1 Gita Sloka Every Day - Chapter 13 - Kshetra Kshetrajna Yoga - Sloka 20

The entire content of this mail is from Swami Adidevananda's translation of Ramanuja's  Gita  Bhashya and Swami Chidbhavananda's Bhagavad Gita, both published by Ramakrishna Mission

Prakriti and Purusha are External Verities 19-20

1 Gita Sloka  Every Day - Chapter 13 - Kshetra Kshetrajna Yoga - Sloka 20

Karya karana kartrtve hetuh prakritih uchyate I

Purushah sukha dukhanam bhoktrtve hetuh chyate II sloka 20

कार्य कारण कर्त्र्त्वे हेतुः प्रकृतिः उच्यते I

पुरुषः सुख दुखानां भोक्त्र्त्वे हेतुः उच्यते II श्लोक 20  

The prakriti is said to be the cause of the agency to the body (karya) and sense organs (karanam). The self is said to be the cause of experiencing pleasure and pain.

The karya means the body, the karanas means the instruments ie. the senses of perception and action plus the manas. In their operations, the prakriti, subservient to the self, is alone the causal factor. The sense is that their operations, which are the means of experience, have their foundation in prakriti, which has developed in the form of body subservient to the self. The agency of the self means that the self is the cause of the will (effort) to support the body. The self associated with the body is the cause for experiencing pain and pleasure. The meaning is that it is the seat of all the experiences.