A number of paths of understanding place the idea of “liberation” as the goal of human efforts. There are however different starting points and issues that arise based on variances between one philosophical structure and another. For instance, Mayavada treats the world as an illusion. The seeking for liberation is every bit as much a part of the illusion as those who are bound within the actions of the world. Abandonment of all relation to Nature is the only solution that Mayavada can provide.
Sankhya, grounded in observation and a sense of reality, cannot take this approach, and thus, cannot escape the issue of “what is liberated” and what the implications of that liberation must be. Having determined that “Nature is One”, Sankhya then has to focus on the relationship between the Witness Consciousness (Purusha) and the Nature (Prakriti).
Since the Purusha is defined as a passive witness, Sri Aurobindo points out that the “consent” or the “withdrawal of consent” of the Purusha is actually an act within Prakriti, not an act of the Purusha itself. He identifies this as a process within the Buddhi, the discriminating intelligence and will, one of the 24 principles of nature in the Sankhya system.
“Buddhi has been lending itself to the perceptions of the mind-sense; it has been busy discriminating and co-ordinating the operations of the cosmic energy and by the aid of the ego-sense identifying the Witness with her works of thought, sense and action.” Once Buddhi realises that it need not support this play any longer, the Purusha “…ceasing to be bound, no longer associates himself with the interest of the mind in the cosmic play.” Once this occurs, Prakriti loses its impetus and the 3 gunas fall into equilibrium and inaction.
Here we come to the crux of the problem that Sankhya observed. If there were only one Purusha and one Nature, this realisation would bring the entire universal action to an end; but they observed that one person achieving realisation did not seem to affect the universal action of Nature or the other beings who remained bounded and at work. Thus, they had to conclude that there were multiple Purushas so that the liberation of one of them would not bring the cosmos to an end!
Sri Aurobindo, Essays on the Gita, First Series, Chapter 8, Sankhya and Yoga, pp. 69-70,