Themes and concepts that are essential to the proper understanding and practice of yoga are introduced briefly in early chapters of the Bhagavad-gītā; then in later chapters these same themes receive elaboration. This we have seen in particular with the principles of sāṅkhya (analysis) and dhyāna (meditation). Similarly, we have already been introduced to the notion of bhagavān (literally, the possessor of plenitude) in earlier chapters, and this notion is dramatically and graphically demonstrated to Arjuna in Chapter 11. Now again in this fifteenth chapter (or fifteenth discourse on yoga), attention is directed to bhagavān, here referred to as puruṣottama, the ultimate person, to fill out the notion of spirit-as-person in important ways.
Initially, however, Krishna continues from the previous chapter the subject of modalities. To make clear the necessity to become free from the modalities by firm acts of detachment, he provides a striking analogy: Krishna invites us to picture a “nonperishing banyan tree”—an analogy for the temporal world that is drawn from the experience of temporal banyan trees—with roots reaching upward and branches extending both downward and upward. The nonperishing tree’s branches (which represent varieties of mundane Vedic knowledge, composed in hymns which are the tree’s leaves) thrive on nature’s modalities (the three guṇas). This tree holds captive all embodied beings in endlessly entangled worldly existence: one can trace out neither this tree’s beginning nor its end. How could one possibly become truly free from this “tree” of captivity? The only way to become free from this tree is to forcefully cut it down “with the weapon of detachment.” For such a detached and unconfused yogī it becomes possible to seek out that place beyond the temporal world from which one never returns. And what sort of place is that atemporal realm? It is radically different from this temporal world: Krishna hints at the self-luminous nature of the non-material realm, describing it as one which is illuminated neither by sun, nor moon, nor fire (15.1-6).
But one doubt might linger in the reader’s mind: “Is it not possible, somehow, to attain the atemporal realm without all the effort of practicing yoga.” No, it is not possible to escape simply by wishing to do so. To better understand the situation, one must better understand the process of transmigration. Krishna has alluded to the process of transmigration already in Chapter 2. Now he elaborates briefly on how it works. All beings, although eternal “parts” (aṁśa) of bhagavān (and are therefore also “masters”), obtain in this world particular bodies in accordance with their desires for pleasure, and according to their previous actions. Then they quit their bodies to take others. While in a particular body, a living being encounters the various sense objects which that body’s senses are related with, and becomes attached to those sense objects. Such attachment constitutes preparation of the next body to be inhabited.
Between those who practice yoga and those who do not, an important difference is that those who practice yoga are able to see the reality of this process of transmigration, while those who do not practice yoga are unable to see it (15.7-11). Those who practice yoga are able to recognize the phenomenon of transmigration because they see that all living beings, as atemporal beings, are actually abiding in the supreme self, bhagavān, or puruṣottama. Yet due to their attachments, they are forced to continue transmigrating from one suffering body to another, lifetime after lifetime.
But also, such yogīs can appreciate the immanent power of puruṣottama; that the splendor of the sun, moon, and fire, are all his splendor; that it is he who preserves all beings with vigor and who, through the influence of the moon, nourishes all plants; that it is he who activates everyone’s digestive system; and that it is he who, dwelling in everyone’s heart, enables everyone to have memory, knowledge, and forgetfulness (15.12-15). Such yogīs are ready to comprehend the difference between the ultimate person and both perishing beings of this world and nonperishing beings of the transcendent world. Krishna concludes this chapter by praising those yogīs who know this greatest secret—the ultimate person—and who dedicate themselves entirely to him(15.16-20).