The Gita proposes that there is a triple status of the soul. The Kshara Purusha is the soul involved in the activities of Nature. The Akshara Purusha is the soul in the status of being uninvolved, detached and unchanged by the activities of Nature. The Purushottama, the Supreme Soul, is the all-encompassing and overarching status that holds both of the others within itself in harmony, while exceeding them in its embracing Oneness.
The Upanishads refer to the “two birds” sitting on the common tree, one of which eats the sweet fruit, while the other looks on without eating. This image represents the statuses of the Kshara and the Akshara Purushas.
In order to truly understand how this triple status actually works, Sri Aurobindo takes them up serially, starting with the Kshara Purusha, the soul active in Nature. We see in Nature the manifestation of an Eternal, Supernal Being or Consciousness that manifests itself through all the forms, forces, actions, and through Time, Space and Circumstance, while still being beyond and above and Master of this all. The consciousness we recognize in Nature is the soul becoming self-aware because in reality, it is, as with all Nature, a portion of the Eternal, representing the Supreme Consciousness manifested and experiencing the forms and actions. “The inherent Power in her is yet other than what it thus seems to be; for, hidden in its truth, manifest in its appearances, it is the Kshara, the universal Soul, the spirit in the mutability of cosmic phenomenon and becoming, one with the Immutable and the Supreme. We have to arrive at the hidden truth behind its manifest appearances; we have to discover the Spirit behind these veils and to see all as the One, …individual, universal, transcendent. But this is a thing impossible to achieve with any completeness of inner reality, so long as we live concentrated in the inferior Nature. For in this lesser movement Nature is an ignorance, a Maya; she shelters the Divine within its folds and conceals him from herself and her creatures.”
“In the Kshara taken alone as a thing in itself, the mutable universe apart from the undivided Immutable and the Transcendent, there is no completeness of knowledge, no completeness of our being and therefore no liberation.”
The ability of the Divine to manifest a creation that is One and yet can be experienced from numerous individual standpoints “as if they are separate” is the sense of the play that brings about the Kshara Purusha. It is a form of exclusive concentration that sees the details without paying attention to the larger Existence.
Sri Aurobindo, Essays on the Gita, Second Series, Part II, Chapter 15, The Three Purushas, pp. 421-422