There is the atman not in man alone but in all objects of the universe, the sun, the moon, the world; and Brahman is this atman. There is nothing outside the atman, and therefore there is no plurality at all. As from a lump of clay all that is made of clay is known, as from an ingot of black iron all that is made of black iron is known, so when this atman the Brahman is known everything else is known. The essence in man and the essence of the universe are one and the same, and it is Brahman.
Now a question may arise as to what may be called the nature of the phenomenal world of colour, sound, taste, and smell. But we must also remember that the Upani@sads do not represent so much a conceptional system of philosophy as visions of the seers who are possessed by the spirit of this Brahman. They do not notice even the contradiction between the Brahman as unity and nature in its diversity. When the empirical aspect of diversity attracts their notice, they affirm it and yet declare that it is all Brahman. From Brahman it has come forth and to it will it return. He has himself created it out of himself and then entered into it as its inner controller (_antaryamin_). Here is thus a glaring dualistic trait of the world of matter and Brahman as its controller, though in other places we find it asserted most emphatically that these are but names and forms, and when Brahman is known everything else is known. No attempts at reconciliation are made for the sake of the consistency of conceptual utterance, as S'a@nkara the great professor of Vedanta does by explaining away the dualistic texts. The universe is said to be a reality, but the real in it is Brahman alone. It is on account of Brahman that the fire burns and the wind blows. He is the active principle in the entire universe, and yet the most passive and unmoved. The world is his body, yet he is the soul within. "He creates all, wills all, smells all, tastes all, he has pervaded all, silent and unaffected [Footnote ref 72]." He is below, above, in the back, in front, in the south and in the north, he is all this [Footnote ref 73]." These rivers in the east and in the west originating from the ocean, return back into it and become the ocean themselves, though they do not know that they are so. So also all these people coming into being from the Being do not know that they have come from the Being... That which is the subtlest that is the self, that is all this, the truth, that self thou art O S'vetaketu [Footnote ref 74]." "Brahman," as Deussen points out, "was regarded as the cause antecedent in time, and the universe as the effect proceeding from it; the inner dependence of the universe on Brahman and its essential identity with him was represented as a creation of the universe by and out of Brahman." Thus it is said in Mund. I.I. 7:
As a spider ejects and retracts (the threads),
As the plants shoot forth on the earth,
As the hairs on the head and body of the living man,
So from the imperishable all that is here.
As the sparks from the well-kindled fire,
In nature akin to it, spring forth in their thousands,
So, my dear sir, from the imperishable
Living beings of many kinds go forth,
And again return into him [Footnote ref 75].
Yet this world principle is the dearest to us and the highest teaching of the Upani@sads is "That art thou."
Again the growth of the doctrine that Brahman is the "inner controller" in all the parts and forces of nature and of mankind as the atman thereof, and that all the effects of the universe are the result of his commands which no one can outstep, gave rise to a theistic current of thought in which Brahman is held as standing aloof as God and controlling the world. It is by his ordaining, it is said, that the sun and moon are held together, and the sky and earth stand held together [Footnote ref 76]. God and soul are distinguished again in the famous verse of S'vetas'vatara [Footnote ref 77]:
Two bright-feathered bosom friends
Flit around one and the same tree;
One of them tastes the sweet berries,
The other without eating merely gazes down.
But in spite of this apparent theistic tendency and the occasional use of the word _Is'a_ or _Is'ana_, there seems to be no doubt that theism in its true sense was never prominent, and this acknowledgement of a supreme Lord was also an offshoot of the exalted position of the atman as the supreme principle. Thus we read in Kau@sitaki Upani@sad 3. 9, "He is not great by good deeds nor low by evil deeds, but it is he makes one do good deeds whom he wants to raise, and makes him commit bad deeds whom he wants to lower down. He is the protector of the universe, he is the master of the world and the lord of all; he is my soul (_atman_)." Thus the lord in spite of his greatness is still my soul. There are again other passages which regard Brahman as being at once immanent and transcendent. Thus it is said that there is that eternally existing tree whose roots grow upward and whose branches grow downward. All the universes are supported in it and no one can transcend it. This is that, "...from its fear the fire burns, the sun shines, and from its fear Indra, Vayu and Death the fifth (with the other two) run on [Footnote ref 78]."
If we overlook the different shades in the development of the conception of Brahman in the Upani@sads and look to the main currents, we find that the strongest current of thought which has found expression in the majority of the texts is this that the Atman or the Brahman is the only reality and that besides this everything else is unreal. The other current of thought which is to be found in many of the texts is the pantheistic creed that identifies the universe with the Atman or Brahman. The third current is that of theism which looks upon Brahman as the Lord controlling the world. It is because these ideas were still in the melting pot, in which none of them were systematically worked out, that the later exponents of Vedanta, S'a@nkara, Ramanuja, and others quarrelled over the meanings of texts in order to develop a consistent systematic philosophy out of them. Thus it is that the doctrine of Maya which is slightly hinted at once in B@rhadara@nyaka and thrice in S'vetas'vatara, becomes the foundation of S'a@nkara's philosophy of the Vedanta in which Brahman alone is real and all else beside him is unreal [Footnote ref 79].