The Gita diverges from the Sankyha at this point, and it is an important distinction. The Sankhya holds that there is a duality between Purusha and Prakriti; one is either involved with Nature, or separated into a transcending consciousness of the pure silent witness. Thus, one is either fully involved in the manifested world and its beings, forces and actions, in the standpoint of the Kshara Purusha; or else, one abandons this whirl of existence to experience the silence, immutability, and eternity of the Akshara Purusha. This concept led eventually to what Sri Aurobindo calls ‘the refusal of the ascetic’, and the tendency among spiritually moved individuals throughout the world and throughout history to step back from the world, enter the cave, the desert or the monastery and concentrate on achieving the standpoint of the silent, immobile Self.
Sri Aurobindo reminds us that the Isha Upanishad (and others) provided a path to reconcile and harmonize the two statuses of consciousness. The Gita picks up on this unifying line of understanding and recognizes that a true understanding accepts the Oneness of both aspects. “But after all, the final experience is that of a unity of all beings which is not merely a community of experience, a common subjection to one force of Nature, but a oneness in the spirit, a vast identity of conscious being beyond all this endless variety of determination, behind all this apparent separativism of relative existence.”
“…it affirms with a strong insistence that the Akshara is the one self of all these many souls, and it is therefore evident that these two spirits are a dual status of one eternal and universal existence.”
“…the Isha tells us that Brahman is both the mobile and the immobile, is the One and the Many, is the Self and all existences…, is the Knowledge and the Ignorance, is the eternal unborn status and also the birth of existences, and that to dwell only on one of these things to the rejection of its eternal counterpart is a darkness of exclusive knowledge or a darkness of ignorance. It too insists like the Gita that man must know and must embrace both and learn of the Supreme in his entirety…, in order to enjoy immortality and live in the Eternal.”
Sri Aurobindo, Essays on the Gita, Second Series, Part II, Chapter 15, The Three Purushas, pp. 423-424