Text 21 

karya-karana-kartrtve
hetuh prakritir ucyate
purushah sukha-duhkhanam
bhoktrtve hetur ucyate

Translation

Nature is said to be the cause of all material causes and effects, whereas the living entity is the cause of the various sufferings and enjoyments in this world.

Commentary by Srila Prabhupada

The different manifestations of body and senses among the living entities are due to material nature. There are 8,400,000 different species of life, and these varieties are creations of the material nature. They arise from the different sensual pleasures of the living entity, who thus desires to live in this body or that. When he is put into different bodies, he enjoys different kinds of happiness and distress. His material happiness and distress are due to his body, and not to himself as he is. In his original state there is no doubt of enjoyment; therefore that is his real state. Because of the desire to lord it over material nature, he is in the material world. In the spiritual world there is no such thing. The spiritual world is pure, but in the material world everyone is struggling hard to acquire different kinds of pleasures for the body. It might be more clear to state that this body is the effect of the senses. The senses are instruments for gratifying desire. Now, the sum total—body and instrument senses—are offered by material nature, and as will be clear in the next verse, the living entity is blessed or damned with circumstances according to his past desire and activity. According to one’s desires and activities, material nature places one in various residential quarters. The being himself is the cause of his attaining such residential quarters and his attendant enjoyment or suffering. Once placed in some particular kind of body, he comes under the control of nature because the body, being matter, acts according to the laws of nature. At that time, the living entity has no power to change that law. Suppose an entity is put into the body of a dog. As soon as he is put into the body of a dog, he must act like a dog. He cannot act otherwise. And if the living entity is put into the body of a hog, then he is forced to eat stool and act like a hog. Similarly, if the living entity is put into the body of a demigod, he must act according to his body. This is the law of nature. But in all circumstances, the Supersoul is with the individual soul. That is explained in the Vedas (Mundaka Upanishad 3.1.1) as follows: dva suparna sayuja sakhayah. The Supreme Lord is so kind upon the living entity that He always accompanies the individual soul and in all circumstances is present as the Supersoul, or Paramatma.

Commentary by Sri Visvanatha Cakravarti Thakur

In this verse the Lord shows the jiva's connection with prakrti. Prakrti is the cause of the jiva's unfortunate condition by his misidentification with the body (karya), the senses which produce happiness and distress (karana) and the presiding deities of the senses (kartr). Prakrti, by association with the jiva, transforms into the form of body, senses and sense devatas, and, by its function of ignorance, it becomes the bestower of the jiva's misidentification.

The jiva (purusa), having the position as the enjoyer of the happiness and distress produced by prakrti, is also the cause of the connection.

The meaning is this. Even though the body, the senses, the sense devatas and the jiva's capacity for enjoyment (bhoktrtva) are all qualities of prakrti, because of the predominance of unconsciousness in the body, senses and sense devatas, and the predominance of consciousness in experiencing happiness and distress (bhoktr), the two get separately designated as causes according to predominance. According to this reasoning, it is said that prakrti is the cause, by producing the body, sense and sense devatas, and jiva is the cause by his capacity to experience happiness and distress.