From the objective sides this ultimate reality is called Brahman. The word is derived from the root ‘Brh’ which means to grow or to evolve. In the beginning it meant sacrifice, then prayer and then it acquired its present meaning of ultimate reality which evolves itself as this world. Brahman is that which spontaneously bursts forth as nature and soul. It is the ultimate cause of this universe. In the Chhandogya, it is cryptically described as ‘Tajjalan’—as that from which the world arises into which it returns, and by which it is supported and it lives. In the Taittiriya, Brahman is defined as that from which all these beings are born by which they live, and into which they are reabsorbed. The evolution of the elements is given in this order: From Brahman arises ether, from ether air, from air fire, from fire water, from water earth. But the real theory of evolution is given in the doctrine of the five sheaths ( koshas ) in the Taittiriya :

 The first and the lowest level is that of matter ( annamaya ). Matter is unconscious and dead and cannot account for life. It is purely on the physical plane. Brahman cannot rest content with matter. The purpose of matter is fulfilled only when life is evolved. This highest state of matter is therefore life. Though matter cannot account for life, yet there can be no life without matter. The inorganic matter must be transformed into organic life.

Hence, the second state of evolution is life ( pranayama ). Now we are on the biological plane. The vegetable life ( osadhayah ) emerges first. But the vegetable life must lead to the animal life. The vegetable products must be transformed into living animal cells. Life pervades the universe and binds man with the rest of creation. But the destiny of life is fulfilled only when consciousness is evolved.

Hence, the third state of evolution is mind or perceptual Consciousness ( manomaya ). Here we are on the mental or psychological plane. This state is shared by lower animals with man. Mind or consciousness remains in the lower animal life at the level of instinct and reflex action. Human being have got instincts and reflex actions and these play an important part in the determining thee human life. But brute instinct is mute and rebels against itself. It wants to express itself. It is on the level of infra-relational undifferentiated feeling. The subject – object duality is absent here because it has not yet been evolved. The end of this instinctive consciousness will be fulfilled only when a higher principle has been evolved where consciousness become self – conscious or rational.

Hence, the forth state of evolution is self – conscious reason ( vijnanamaya ). Here we are on the metaphysical plane. This state is the soul monopoly of human beings. Reason becomes self – conscious only at this state and this fact distinguishes human beings from lower animas. Arts, science, aesthetics, morals, poetry, philosophy, religion, all become possible only at this state. The empirical trinity of knower, knowledge and known has been evolved. But even this will not suffice. There is a higher experience of which we get a negative glimpse in the empirical life and which cannot be accounted for by mere intellect. The relational and analytical, the discursive and dichotomous intellect points to something higher as its end in which it wants to merge itself. The subject – object duality wants to transcend itself; not that it wants to fall back on the instinctive undifferentiated feeling which it has left far behind, but it wants to fulfill its destiny by merging itself in the absolute, the abode of bliss, where there is no trace of duality and plurality.

The fifth and the highest state of evolution, therefore, is the non dual bliss. Here we are on the mystic plane. The empirical trinity of knower, known and knowledge has been fused into a transcendental unity. Here philosophy terminates. This brahman, the supreme reality, transcends all, yet it underlies all as their background. The lower is not lost or annihilated; it is simply transformed in the higher. Matter is not lost in life; life is not lost in mind; mind is not lost in reason; reason is not lost in bliss. Brahman pervades them all. It is the immanent inner controller of all and the self of all. As all spokes are contained in the axle and the wheel, so all beings, all gods, all worlds, all organs are contained in the Universal self, the Brahman. This is the Brahman the self – luminous, the immortal, the support of all the worlds, the highest and leaving nothing beyond it. Matter is its body, it is its soul; the individual souls are its body, it is their soul. It holds the self and the non-self together which are equally its own manifestations and yet in its own  nature it transcends both.