What is the field of these enjoying activities? This body. That we have discussed. Ksetra-ksetra-jna. Idam sariram ksetram ity abhidhiyate: "This body is the field of activities." So purusa, the living entities, has been entrapped by this material energy. That is called purusah prakrti-sthah. He is not required to stay in this material world, but he has decided to enjoy this material world. Therefore he is here. But he can give up. That is called liberty. That is called salvation. He can give up. Mukti. Mukti means... That is also described in the Srimad-Bhagavatam. Hitva anyatha-rupam svarupena vyavasthitih [SB 2.10.6]. That is called mukti. Muktir hitva anyatha-rupam. Here every living entity is situated anyatha-rupam. Anyatha-rupam means otherwise, which is not his nature. His nature is to serve, but he is staying here not as servant but as master.
Lecture on Bhagavad-gita 13.22, Bombay, 20 October, 1973