In 15.1, the samsāra tree was introduced. Brahman or Bhagavān was shown as the primary root, the visible universe as the branches, and the Vedic karma-kāṇḍa as the leaves that sustain the tree. 15.2 continues the same picture and gives more details about how the tree grows, how the jīva moves through it, and how bondage continues. The description of samsāra occupies the first two and a half verses of the chapter, and 15.2 is the detailed expansion of that tree imagery.

The verse says: tasya śākhāḥ adhaḥ ca ūrdhvaṃ prasṛtāḥ — the branches of that tree are spread below and above. “Above and below” also includes the middle. The branches are the various lokas and the bodies available in those lokas. The higher lokas and higher bodies, such as deva-śarīram, gandharva-śarīram, and pitṛ-śarīram, are the upper branches. Bhū-loka and the human body are the middle branch. Lower lokas and lower bodies, such as animal and plant bodies, are the lower branches. Thus the samsāra tree contains all possible fields of experience.

A very important point is made here: the body is not the jīva itself. The body is like a branch, a place of residence, a tenement. The jīva is the subtle body, the sūkṣma-śarīram, with reflected consciousness. At present, the jīva occupies the human branch and experiences pleasure and pain through the human body. When karma changes, the jīva leaves this body-branch. That is what we call death. Then, depending on karma, the jīva may occupy a higher branch, a similar branch, or a lower branch.

This means human life is not guaranteed upward progress. A person can rise, remain at the same level, or slip downward depending on the use of free will. The teaching compares this to a game of snake and ladder. Manuṣya-janma is precious because it gives a great opportunity, but it also carries responsibility. The goal is not to move from lower branch to higher branch. Even higher branches still belong to the tree. The real goal is to become a free bird — to gain mokṣa and be free from the tree itself.

The branches are described as guṇa-pravṛddhāḥ — nourished by the guṇas. The kind of body one gets is connected with sattva, rajas, and tamas. A sāttvika way of life prepares an uttama-śarīram, a higher body. A rājasa way of life prepares a madhyama-śarīram. A tāmasa way of life prepares an adhama-śarīram. This continues the teaching of Chapter 14: those established in sattva go upward; those dominated by rajas remain in the middle; those functioning in tamas go downward.

Then Bhagavān says the branches are viṣaya-pravālāḥ — their tender shoots are the sense objects. A shoot is the beginning of a branch. Similarly, the next body begins now in the form of our present responses to sense objects. Every sense object can create a desire. A seen object, heard sound, tasted food, touched comfort, praised status, attractive possession, or feared situation can produce kāma. Then kāma leads to karma, because desire pushes us into action. Karma produces puṇya and pāpa. Puṇya and pāpa determine the next śarīram. This is the chain: viṣaya → kāma → karma → puṇya-pāpa → next body.

The verse then speaks of roots spreading downward: adhaś ca mūlāni anusantatāni. In 15.1, Brahman was the primary root. Here, the roots are secondary roots. They are not named directly in the verse, but the commentators explain them as rāga-dveṣa-vāsanās — entrenched likes and dislikes. Every experience makes the mind classify: “This is welcome; this is not welcome.” In a few days, one can develop strong preferences and aversions. In a lifetime, these become countless.

Rāga leads to pravṛtti — going after what I like. Dveṣa leads to nivṛtti — avoiding or pushing away what I dislike. Pravṛtti and nivṛtti become karma. Karma produces puṇya and pāpa. Puṇya and pāpa produce punarjanma. Thus these secondary roots spread everywhere and keep the tree alive.

The verse ends with karmānubandhīni manuṣya-loke — these roots bind through karma in the human world. Manuṣya-loka is specially mentioned because human birth is karma-janma and the human world is karma-bhūmi. Other lokas are mainly bhoga-pradhāna, fields where past karma is experienced. But in human birth, fresh karma is generated through choice. Therefore, manuṣya-janma is both dangerous and sacred. It can bind further through rāga-dveṣa, or it can be used for viveka, vairāgya, and Brahma-jñānam.

15.2 therefore explains the machinery of samsāra. Bodies are branches. Guṇas nourish the branches. Sense objects are shoots. Rāga-dveṣa-vāsanās are secondary roots. Human life is the field where these roots produce karma. In 15.3, Bhagavān will say that this tree is not fully understandable in its beginning, middle, or end, and therefore it must be cut with the firm weapon of detachment.