Bhagavad Gita 13.31 (BG 13.31) | Kṣetra-kṣetrajña-vibhāga-yoga: Distinction between object Field and its Knower

By explaining the various concepts, Krishna points that all of them finally take the seeker to the Self in himself, the only changeless identity in the entire Creation. Everything else forms the vibrant Prakṛti, with its mobile and immobile aspects.

Prakṛti by itself will not be able to function. Purusha has to support everything big and small. Even the alternating experiences of sukha and duhkha are indisputably revealed by the Purusha.

To discern the unchanging Purusha and identify with Him, the understanding that all else comes within the orbit of ever-transforming Prakṛti, will be the best persuasion for the seeker. Remember Krishna’s first description of kshetra. He included sukha-duḥkhas, desire, hatred and awareness in it (13.7).

Purusha stands distinct from all forms of existence and expression. And he is within the body, denoted by the term ‘I’.