reject these "superstitions"?   Shankara, one of the great Vedantist teachers, answered this by talking about how someone walking along a forest trail suddenly sees a snake hanging down.  He is frightened but knows he must still go down this path.  As he gets closer, though, he realizes that what he had thought to be a terrifying snake (a boa constrictor, say) was only a thick vine, a rope--not something to be afraid of at all.  Now the point is that he was not wrong in his initial response.  He did not yet know better and so he acted appropriately.