The Gita begins its detailed review of the relation of Purusha, the witness consciousness and Prakriti, the active Nature, by defining and describing the field of action within which the Purusha exists, perceives, supports and causes action to occur.
Each of us experiences the world starting from a limited being conscious within a complex body that exists within a larger biosphere and ecosphere of the world and universe at large. Our immediate attention however is generally focused on the limited “self” that we perceive as separated and defined within our scope of immediate awareness. The Gita however, while acknowledging and starting from this point, does not in fact limit its definition of the “field” to the individual, but clearly includes the larger frame as part of the “field”. Thus, it is Prakriti that is the focus of attention when we describe the field of action.
Sri Aurobindo outlines the Gita’s view on this aspect: “…the whole of existence must be regarded as a field of the soul’s construction and action in the midst of Nature. The Gita explains the ksetram, field, by saying that it is this body which is called the field of the spirit, and in this body there is someone who takes cognizance of the field, ksetrajna, the knower of Nature.”
“It is evident, however, from the definitions that succeed that it is not the physical body alone which is the field, but all too that the body supports, the working of nature, the mentality, the natural action of the objectivity and subjectivity of our being. This wider body too is only the individual field; there is a larger, a universal, a world-body, a world-field of the same knower.”
“…physically, it is a microcosm in a macrocosm, and the macrocosm too, the large world too, is a body and field inhabited by the spiritual knower.”
The triple status of the Purusha, the “knower of the field”, involves initially an identification with the apparently separated being active in the world, and everything is evaluated and perceived from that standpoint. This awareness can expand to take in the wider scope of Nature under various circumstances of conscious growth and spiritual development. The second status provides a separation from the entire world of Nature, and takes the standpoint of an uninvolved, aloof, unmoving and unmoved Purusha. The third status holds both of these opposite standpoints together in one unified whole.
Sri Aurobindo, Essays on the Gita, Second Series, Part II, Chapter 13, The Field and Its Knower, pg. 398