In this chapter one learns about the Supreme Person refereed to as Purusha. Krishna uses the metaphor of a big banyan tree to explain the transitory nature of the world.
The big banyan tree, the Ashwattha, is said to be eternal with its roots above in the Supreme and branches downward. The Vedas are its leaves. He who has fathomed the depths of the ever-changing and ever-evolving world has all the Vedic knowledge at his disposal.
The branches of this tree spread downward and upward getting nourishment from the Gunas. Sense objects are its twigs and this tree is caught by its own action and reaction in this world of ours. This tree is unlike any earthly tree. Its end, beginning or its foundations are not seen. Then Sri Krishna goes on to say that, ?Using the sword of non-attachment one must cut off this firm-rooted Asvattha tree and search for that state from which there is no return. He should do this search saying, ?I seek refuge only in the Primal Person from whom has come forth this ancient current of the world.?
Krishna now describes the attitude and efforts required to attain that state.?Those who are free from pride and delusion, who have conquered the evil of attachment, whose all desires are conquered, who are ever devoted to the Supreme Spirit, who have escaped from the dualities pain and pleasure and who are free from confusion, attain to that eternal state.? (15.5)
The Lord declares: ?those who reach My abode never return. Neither Sun nor the Moon nor the fire illumines it.?
Sri Krishna explains that He is the life of the universe, ?The sages practicing spiritual discipline see Me situated in the self but those who have not realized the self and whose minds are not developed can not see Me, howsoever they may try. I am seated in the hearts of all. From me are born memory and knowledge and it is I who destroy them. I am alone the object of the Vedas, I am indeed the author of the Vedanta and I too the knower of the Vedas.? (15.11, 15.15)
Sri Krishna says there are two aspects of creation: the perishable and the imperishable. Beyond these two is the Impersonal Supreme. This Impersonal Supreme is at once all-pervading and all-sustaining.?I, the Purusottama, the Supreme Being, transcend both the perishable and the imperishable? (15.18)
(The following English translation is taken from ‘A Sourcebook in Indian Philosophy’ Edited by S. Radhakrishnan and Charles A. Moore. 1957 Princeton University Press)
Chapter 15: The Tree of Life
The cosmic tree
The Blessed Lord said:
1.They speak of the imperishable asvattham (peepal tree) as having its root above and branches below. Its leaves are the Vedas and he who knows this is the knower of the Vedas*.
2. Its branches extend below and above, nourished by the modes, with sense objects for its twigs; and below, in the world of men, stretch forth the roots resulting in actions.
3. Its real form is not thus perceived here, nor its end nor beginning nor its foundation. Having cut off this firm-rooted asvattham (peepal tree) with the strong sword of non-attachment.
4. Then, that path must be sought from which those who have reached it never return, saying, ?I seek refuge only in that Primal Person from whom has come forth this ancient current of the world? [this cosmic process].
5. Those who are freed from pride and delusion, who have conquered the evil of attachment, who, all desires stilled, are ever devoted to the Supreme Spirit, who are liberated from the dualities of pleasure and pain and are undeluded, go to that eternal state.
Manifested life is only a part
6. The sun does not illumine that, nor the moon nor the fire. That is My supreme abode from which those who reach it never return.
The Lord as the life of the universe
7. A fragment [or fraction] of My own self, having become a living soul, eternal, in the world of life, draws to itself the senses of which the mind is the sixth, that rest in nature.
8. When the lord takes up a body and when he leaves it, he takes these [the senses and mind] and goes even as the wind carries perfumes from their places.
9. He enjoys the objects of the senses, using the ear, the eye, the touch sense, the taste sense, and the nose as also the mind.
10. When He departs or stays or experiences, in contact with the modes, the deluded do not see [the indwelling soul] but they who have the eye of wisdom [or whose eye is wisdom] see.
11. The sages also striving perceive Him as established in the self, but the unintelligent, whose souls are undisciplined, though striving, do not find Him.
12. That splendour of the sun that illumines this whole world, that which is in the moon, that which is in the fire, that splendour, know as Mine.
13. And entering the earth, I support all beings by My vital energy; and becoming the sapful soma [moon], I nourish all herbs [or plants].
14. Becoming the fire of life in the bodies of living creatures and mingling with the upward and downward breaths, I digest the four kinds of food.
15. And I am lodged in the hearts of all; from Me are memory and knowledge as well as their loss. I am indeed He who is to be known by all the Vedas. I indeed [am] the author of the Vedanta and I too the knower of the Vedas.
The Supreme Person
16. There are two persons in this world, the perishable and the imperishable; the perishable is all these existences and the unchanging is the imperishable.
17. But other than these, the Highest Spirit called the Supreme Self who, as the Undying Lord, enters the three worlds and sustains them.
18. As I surpass the perishable and am higher even than the imperishable, I am celebrated as the Supreme Person in the world and in the Veda.
19. He who, undeluded, thus knows Me, the Highest Person, is the knower of all and worships Me with all his being [with his whole spirit], 0 Bharata (Arjuna).
20. Thus has this most secret doctrine been taught by Me, 0 blameless one. By knowing this, a man will become wise and will have fulfilled all his duties, 0 Bharata (Arjuna).
This is the fifteenth chapter entitled ?The Yoga of the Supreme Person.?
* The world is a living organism united with the Supreme. According to ancient belief, the Vedic sacrificial cult is said to sustain the world and so the hymns are said to be the leaves which keep the tree with its trunk and branches alive.