Prakriti means Nature. It is the material cause as well as the original cause of every thing in the manifested creation. Purusha is the silent Face. Prakriti is the activating Smile. Purusha is the pure, witnessing consciousness, while Prakriti is the evolving and transforming consciousness. In and through Prakriti is the fulfilment of the Cosmic Play.
Arjuna knew Sri Krishna as his dear cousin; he later knew him as his bosom friend; later still he knew him as his beloved Guru or spiritual Teacher. Here in this chapter he comes to know Sri Krishna as the Supreme Lord of the World. Krishna says, “Whenever unrighteousness is in the ascendent and righteousness is in the decline, I body myself forth. To protect and preserve the virtuous and put an end to the evil-doers, to establish Dharma, I manifest myself from age to age.” From these soul-stirring utterances of Sri Krishna, we immediately come to learn that He is both the Ultimate Knowledge and the Power Supreme. Confidently and smilingly, he is charging Arjuna with a high-voltage spiritual current from his great Power-House.