The sum and substance of the Upani@sad teaching is involved in the equation Atman=Brahman. We have already seen that the word Atman was used in the @Rg-Veda to denote on the one hand the ultimate essence of the universe, and on the other the vital breath in man. Later on in the Upani@sads we see that the word Brahman is generally used in the former sense, while the word Atman is reserved to denote the inmost essence in man, and theUpani@sads are emphatic in their declaration that the two are one and the same. But what is the inmost essence of man? The self of man involves an ambiguity, as it is used in a variety of senses. Thus so far as man consists of the essence of food (i.e. the physical parts of man) he is called _annamaya_. But behind the sheath of this body there is the other self consisting of the vital breath which is called the self as vital breath (_pra@namaya atman_). Behind this again there is the other self "consisting of will" called the _manomaya atman_. This again contains within it the self "consisting of consciousness" called the _vijnanamaya atman_. But behind it we come to the final essence the self as pure bliss (the _anandamaya atman_). The texts say: "Truly he is the rapture; for whoever gets this rapture becomes blissful. For who could live, who could breathe if this space (_akas'a_) was not bliss? For it is he who behaves as bliss. For whoever in that Invisible, Self-surpassing, Unspeakable, Supportless finds fearless support, he really becomes fearless. But whoever finds even a slight difference, between himself and this Atman there is fear for him [Footnote ref 69]."
Again in another place we find that Prajapati said: "The self (_atman_) which is free from sin, free from old age, from death and grief, from hunger and thirst, whose desires are true, whose cogitations are true, that is to be searched for, that is to be enquired; he gets all his desires and all worlds who knows that self [Footnote ref 70]." The gods and the demons on hearing of this sent Indra and Virocana respectively as their representatives to enquire of this self from Prajapati. He agreed to teach them, and asked them to look into a vessel of water and tell him how much of self they could find. They answered: "We see, this our whole self, even to the hair, and to the nails." And he said, "Well, that is the self, that is the deathless and the fearless, that is the Brahman." They went away pleased, but Prajapati thought, "There they go away, without having discovered, without having realized the self." Virocana came away with the conviction that the body was the self; but Indra did not return back to the gods, he was afraid and pestered with doubts and came back to Prajapati and said, "just as the self becomes decorated when the body is decorated, well-dressed when the body is well-dressed, well-cleaned when the body is well-cleaned, even so that image self will be blind when the body is blind, injured in one eye when the body is injured in one eye, and mutilated when the body is mutilated, and it perisheswhen the body perishes, therefore I can see no good in this theory." Prajapati then gave him a higher instruction about the self, and said, "He who goes about enjoying dreams, he is the self, this is the deathless, the fearless, this is Brahman." Indra departed but was again disturbed with doubts, and was afraid and came back and said "that though the dream self does not become blind when the body is blind, or injured in one eye when the body is so injured and is not affected by its defects, and is not killed by its destruction, but yet it is as if it was overwhelmed, as if it suffered and as if it wept--in this I see no good." Prajapati gave a still higher instruction: "When a man, fast asleep, in total contentment, does not know any dreams, this is the self, this is the deathless, the fearless, this is Brahman." Indra departed but was again filled with doubts on the way, and returned again and said "the self in deep sleep does not know himself, that I am this, nor does he know any other existing objects. He is destroyed and lost. I see no good in this." And now Prajapati after having given a course of successively higher instructions as self as the body, as the self in dreams and as the self in deep dreamless sleep, and having found that the enquirer in each case could find out that this was not the ultimate truth about the self that he was seeking, ultimately gave him the ultimate and final instruction about the full truth about the self, and said "this body is the support of the deathless and the bodiless self. The self as embodied is affected by pleasure and pain, the self when associated with the body cannot get rid of pleasure and pain, but pleasure and pain do not touch the bodiless self [Footnote ref 71]."
As the anecdote shows, they sought such a constant and unchangeable essence in man as was beyond the limits of any change. This inmost essence has sometimes been described as pure subject-object-less consciousness, the reality, and the bliss. He is the seer of all seeing, the hearer of all hearing and the knower of all knowledge. He sees but is not seen, hears but is not heard, knows but is not known. He is the light of all lights. He is like a lump of salt, with no inner or outer, which consists through and through entirely of savour; as in truth this Atman has no inner or outer, but consists through and through entirely of knowledge. Bliss is not an attribute of it but it is bliss itself. The state of Brahman is thus likened unto the state of dreamless sleep. And he who has reached this bliss is beyond any fear. It is dearer to us thanson, brother, wife, or husband, wealth or prosperity. It is for it and by it that things appear dear to us. It is the dearest _par excellence_, our inmost Atman. All limitation is fraught with pain; it is the infinite alone that is the highest bliss. When a man receives this rapture, then is he full of bliss; for who could breathe, who live, if that bliss had not filled this void (_akas'a_)? It is he who behaves as bliss. For when a man finds his peace, his fearless support in that invisible, supportless, inexpressible, unspeakable one, then has he attained peace.