The Sankhya philosophy differs from that of the Gita particularly in the understanding and treatment of the position and role of the Purusha, the true Self, the Witness consciousness. The Sankhya essentially sets up a duality of Purusha and Prakriti, the Purusha constituting the non-acting, silent witness that provides the sanction to Nature, and the Prakriti as the executive Nature that “acts” under the passive sanction, but non-intervention of the Purusha. The Purusha’s role is to either provide a sanction, at which point it is at least apparently bound by the actions of the modes of Nature, or withdraw the sanction, which leads to renunciation of action and works in the world, and a dissolution into the pure, silent witness consciousness.
The Gita, however, does not rest satisfied with this conclusion and the implications of this duality. The Gita presents the idea that the Purusha can go beyond passive acquiescence in the action of Prakriti to active mastery over Nature. This comes about through the key concept of there being a larger being that carries within itself both Purusha and Prakriti as two complementary aspects of itself. When we are able to pass beyond the frame that encompasses Purusha and Prakriti, we are able to experience the true freedom of the Purusha and exercise mastery over the action of Prakriti.
Sri Aurobindo examines the Gita’s position: “In the Sankhya Soul and Nature are two different entities, in the Gita they are two aspects, two powers of one self-existent being; the Soul is not only giver of the sanction, but lord of Nature, Ishwara, through her enjoying the play of the world, through her executing divine will and knowledge in a scheme of things supported by his sanction and existing by his immanent presence, existing in his being, governed by the law of his being and by the conscious will within it. To know, to respond to, to live in the divine being and nature of this Soul is the object of withdrawing from the ego and its action. One rises then above the lower nature of the Gunas to the higher divine nature.”
Sri Aurobindo, Essays on the Gita, First Series, Chapter 22, Beyond the Modes of Nature, pp. 217-218